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AbstractThis study aimed to enhance the extracellular polymeric substances (EPS) production of Virgibacillus dokdonensis VITP14 and explore its antioxidant potential. EPS and biomass production by VITP14 strain were studied under different culture parameters and media compositions using one factor at a time method. Among different nutrient sources, glucose and peptone were identified as suitable carbon and nitrogen sources. Furthermore, the maximum EPS production was observed at 5% of inoculum size, 5 g/L of NaCl, and 96 h of fermentation. Response surface methodology was employed to augment EPS production and investigate the optimal levels of nutrient sources with their interaction. The strain was observed to produce actual maximum EPS of about 26.4 g/L for finalized optimum medium containing glucose 20 g/L, peptone 10 g/L, and NaCl 50 g/L while the predicted maximum EPS was 26.5 g/L. There was a nine fold increase in EPS production after optimization study. Additionally, EPS has exhibited significant scavenging, reducing, and chelating potential (>85%) at their higher concentration. This study imparts valuable insights into optimizing moderately halophilic bacterial EPS production and evaluating its natural antioxidant properties. According to findings, V. dokdonensis VITP14 was a promising isolate that will provide significant benefits to biopolymer producing industries. [ABSTRACT FROM AUTHOR]

[Objective] To explore the effects of different enrichment time, culture salinity, dilution gradient and medium on the diversity of culturable halophilic bacteria in chloride type Kunteyi high salt lake, to determine the best isolation and culture conditions for halophilic bacteria, and to explore more resources of environmental halophilic bacteria. [Method] The mixed water and mud samples were collected from Kunteyi Salt Lake, and 7 media with 2 salinities of 10% and 18% NaCl were selected to isolate the halophilic bacteria by enrichment culture, plate dilution coating and plate zonal delineation methods. The phylogenetic status of the strains was determined by 16S rRNA gene sequencing and BLAST sequence comparison. At the same time, culture-free Illumina MiSeq high-throughput sequencing technology was used to analyze the bacterial community structure diversity in Kunteyi Salt Lake. [Result] A total of 39 phyla, 64 classes, 101 orders, 219 families and 703 genera of bacteria were identified in the culture-free samples collected from Kunteyi Salt Lake. Among them, Pseudomonadota, Bacillota, Bacteroidota and Actinomycetota were the main dominant phyla. According to the size, shape, color, gloss, transparency, texture, uplift status, and marginal characteristics of the colonies, 436 strains of halophilic bacteria were isolated, belonging to 3 phyla, 3 classes, 6 orders, 9 families, 28 genera and 77 species, among which 16 strains were potential new species. The three phyla were Bacillota, Pseudomonadota and Actinomycetota, all of which were the dominant phyla in the culture-free results. At the genus level, Bacillus, Halomonas, Halobacillus, Virgibacillus and Salicola were the dominant genera. Tuberibacillus, Rossellomorea and Glutamicibacter were isolated from the salt lake for the first time. The number of strains isolated by 18% NaCl was significantly lower than that by 10% NaCl, and the diversity was low. Sporolactobacillaceae was the unique bacteriaceae isolated under this condition. Among the 7 media, 1/2 RCA medium had the best isolation results. The optimal enrichment time was 0, 7 and 60 d, and the optimal sample dilution gradients were 10-2 and 10-3. [Conclusion] There were 3 phyla, 3 classes, 6 orders, 9 families, 28 genera and 77 species of halophilic bacteria isolated from Kunteyi Salt Lake. The diversity of culturable halophilic bacteria could be significantly improved by using various culture media and different salinities, enrichment culture time and dilution gradients. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Petroleum-based plastics produce tremendous amounts of plastic waste every year, which contributes to environmental problems. Biological polymers, such as polyhydroxybutyrate, have caught attention as an ecofriendly substitute to petroleum-based plastics. The present study focused on the production, enhancement, and characterization of polyhydroxybutyrate from the prospective local bacterium Halomonas elongata. This research aimed to develop an environmentally sustainable material for reducing the accumulation of plastic waste in the ecosystem.METHODS: A local bacterial strain from Mud Crater Bledug Kuwu, Grobogan, Central Java, Indonesia, was isolated and identified as Halomonas elongata. Nile red staining method confirmed that this bacterium accumulated polyhydroxybutyrate. The effect of incubation time, sodium chloride concentration, nitrogen, and carbon sources were evaluated via gas chromatography to enhance its productivity. The functional groups of isolated polyhydroxybutyrate were analyzed using nuclear magnetic resonance and Fourier transform infrared spectroscopy. Morphology and composition were demonstrated by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Thermogravimetric analysis, differential thermogravimetry, and differential thermal analysis were used to analyze thermal stability.FINDINGS: Halomonas elongata produced polyhydroxybutyrate utilizing glucose as a carbon source, as evidenced by orange-fluorescence colonies under ultraviolet light. The optimum condition of polyhydroxybutyrate production was achieved when the bacterium was cultivated in a high medium containing 5 percent sodium chloride, 0.2 percent yeast extract, and 5 percent glucose (as measured by weight per volume) after 72 hours of incubation. The maximum polyhydroxybutyrate production in this medium reached 2.93 ± 0.03 gram per liter dry cell weight and 78 ± 1 percent polyhydroxybutyrate concentration. Structural elucidation studies revealed that the biopolymer produced by this bacterium was high-purity polyhydroxybutyrate, as proven by the presence of functional groups and proton resonance signals in the monomer structure. The isolated polyhydroxybutyrate consisted of 14 percent carbon and 86 percent oxygen. Thermal stability analysis showed that the isolated polyhydroxybutyrate had a maximum decomposition temperature of 270 degrees Celsius. Micrographically, the isolated polyhydroxybutyrate appeared as a sheet structure with interconnected fibers measuring 0.7–0.8 micromter in length. This finding also demonstrates that the isolated polyhydroxybutyrate has good thermal stability given that fibers linked each polyhydroxybutyrate molecule, which boosted the structure of polyhydroxybutyrate.CONCLUSION: This study successfully synthesized polyhydroxybutyrate using a local strain of Halomonas elongata, with glucose as a carbon source. Physicochemical characterization revealed that polyhydroxybutyrate from this bacterium has a high thermal stability. The yield of polyhydroxybutyrate can be increased through the improvement of production parameters. This research emphasizes an important milestone toward the large-scale production of polyhydroxybutyrate for application as food packaging while reducing environmental issues.

Anthranilic acid (AA) holds significant importance in the chemical industry. It serves as a crucial building block for the amino acid tryptophan by manipulating the tryptophan biosynthesis pathway, it is possible to increase the production of anthranilic acid. In this study, we utilized metabolic engineering approaches to produce anthranilic acid from the halophilic bacterium Virgibacillus salarius MML1918. The halophilic bacteria were grown in an optimized production medium, and mass production of secondary metabolites was made in ATCC medium 1097 Proteose peptone—for halophilic bacteria and subjected to column chromatography followed by sub-column chromatography the single band for the purified compound was confirmed. Further, various spectral analyses were made for the partially purified compounds, and fluorescence microscopy for fungal cell observation was performed. The purified compound was confirmed by single crystal X-ray diffraction (XRD) analysis, and it was identified as 2-amino benzoic acid. The Fourier transform infrared Spectroscopy (FT-IR) spectrum and nuclear magnetic resonance (NMR) spectrum also confirm the structural characteristic of 2-amino benzoic acid. The UV–Vis absorption spectrum of AA shows the maximum absorption at 337.86 nm. The emission spectrum of 2-amino benzoic acid showed the maximum emission at 453 nm. The bio-imaging application of 2-amino benzoic acid was examined with fungal mycelium of Rhizoctonia solani. It was effectively bound and emitted the blue color at the concentration of 200 and 300 µg/mL. The halophilic bacterium (V. salarius), may have unique metabolic pathways and requirements compared to non-halophilic organisms, to produce AA effectively. This could have implications for industrial biotechnology, particularly in manufacturing environments where high salt concentrations are present and also it can be used as bio-imaging agent. [ABSTRACT FROM AUTHOR]

Microbial natural products from microbes in extreme environments, including haloarchaea, and halophilic bacteria, possess a huge capacity to produce novel antibiotics. Additionally, enhanced isolation techniques and improved tools for genomic mining have expanded the efficiencies in the antibiotic discovery process. This review article provides a detailed overview of known antimicrobial compounds produced by halophiles from all three domains of life. We summarize that while halophilic bacteria, in particular actinomycetes, contribute the vast majority of these compounds the importance of understudied halophiles from other domains of life requires additional consideration. Finally, we conclude by discussing upcoming technologies- enhanced isolation and metagenomic screening, as tools that will be required to overcome the barriers to antimicrobial drug discovery. This review highlights the potential of these microbes from extreme environments, and their importance to the wider scientific community, with the hope of provoking discussion and collaborations within halophile biodiscovery. Importantly, we emphasize the importance of bioprospecting from communities of lesser-studied halophilic and halotolerant microorganisms as sources of novel therapeutically relevant chemical diversity to combat the high rediscovery rates. The complexity of halophiles will necessitate a multitude of scientific disciplines to unravel their potential and therefore this review reflects these research communities. [ABSTRACT FROM AUTHOR]

Salinity is one of the main factors causing soil deterioration, making it unsuitable for agriculture. It is well documented that the application of halotolerant and halophilic plant growth-promoting bacteria (PGPR: plant growth-promoting rhizobacteria) with biological control activities as an inoculant of cultivated plants offers a biological alternative to the use of agrochemicals, particularly when subjected to salt stress. From this perspective, 70 bacterial strains were isolated from saline soils (sebkha) in arid and semi-arid areas of Eastern Algeria. Three isolates were selected based on their ability to produce bioactive molecules allowing them to promote plant growth, such as hydrolytic enzymes, indole acetic acid (auxin-phytohormone), HCN, NH3, etc. Two of these isolates belonged to the genus Serratia and the third was a halophilic Halomonas bacteria. These bacteria were identified based on their 16S rDNA sequences. Antagonism tests against phytopathogenic fungi were carried out. The identification of the antifungal molecules produced by these bacteria was determined using high-performance liquid chromatography. These bacteria can inhibit mycelial development against phytopathogenic fungi with rates reaching 80.67% against Botrytis cinerea, 76.22% against Aspergillus niger, and 66.67% against Fusarium culmorum for Serratia sp. The strain Halomonas sp. inhibited mycelial growth through the production of volatile substances of Aspergillus niger at 71.29%, Aspergillus flavus at 75.49%, and Penicillium glabrum at a rate of 72.22%. The identification of the antifungal molecules produced by these three bacteria using HPLC revealed that they were polyphenols, which makes these strains the first rhizobacteria capable of producing phenolic compounds. Finally, pot tests to determine the effectiveness of these strains in promoting wheat growth under salinity stress (125 mM, 150 mM, and 200 mM) was carried out. The results revealed that a consortium of two isolates (Serratia sp. and Halomonas sp.) performed best at 125 mM. However, at higher concentrations, it was the halophilic bacteria Halomonas sp. that gave the best result. In all cases, there was a significant improvement in the growth of wheat seedlings inoculated with the bacteria compared to non-inoculated controls. [ABSTRACT FROM AUTHOR]

The isolated halophilic bacterial strain Halovibrio variabilis TG-5 showed a good performance in the pretreatment of coal gasification wastewater. With the optimum culture conditions of pH = 7, a temperature of 46 °C, and a salinity of 15%, the chemical oxygen demand and volatile phenol content of pretreated wastewater were decreased to 1721 mg/L and 94 mg/L, respectively. The removal rates of chemical oxygen demand and volatile phenol were over 90% and 70%, respectively. At the optimum salinity conditions of 15%, the total yield of intracellular compatible solutes and the extracellular transient released yield under hypotonic conditions were increased to 6.88 g/L and 3.45 g/L, respectively. The essential compatible solutes such as l-lysine, l-valine, and betaine were important in flocculation mechanism in wastewater pretreatment. This study provided a new method for pretreating coal gasification wastewater by halophilic microorganisms, and revealed the crucial roles of compatible solutes in the flocculation process. [ABSTRACT FROM AUTHOR]

Background: Halophilic bacteria are studied extensively to explore molecular basis of adaptation, enzymatic potential, drug resistance and their other biotechnological implications. Their ability to survive in hypersaline condition is often linked to the potential of biosynthesizing a well-known compatible solute, namely ectoine. Aim: In this study, four bacterial strains, which were previously identified from hypersaline environment were studied for their growth pattern and ectoine biosynthesis protein expression under varying NaCl concentrations. In addition, antibiotic susceptibility of the strains was also investigated. Methods: The growth pattern of the bacterial strains were studied in Luria-Bertani broth supplemented with different NaCl concentrations. Bradford method was employed for protein estimation, and optical densities of the samples were quantified through UV-Vis spectrophotometer. Moreover, expression of the proteins responsible for biosynthesis of ectoine were detected through SDS-PAGE, and disc diffusion method was used for profiling the antibiotic resistance of the strains. Results: The results indicated distinct growth patterns, with each strain demonstrating preferences for specific salinity levels. Notably, Staphylococcus cohnii strain F exhibited optimal growth at 10% NaCl, while Jeotgalicoccus huakuii strain 3.7 thrived at 15% NaCl. Total protein analysis revealed a consistent trend of decreasing protein content with rising NaCl concentrations, elucidating a potential adaptive strategy. Staphylococcus cohnii strain F stood out, maintaining higher protein levels at 20% NaCl, indicative of unique adaptive mechanisms. Antibiotic susceptibility testing uncovered diverse resistance profiles, emphasizing the strain-specific nature of responses. The expression of ectoine biosynthesis genes in S. cohnii strain F underlines its adaptive advantage in high salinity. Conclusion: The findings contribute not only to basic microbial physiology knowledge but also hold implications for biotechnological applications and clinical practices, emphasizing the importance of tailored approaches in antibiotic therapy and highlighting the strain-specific nature of bacterial adaptations. [ABSTRACT FROM AUTHOR]

Halomonas pacifica CARE-V15 was isolated from the southeastern coast of India to determine its genome sequence. Secondary metabolite gene clusters were identified using an anti-SMASH server. The concentrated crude ethyl acetate extract was evaluated by GC-MS. The bioactive compound from the crude ethyl acetate extract was fractionated by gel column chromatography. HPLC was used to purify the 3,6-diisobutyl-2,5-piperazinedione (DIP), and the structure was determined using FTIR and NMR spectroscopy. Purified DIP was used in an in silico molecular docking analysis. Purified DIP exhibits a stronger affinity for antioxidant genes like glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GSR). Using in silco molecular docking analysis, the protein-ligand binding affinities of GSR (-4.70 kcal/mol), GST (-5.27 kcal/mol), and GPx (-5.37 kcal/mol) were measured. The expression of antioxidant genes were investigated by qRT-PCR. The in vivo reactive oxygen species production, lipid peroxidation, and cell death levels were significantly (p = 0.05) increased in OA-induced group, but all these levels were significantly (p = 0.05) decreased in the purified DIP pretreated group. Purified DIP from halophilic bacteria could thus be a useful treatment for neurological disorders associated with oxidative stress. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are synthesized by a variety of microorganisms as intracellular storage granules under imbalanced nutrition and excess carbon. Carbon sources are key contributors to the high cost of PHA production, hence the need for exploration of cheap and sustainable raw materials for bacteria fermentation. In the present study, Halomonas alkalicola strain Ext isolated from a hypersaline lake in Kenya was assessed for its ability to utilize fruit peels hydrolysates (FPH) as sole carbon sources for PHA production. Sugars were extracted from dried peels of banana, mango, orange, and pineapple fruits through mechanical pretreatment and dilute acid hydrolysis. Fruit peels pretreated with 3 % H2SO4 at 121℃ were utilized for shake flask fermentation to produce PHAs by Halomonas alkalicola Ext. At optimal C:N ratios of between 20:1 and 30:1, the bacterium could produce up to 0.45±0.03, 0.394±0.12, 0.39±0.05, and 0.28±0.0 g/L of PHAs from hydrolysates of orange peels, mango peels, banana peels, and pineapple peels, respectively. A maximum PHA content of 16.92 % was achieved on orange peels hydrolysates with 4 % substrate loading. Monomer analysis with gas chromatography-mass spectrometry (GC-MS) revealed that the bacterium produced a copolymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with 3-hydroxyvalerate (3HV) contents of 5.77 %, 6.08 %, 6.79 %, 6.845 %, for orange peels, pineapple peels, mango peels and banana peels substrates, respectively. The findings of this study suggest that fruit peels waste is a potential feedstock for sustainable production of PHAs by Halomonas alkalicola.

Soil salinization is negatively affecting soils globally, and the spread of this problem is of great concern due to the loss of functions and benefits offered by the soil resource. In the present study, we explored the diversity of halophilic and halotolerant microorganisms in the arable fraction of a sodic–saline soil without agricultural practices and two soils with agricultural practices (one sodic and one saline) near the geothermal area "Los Negritos" in Villamar, Michoacán state. This was achieved through their isolation and molecular identification, as well as the characterization of their potential for the production of metabolites and enzymes of biotechnological interest under saline conditions. Using culture-dependent techniques, 62 halotolerant and moderately halophilic strains belonging to the genera Bacillus, Brachybacterium, Gracilibacillus, Halobacillus, Halomonas, Kocuria, Marinococcus, Nesterenkonia, Oceanobacillus, Planococcus, Priestia, Salibactetium, Salimicrobium, Salinicoccus, Staphylococcus, Terribacillus, and Virgibacillus were isolated. The different strains synthesized hydrolytic enzymes under 15% (w/v) of salts, as well as metabolites with plant-growth-promoting (PGP) characteristics, such as indole acetic acid (IAA), under saline conditions. Furthermore, the production of biopolymers was detected among the strains; members of Bacillus, Halomonas, Staphylococcus, and Salinicoccus showed extracellular polymeric substance (EPS) production, and the strain Halomonas sp. LNSP3E3-1.2 produced polyhydroxybutyrate (PHB) under 10% (w/v) of total salts. [ABSTRACT FROM AUTHOR]

Saltpans in South India experience intense sunlight and ultraviolet radiation (UV). Therefore, it was hypothesized that halophilic bacteria living there could tolerate UV radiation. To test this, sediment and water samples from the Marakkanam Saltpan were collected and exposed to an artificial UV-B lamp. After irradiation, an aliquot of the sample was spread on nutrient agar (prepared in sterilized source water), and two bacterial strains were obtained, named SBO and SBY. Based on 16S rRNA gene phylogeny, these strains were identified as Bacillus sp. and Pontibacillus salipaludis, respectively. Another aliquot of the UV-B-exposed sample was inoculated into the nutrient broth (in sterilized source water), and incubated for a week in the dark. Later, it was subjected to Illumina MiSeq-based sequencing for the V3-V4 region (16S rRNA gene). Results revealed the presence of 13 bacterial phyla. However, the phylum Bacillota (48.59%) and Pseudomonadota (27.36%) accounted for more than 75% of the diversity. Pontibacillus was the most abundant genus, accounting for 44% of total bacterial diversity. The whole genome of P. salipaludis was sequenced on Illumina HiSeqX to decipher possible genes and pathways involved in UV-B tolerance. The genome size was estimated to be 4.05 MB, with a mean G + C content of 40.82%. RASTtk-based genome annotation revealed 4217 coding sequences and 78 RNAs. Related to the UV-B tolerance, sixteen genes involved in carotenoid and prodigiosin biosynthetic pathways were found. antiSMASH showed the presence of terpene-type carotenoids. More than sixty genes involved in various DNA repair pathways were found. [ABSTRACT FROM AUTHOR]

Biotreatment of oily sludge and the involved microbial communities, particularly in saline environments, have been rarely investigated. We enriched a halophilic bacterial consortium (OS-100) from petroleum refining oily sludge, which degraded almost 86% of the aliphatic hydrocarbon (C10-C30) fraction of the oily sludge within 7 days in the presence of 100 g/L NaCl. Two halophilic hydrocarbon-degrading bacteria related to the genera Chromohalobacter and Halomonas were isolated from the OS-100 consortium. Hydrocarbon degradation by the OS-100 consortium was relatively higher compared to the isolated bacteria, indicating potential synergistic interactions among the OS-100 community members. Exclusion of FeCl2, MgCl2, CaCl2, trace elements, and vitamins from the culture medium did not significantly affect the hydrocarbon degradation efficiency of the OS-100 consortium. To the contrary, hydrocarbon biodegradation dropped from 94.1 to 54.4% and 5% when the OS-100 consortium was deprived from phosphate and nitrogen sources in the culture medium, respectively. Quantitative PCR revealed that alkB gene expression increased up to the 3rd day of incubation with 11.277-fold, consistent with the observed increments in hydrocarbon degradation. Illumina-MiSeq sequencing of 16 S rRNA gene fragments revealed that the OS-100 consortium was mainly composed of the genera Halomonas, Idiomarina, Alcanivorax and Chromohalobacter. This community structure changed depending on the culturing conditions. However, remarkable changes in the community structure were not always associated with remarkable shifts in the hydrocarbonoclastic activity and vice versa. The results show that probably synergistic interactions between community members and different subpopulations of the OS-100 consortium contributed to salinity tolerance and hydrocarbon degradation. Key points: • A halophilic bacterial consortium efficiently degrades oily sludge hydrocarbons. • Nitrogen starvation and high salinity have the greatest impact on hydrocarbon loss. • Change in the consortium structure is not a prerequisite to shift biodegradation. [ABSTRACT FROM AUTHOR]

Halophilic bacterial strains, designated SG2L-4T, SB1M4, and SB2L-5, were isolated from jeotgal, a traditional Korean fermented food. Cells are Gram-stain-negative, aerobic, non-motile, rod-shaped, catalase-positive, and oxidase-negative. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain SG2L-4T is closely related to Halomonas garicola KACC 18117T with a similarity of 96.2%. The complete genome sequence of strain SG2L-4T was 3,227,066  bp in size, with a genomic G  +  C content of 63.3  mol%. The average nucleotide identity and digital DNA–DNA hybridization values between strain SG2L-4T and H. garicola KACC 18117T were 90.5 and 40.7%, respectively. The optimal growth conditions for strain SG2L-4T were temperatures between 30 and 37°C, a pH value of 7, and the presence of 10% (w/v) NaCl. The polar lipids identified included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unknown phospholipid, an unknown glycolipid, and an unknown polar lipid. The major cellular fatty acids were C16:0, summed features 8 (C18:1 ω6c and/or C18:1 ω7c), C19:0 cyclo ω8c, and summed features 3 (C16:1 ω6c and/or C16:1 ω7c). The predominant respiratory quinone was ubiquinone with nine isoprene units (Q-9). Based on the phenotypic, genotypic, and chemotaxonomic results, strain SG2L-4T represents a novel species within the genus Halomonas, for which the name Halomonas piscis sp. nov. is proposed. The type strain is SG2L-4T (=KCTC 92842T   =  JCM 35929T ). Functional annotation of the genome of strain SG2L4T confirmed the presence of exopolysaccharide synthesis protein (ExoD) and capsular polysaccharide-related genes. Strain SG2L-4T also exhibited positive results in Molisch’s test, indicating the presence of extracellular carbohydrates and exopolysaccharides (EPS) production. These findings provide valuable insights into the EPS-producing capabilities of H. piscis sp. nov. isolated from jeotgal, contributing to understanding its potential roles in food and biotechnological applications. [ABSTRACT FROM AUTHOR]

The salinization of soils is a growing agricultural concern worldwide. Irrigation practices, drought, and climate change are leading to elevated salinity levels in many regions, resulting in reduced crop yields. However, there is potential for a solution in the microbiome of halophytes, which are naturally salt-tolerant plants. These plants harbor a salt-tolerant microbiome in their rhizosphere (around roots) and endosphere (within plant tissue). These bacteria may play a significant role in conferring salt tolerance to the host plants. This leads to the possibility of transferring these beneficial bacteria, known as salt-tolerant plant-growth-promoting bacteria (ST-PGPB), to salt-sensitive plants, enabling them to grow in salt-affected areas to improve crop productivity. In this review, the background of salt-tolerant microbiomes is discussed and their potential use as ST-PGPB inocula is explored. We focus on two Gram-negative bacterial genera, Halomonas and Kushneria, which are commonly found in highly saline environments. These genera have been found to be associated with some halophytes, suggesting their potential for facilitating ST-PGPB activity. The study of salt-tolerant microbiomes and their use as PGPB holds promise for addressing the challenges posed by soil salinity in the context of efforts to improve crop growth in salt-affected areas. [ABSTRACT FROM AUTHOR]

The salinity of the soil exerts an adverse effect on plant development and yield. However, amid saline stress, certain halophilic bacteria enhance the growth of plants. In this investigation, the mangrove halophyte Avicennia marina's (A. marina) rhizosphere soil was used as the source for the isolation of halophilic bacteria. The isolates' growth capacity at different pH, salinity, temperature, and polyethylene glycol (PEG) was assessed, and it was found that 56% showed growth in media supplemented with 2–7.5% NaCl; 50% showed efficient growth at pH 6–8, 62% grow optimally at temperature 25–35 °C, and about 88% showed growth in media with 5% PEG. The isolates possess growth-promoting traits evidenced by nitrogen fixation (18%), ammonia production (31%), phosphate solubilization (88%), zinc solubilization (44%), and indole acetic acid (IAA) (88%) production. The isolates can produce extracellular enzymes, viz., protease (88%), amylase (62%), cellulase (56%), and lipase (31%). The bacterial isolate S1B1 that displayed maximum plant growth-promoting traits was selected as the potent and subjected to plant growth promotion studies. The potent isolate S1B1 enhances Solanum lycopersicum's germination under different salinity compared to untreated seeds with germination of 64% at the maximum concentration of 2% NaCl. The potential halophilic plant growth-promoting rhizobacteria (PGPR) isolate was determined as Rossellomorea aquimaris (R. aquimaris) by 16s rRNA analysis. The results demonstrated that R. aquimaris recovered from the rhizosphere of halophyte A. marina found possible applications for enhancing plant development and productivity in salinity-affected soils. [ABSTRACT FROM AUTHOR]

The raspberry (Rubus idaeus) is the main crop of Jocotepec municipality, being dedicated to protected agriculture, chemical fertilization causes soil salinization, which results in the crop's not developing its maximum potential. To evaluate the effect of halophilic bacteria as a sustainable strategy to reduce soil salinity in raspberry cultivation, the present research assessed a production unit located at the Jocotepec Municipality, Jalisco state, Mexico. The evaluated halophilic bacteria treatments were doses of 7 L/ha, 5 L/ha, and 3 L/ha plus an absolute control, on three intervals - of 15 days application in saturated furrow irrigation. The assessed soil variables were pH and EC; in the plants: plant height, number of loaders, stem diameter, and number of boxes produced. The evaluation of the effect of halophilic bacteria on the quantitative variables was carried out with an ANOVA in the SAS® Studio 2023 software, in a completely randomized block design, after complying with normality of residuals and homogeneity of variances assumptions associated with the Tukey means comparison statistical test (p=0.05). The results show a direct effect of the halophilic bacteria dosage on the soil EC decrease, from 2.35 ds/m (Control) to 1.81 ds/m (Dose 5 L/ha), values equivalent to light salinity (X2 ds/m). Regarding the agronomic variables, improvements were evident in the evaluated characteristics. [ABSTRACT FROM AUTHOR]

A Gram-stain-negative, strictly aerobic, motile, slightly curved rod-shaped bacterium with multiple flagella, designated strain EGI 63088T, was isolated from a bulk soil of Kalidium foliatum, collected from Wujiaqu in Xinjiang Uighur Autonomous Region, PR China. The optimal growth temperature, salinity, and pH for strain EGI 63088T growth were 30 °C, 3% (w/v) NaCl and 8, respectively. Phylogenetic analysis using 16S rRNA gene sequences indicated that strain EGI 63088T showed the highest sequence similarities to Halomonas heilongjiangensis 9-2T (97.94%), H. lysinitropha 3(2)T (97.51%), and H. daqiaonensis CGMCC 1.9150T (97.08%). The average nucleotide identity and digital DNA–DNA hybridization values between the strain EGI 63088T and H. heilongjiangensis 9-2T were 89.03 and 41.10%, respectively. The DNA G + C content of the genome for strain EGI 63088T was 66.3 mol%. The most prevalent antibiotic resistance and virulence-related genes in Halomonas genomes were Streptomyces cinnamoneu EF-Tu mutant, pilT, and cheY, respectively. The predominant fatty acids of strain EGI 63088T were summed feature 8 (C18: 1ω6c and/or C18: 1ω7c), summed feature 3 (C16: 1ω6c and/or C16: 1ω7c), and C16: 0; its major respiratory quinone was ubiquinone-9 (Q-9), and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. According to the above results, strain EGI 63088T is considered a novel species of the genus Halomonas, for which the name Halomonas flagellata sp. nov. is proposed. The type strain is EGI 63088T (= KCTC 92047T = CGMCC 1.19133T). [ABSTRACT FROM AUTHOR]

Salinity is one of the main factors causing soil deterioration, making it unsuitable for agriculture. It is well documented that the application of halotolerant and halophilic plant growth-promoting bacteria (PGPR: plant growth-promoting rhizobacteria) with biological control activities as an inoculant of cultivated plants offers a biological alternative to the use of agrochemicals, particularly when subjected to salt stress. From this perspective, 70 bacterial strains were isolated from saline soils (sebkha) in arid and semi-arid areas of Eastern Algeria. Three isolates were selected based on their ability to produce bioactive molecules allowing them to promote plant growth, such as hydrolytic enzymes, indole acetic acid (auxin-phytohormone), HCN, NH3, etc. Two of these isolates belonged to the genus Serratia and the third was a halophilic Halomonas bacteria. These bacteria were identified based on their 16S rDNA sequences. Antagonism tests against phytopathogenic fungi were carried out. The identification of the antifungal molecules produced by these bacteria was determined using high-performance liquid chromatography. These bacteria can inhibit mycelial development against phytopathogenic fungi with rates reaching 80.67% against Botrytis cinerea, 76.22% against Aspergillus niger, and 66.67% against Fusarium culmorum for Serratia sp. The strain Halomonas sp. inhibited mycelial growth through the production of volatile substances of Aspergillus niger at 71.29%, Aspergillus flavus at 75.49%, and Penicillium glabrum at a rate of 72.22%. The identification of the antifungal molecules produced by these three bacteria using HPLC revealed that they were polyphenols, which makes these strains the first rhizobacteria capable of producing phenolic compounds. Finally, pot tests to determine the effectiveness of these strains in promoting wheat growth under salinity stress (125 mM, 150 mM, and 200 mM) was carried out. The results revealed that a consortium of two isolates (Serratia sp. and Halomonas sp.) performed best at 125 mM. However, at higher concentrations, it was the halophilic bacteria Halomonas sp. that gave the best result. In all cases, there was a significant improvement in the growth of wheat seedlings inoculated with the bacteria compared to non-inoculated controls.

In this study, we used culture-independent analysis based on 16S rRNA gene amplicons and metagenomics to explore in depth the microbial communities and their metabolic capabilities of artisanal brine cheeses made in the North Caucasus. Additionally, analysis of organic acid profiles was carried out for cheese characterization. Twelve cheese samples (designated as 05SR–16SR) from various artisanal producers were taken from five different villages located in Northern Ossetia–Alania (Russia). These cheeses were made using methods based on cultural traditions inherited from previous generations and prepared using a relatively uncontrolled fermentation process. The microbial diversity of Caucasus artisanal cheeses was studied for the first time. The results showed a diverse composition in all cheeses, with Bacillota (synonym Firmicutes) (9.1–99.3%) or Pseudomonadota (synonym Proteobacteria) (0.2–89.2%) prevalence. The microbial communities of the majority of the studied cheeses were dominated by lactic acid bacteria (LAB) genera, like Lactococcus (10.3–77.1% in 07SR, 09SR, 10SR, 11SR, 13SR, 15SR, 16SR), Lactobacillus (54.6% in 09SR), Streptococcus (13.9–93.9% in 11SR, 13SR, 14SR, 15SR), Lactiplantibacillus (13.4–30.6% in 16SR and 07SR) and Lentilactobacillus (5.9–14.2% in 09SR, 10SR and 13SR). Halophilic lactic acid bacteria belonging to the Tetragenococcus genus accounted for 7.9–18.6% in 05SR and 06SR microbiomes. A distinctive feature of Ossetia cheese microbiomes was the large variety of halophilic proteobacteria, and in some cheeses they prevailed, e.g., Chromohalobacter (63–76.5% in 05SR and 06SR), Psychrobacter (10–47.1% in 08SR, 11SR, 12SR), Halomonas (2.9–33.5% in 06SR, 08SR, 11SR and 12SR), Marinobacter (41.9% in 12SR) or Idiomarina (2.9–14.4% in 06SR, 08SR and 11SR samples). Analysis of the genomes assembled from metagenomes of three cheeses with different bacterial composition revealed the presence of genes encoding a variety of enzymes, involved in milk sugar, proteins and lipid metabolism in genomes affiliated with LAB, as well as genes responsible for beneficial bioamine and bacteriocin synthesis. Also, most of the LAB did not contain antibiotic resistance genes, which makes them potential probiotics, so highly demanded nowadays. Analysis of the genomes related to halophilic proteobacteria revealed that they are not involved in milk fermentation; however, the search for "useful" genes responsible for the synthesis of beneficial products/metabolites was partially positive. In addition, it has been shown that some halophiles may be involved in the synthesis of inappropriate bioactive components. The results obtained by culture-independent analyses confirm the importance of using such techniques both to clarify the quality and health-promoting properties of the product, and to look for probiotic strains with specified unique properties. This study has shown that traditional dairy foods may be a source of such beneficial strains. [ABSTRACT FROM AUTHOR]

Citrus fruits are vulnerable to green mold (caused by Penicillium digitatum) and blue mold (caused by Penicillium italicum) during storage, posing significant challenges to the industry. Therefore, biological control utilizing antagonistic bacteria has emerged as a dependable strategy for managing postharvest diseases. In this study, halophilic bacterial isolates were carefully selected from diverse saline ecosystems, including the Dead Sea, the Agadir Sea, the Rabat Sea, saline soil, and water of the Amassine Oued in Taounate, based on rigorous in vitro and in vivo antagonism bioassays. Out of 21 bacteria from different saline environments, 10 were chosen for further characterization based on the 16S rDNA gene. Notably, the EAM1 isolate demonstrated exceptional inhibitory effects, reaching a 90% inhibition rate against P. digitatum, while the ER2 isolate closely followed with an 89% inhibition rate against P. italicum. Furthermore, in bacterial supernatant experiments, six bacterial isolates effectively curbed the growth of P. digitatum, and three demonstrated efficacy against P. italicum development. In an in vivo trial spanning ten days of incubation, three highly effective isolates against P. digitatum displayed zero severity, and two of these isolates also demonstrated zero severity against P. italicum. Interestingly, a comparison of bacterial filtrates revealed that all isolates exhibited a severity level of over 50% against the pathogen causing green rot (P. digitatum), while the severity was lower than 50% for the supernatants of the two isolates used against P. italicum. In conclusion, this study highlights the promising role of halophilic bacteria, specifically Bacillus amyloliquefaciens EAM1 and B. amyloliquefaciens ER2, in controlling postharvest fruit pathogens. The findings shed light on the potential of utilizing these bioprotective agents to address the challenges posed by green and blue citrus molds, providing valuable insights for the citrus industry. [ABSTRACT FROM AUTHOR]

Soil salinization is negatively affecting soils globally, and the spread of this problem is of great concern due to the loss of functions and benefits offered by the soil resource. In the present study, we explored the diversity of halophilic and halotolerant microorganisms in the arable fraction of a sodic–saline soil without agricultural practices and two soils with agricultural practices (one sodic and one saline) near the geothermal area “Los Negritos” in Villamar, Michoacán state. This was achieved through their isolation and molecular identification, as well as the characterization of their potential for the production of metabolites and enzymes of biotechnological interest under saline conditions. Using culture-dependent techniques, 62 halotolerant and moderately halophilic strains belonging to the genera Bacillus, Brachybacterium, Gracilibacillus, Halobacillus, Halomonas, Kocuria, Marinococcus, Nesterenkonia, Oceanobacillus, Planococcus, Priestia, Salibactetium, Salimicrobium, Salinicoccus, Staphylococcus, Terribacillus, and Virgibacillus were isolated. The different strains synthesized hydrolytic enzymes under 15% (w/v) of salts, as well as metabolites with plant-growth-promoting (PGP) characteristics, such as indole acetic acid (IAA), under saline conditions. Furthermore, the production of biopolymers was detected among the strains; members of Bacillus, Halomonas, Staphylococcus, and Salinicoccus showed extracellular polymeric substance (EPS) production, and the strain Halomonas sp. LNSP3E3-1.2 produced polyhydroxybutyrate (PHB) under 10% (w/v) of total salts.

Introduction: This study aimed to identify and characterize novel siderophoreproducing organisms capable of secreting high quantities of the iron-binding compounds. In the course of this, two not yet reported halophilic strains designated ATCHAT and ATCH28T were isolated from hypersaline, alkaline surface waters of Salar de Llamará and Laguna Lejía, respectively. The alkaline environment limits iron bioavailability, suggesting that native organisms produce abundant siderophores to sequester iron. Methods: Both strains were characterized by polyphasic approach. Comparative analysis of the 16S rRNA gene sequences revealed their affiliation with the genus Halomonas. ATCHAT showed close similarity to Halomonas salicampi and Halomonas vilamensis, while ATCH28T was related closest to Halomonas ventosae and Halomonas salina. The ability of both strains to secrete siderophores was initially assessed using the chromeazurol S (CAS) liquid assay and subsequently further investigated through genomic analysis and NMR. Furthermore, the effect of various media components on the siderophore secretion by strain ATCH28T was explored. Results: The CAS assay confirmed the ability of both strains to produce iron-binding compounds. Genomic analysis of strain ATCHAT revealed the presence of a not yet reported NRPS-dependant gene cluster responsible for the secretion of siderophore. However, as only small amounts of siderophore were secreted, further investigations did not lie within the scope of this study. Via NMR and genomic analysis, strain ATCH28T has been determined to produce desferrioxamine E (DFOE). Although this siderophore is common in various terrestrial microorganisms, it has not yet been reported to occur within Halomonas, making strain ATCH28T the first member of the genus to produce a non-amphiphilic siderophore. By means of media optimization, the produced quantity of DFOE could be increased to more than 1000 µM. Discussion: Phenotypic and genotypic characteristics clearly differentiated both strains from other members of the genus Halomonas. Average nucleotide identity (ANI) values and DNA-DNA relatedness indicated that the strains represented two novel species. Therefore, both species should be added as new representatives of the genus Halomonas, for which the designations Halomonas llamarensis sp. nov. (type strain ATCHAT = DSM 114476 = LMG 32709) and Halomonas gemina sp. nov. (type strain ATCH28T = DSM 114418 = LMG 32708) are proposed. [ABSTRACT FROM AUTHOR]

The global production of fossil-based plastics has reached critical levels, and their substitution with bio-based polymers is an urgent requirement. Poly(3-hydroxybutyrate) (PHB) is a biopolymer that can be produced via microbial cultivation, but efficient microorganisms and low-cost substrates are required. Halomonas boliviensis LC1, a moderately halophilic bacterium, is an effective PHB producer, and hydrolysates of the residual stalks of quinoa (Chenopodium quinoa Willd.) can be considered a cheap source of sugars for microbial fermentation processes in quinoa-producing countries. In this study, H. boliviensis LC1 was adapted to a cellulosic hydrolysate of quinoa stalks obtained via acid-catalyzed hydrothermal pretreatment and enzymatic saccharification. The adapted strain was cultivated in hydrolysates and synthetic media, each of them with two different initial concentrations of glucose. Cell growth, glucose consumption, and PHB formation during cultivation were assessed. The cultivation results showed an initial lag in microbial growth and glucose consumption in the quinoa hydrolysates compared to cultivation in synthetic medium, but after 33 h, the values were comparable for all media. Cultivation in hydrolysates with an initial glucose concentration of 15 g/L resulted in a higher glucose consumption rate (0.15 g/(L h) vs. 0.14 g/(L h)) and volumetric productivity of PHB (14.02 mg/(L h) vs. 10.89 mg/(L h)) than cultivation in hydrolysates with 20 g/L as the initial glucose concentration. During most of the cultivation time, the PHB yield on initial glucose was higher for cultivation in synthetic medium than in hydrolysates. The produced PHBs were characterized using advanced analytical techniques, such as high-performance size-exclusion chromatography (HPSEC), Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). HPSEC revealed that the molecular weight of PHB produced in the cellulosic hydrolysate was lower than that of PHB produced in synthetic medium. TGA showed higher thermal stability for PHB produced in synthetic medium than for that produced in the hydrolysate. The results of the other characterization techniques displayed comparable features for both PHB samples. The presented results show the feasibility of producing PHB from quinoa stalks with H. boliviensis. [ABSTRACT FROM AUTHOR]

Halotolerant plant growth promoting rhizobacteria (PGPR) are beneficial microorganisms utilized to mitigate the biotic and abiotic stresses in plants. The areas of Sundarban mangroves of West Bengal, India have been reported to be rich in halotolerant microflora, yet major area remains unexplored. The present study, therefore, aims to map down the region-specific native microbial community potent of salt tolerance, plant growth promoting (PGP) activity and antagonistic activity against fungal pathogens. Bacterial samples were isolated from the saline soil of the Sundarban mangroves. A total of 156 bacterial samples were isolated and 20 were screened for their salt tolerance potential. These isolates were characterised using morphological, biochemical, and molecular approaches. Based on 16s rRNA sequencing, they were classified into 4 different genera, including Arthrobacter sp. (01 isolate), Pseudomonas plecoglossicida (01 isolate), Kocuria rosea (01 isolate), and Bacillus (17 isolates). The halotolerant isolates which possessed plant growth promoting traits including phosphate, and zinc solubilization, indole acetic acid production, siderophore, and ammonia generation were selected. Further, the effect of two halotolerant isolates GN-5 and JR-12 which showed most prominent PGP activities was evaluated in pea plant under high salinity conditions. The isolates improved survival by promoting germination (36 to 43%) and root-shoot growth and weight of pea plant in comparison to non-inoculated control plants. In a subsequent dual culture confrontation experiment, both these halo-tolerant isolates showed antagonistic activities against the aggressive root rot diseasecausing Macrophomina phaseolina (Tassi) Goid NAIMCC-F-02902. The identified isolates could be used as potential bioagents for saline soils, with potential antagonistic effect on root rot disease. However, further studies at the physiological and molecular level would help to delineate a detail mechanistic understanding of broad-spectrum defence against salinity and potential biotic pathogen. [ABSTRACT FROM AUTHOR]

This article provides the first description of the bacterial diversity in the Permian rock of the Upper Pechora salt basin. Halophilic and halotolerant bacteria of the classes Gammaproteobacteria (from the genera Halomonas, Marinobacter, and Idiomarina) and Actinomycetia (from the genus Dietzia) were isolated from the brines extracted during the underground dissolution of carnallite rocks in the pilot well of the Yakshinskoe deposit (Komi Republic, Russia) of potassium-magnesium salts. The analysis of 16S rRNA gene sequences cloned from the total DNA of the floatable part of the insoluble brine residues revealed the following bacterial classes: Gammaproteobacteria (closely related to the genera Idiomarina, Marinimicrobium, Marinobacter, Methylophaga, and Pseudidiomarina), Betaproteobacteria (phenologically similar to the genera Achromobacter and Methylotenera), as well as Alphaproteobacteria and Flavobacteriia (related to the genera Sulfitobacter and Salegentibacter, respectively). Several identified phylotypes (clones 113YS, 8YS, 150YS, and 157YS) had a low level of similarity with the closest type strains of the genera Methylophaga (M. nitratireducenticrescens JAM1T, 96.86%), Salegentibacter (S. salarius ISL-6T, 98.58%), and Methylotenera (M. versatilis 301T, 98.05% and 98.19%). This indicates that the brine samples contained new, previously undescribed, bacterial taxa. The results obtained define and shape the future prospects for studying the phylogenetic and functional diversity of microorganisms in the salt strata of the Yakshinskoe deposit.

The sunflower (Helianthus annus L.) is a vital oilseed crop exposed to drought globally. A vast proportion of research is devoted to the naturally occurring microbes and their interaction with plants to alleviate stress consequences. Halophilic bacterial strains, i.e., Bacillus cereus KUB-15 (accession number NR 074540.1), KUB-27 (accession number NR 074540.1), and Bacillus licheniformis strain AAB9 (accession number MW362506), were isolated. Later, isolated strains were used for sunflower through inoculation. Plants were allowed to grow, and thirty-days-old plants were exposed to fixed moisture stress (40–45%). The functionality of photosystem II, light-harvesting ability, and physiological tolerance of cultivars were examined. Bacterial strains B. licheniformis sustained substantial electron flow in between photosystem II (PS II) and photosystem I (PS 1) that not only favored the passable photosynthetic performance but also enhanced antioxidant enzyme activity under stress condition. Compared to other halophilic strains, Bacillus licheniformis did manage reasonable relative water content (RWC), chlorophyll content index (CCI) and biomass production under stress condition. In comparison to both sunflower cultivars, bacterial inoculation was greatly restored growth and photosynthetic performance in Agsun-5264 than S-278 under moisture stress environment. Hence, it is suggested that that bacterial strain and plants cultivar compatibility are essential aspect for sustainable agriculture production. [Display omitted] • Halophilic soil bacteria sustained quantum harvesting and energy flow. • Bacterial strains improved the oxygen-evolving complex activity. • PS II functionality and physiological tolerance are concurrent. [ABSTRACT FROM AUTHOR]

Aims: The present study was aimed to determine the diversity of the halophilic and halotolerant bacteria with hydrolase activities from salterns of the protected ecosystem Khnifiss lagoon (Morocco). Methodology and results: Bacteria were isolated from sediment samples collected at five hypersaline sites on three different growth media supplemented with various concentrations of NaCl. Thirty bacterial isolates were identified using the 16S rDNA sequencing method. Physiological characterization was examined on Columbia agar with different concentrations of NaCl and pH values and incubated at different temperatures. Enzymatic activities were tested in submerged cultures with appropriate substrates. A total of 246 halophilic bacterial isolates from the salines of the protected ecosystem of Khnifiss lagoon in the south of Morocco were able to produce different hydrolases (cellulases, amylases, DNases, lipases and proteases). Furthermore, the majority of the isolates were classified as moderately halophilic bacteria that grew optimally between 5% and 15% of NaCl, and they adapted to other extreme conditions than salt: some cases tolerated a pH range of 4.5 to 9.4, as well as a temperature range of 10 to 50 °C. The 16S rDNA sequencing and phylogenetic analysis results indicated that most of the bacteria isolated from the salt marshes studied belong to the genus Bacillus. Conclusion, significance and impact of study: Phenotypic and phylogenetic characterization of halophilic and halotolerant bacteria isolated from the salines of the protected ecosystem of Khnifiss lagoon has shown great diversity. Screening of hydrolytic enzymes produced by these bacteria suggests that the salines of the Khnifiss lagoon are a rich source of technologically interesting bacteria. [ABSTRACT FROM AUTHOR]

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IntroductionThis study aimed to identify and characterize novel siderophore-producing organisms capable of secreting high quantities of the iron-binding compounds. In the course of this, two not yet reported halophilic strains designated ATCHAT and ATCH28T were isolated from hypersaline, alkaline surface waters of Salar de Llamará and Laguna Lejía, respectively. The alkaline environment limits iron bioavailability, suggesting that native organisms produce abundant siderophores to sequester iron.MethodsBoth strains were characterized by polyphasic approach. Comparative analysis of the 16S rRNA gene sequences revealed their affiliation with the genus Halomonas. ATCHAT showed close similarity to Halomonas salicampi and Halomonas vilamensis, while ATCH28T was related closest to Halomonas ventosae and Halomonas salina. The ability of both strains to secrete siderophores was initially assessed using the chromeazurol S (CAS) liquid assay and subsequently further investigated through genomic analysis and NMR. Furthermore, the effect of various media components on the siderophore secretion by strain ATCH28T was explored.ResultsThe CAS assay confirmed the ability of both strains to produce iron-binding compounds. Genomic analysis of strain ATCHAT revealed the presence of a not yet reported NRPS-dependant gene cluster responsible for the secretion of siderophore. However, as only small amounts of siderophore were secreted, further investigations did not lie within the scope of this study. Via NMR and genomic analysis, strain ATCH28T has been determined to produce desferrioxamine E (DFOE). Although this siderophore is common in various terrestrial microorganisms, it has not yet been reported to occur within Halomonas, making strain ATCH28T the first member of the genus to produce a non-amphiphilic siderophore. By means of media optimization, the produced quantity of DFOE could be increased to more than 1000 µM.DiscussionPhenotypic and genotypic characteristics clearly differentiated both strains from other members of the genus Halomonas. Average nucleotide identity (ANI) values and DNA–DNA relatedness indicated that the strains represented two novel species. Therefore, both species should be added as new representatives of the genus Halomonas, for which the designations Halomonas llamarensis sp. nov. (type strain ATCHAT = DSM 114476 = LMG 32709) and Halomonas gemina sp. nov. (type strain ATCH28T = DSM 114418 = LMG 32708) are proposed.

The salinization of soils is a growing agricultural concern worldwide. Irrigation practices, drought, and climate change are leading to elevated salinity levels in many regions, resulting in reduced crop yields. However, there is potential for a solution in the microbiome of halophytes, which are naturally salt-tolerant plants. These plants harbor a salt-tolerant microbiome in their rhizosphere (around roots) and endosphere (within plant tissue). These bacteria may play a significant role in conferring salt tolerance to the host plants. This leads to the possibility of transferring these beneficial bacteria, known as salt-tolerant plant-growth-promoting bacteria (ST-PGPB), to salt-sensitive plants, enabling them to grow in salt-affected areas to improve crop productivity. In this review, the background of salt-tolerant microbiomes is discussed and their potential use as ST-PGPB inocula is explored. We focus on two Gram-negative bacterial genera, Halomonas and Kushneria, which are commonly found in highly saline environments. These genera have been found to be associated with some halophytes, suggesting their potential for facilitating ST-PGPB activity. The study of salt-tolerant microbiomes and their use as PGPB holds promise for addressing the challenges posed by soil salinity in the context of efforts to improve crop growth in salt-affected areas.

Pigments producing strains Halobacillus yeomjeoni(81-1) Salinicoccus sp. (82-1) Bacillus infantis (63-11) Bacillus amyloliquefaciens (60-5) and Staphylococcus carnosus (48-10) were isolated from salty fermented foods. As per FTIR analysis, IR spectrum of pigment from each isolate were similar to IR spectrum of xanthophyll as previously reported. This study concluded that the pigments generated from these different halophilic strains with different color shade were all derivatives of carotenoid. Dominant bacterial pigments of these strains analyzed by High-Performance Liquid Chromatography (HPLC) compared to standard reagent included lycopene, lutein and β-carotene. Antimicrobial assays of crude pigment extract of 81-1 isolate exhibited highest inhibitory effect on Staphylococcus aureus, while 82-1 and 60-5 isolates best inhibited Escherichia coli and Bacillus cereus, respectively. DPPH assay of 60-5 isolate demonstrated significantly higher antioxidant activity as compared to others crude pigments. Furthermore, virulence analysis of strains depicted no key biogenic amine genes and no hemolytic activity in any of the isolates.

The halophilic consortia were enriched from water samples of Abhor, Red Sea, Jeddah, Saudi Arabia for the degradation of phenanthrene, fluorene, hexadecane, pyrene, and treatment of automobile service station wastewater under saline conditions (4%). Complete degradation of phenanthrene and fluorene was recorded up to a concentration of 500 mg.L-1 in 12 days, when the concentration was raised to 800 mg.L-1, the percentage of degradation of the two compounds was recorded by 84 and 90% within 14 days, while when the concentration increased to 1000 mg.L-1, a significant decline was recorded. Pyrene degradation was studied under saline conditions, where it recorded a degradation rate of 92 and 81% at a concentration of 50 and 100 mg.L-1 in 10 and 12 days, respectively, while when increasing the concentration, a severe decrease in the percentage of degradation was recorded that reached 57 and 44% at concentration 200 and 300 mg.L-1, respectively .Hexadecane recorded complete degradation at a concentration of 0.5 and 1%, within 4 and 6 days, respectively, while at a concentration of 1.5%, the rate of deterioration was 88% in 10 days. Record 93% removal of COD in CSTR within 40th day, when treatment of automobile service station wastewater with halophilic bacterial consortia. The existing bacterial strains were classified as potentially responsible for petroleum hydrocarbon degradation and treatment of automobile service station wastewater such as Ochrobactrum, Propionispira, Martelella, Bacillus, Marinobacter, and Azospira. The present study recommends that the hydrophilic consortia can be used in the treatment of automobile service station wastewater under saline conditions. [ABSTRACT FROM AUTHOR]

Marine microorganisms have evolved a large variety of metabolites and biochemical processes, providing great opportunities for biotechnologies. In the search for new hydrolytic enzymes and antimicrobial compounds with enhanced characteristics, the current study explored the diversity of cultured and uncultured marine bacteria in Black Sea water from two locations along the Romanian coastline. Microbial cell density in the investigated samples varied between 65 and 12.7 × 103 CFU·mL−1. The total bacterial community identified by Illumina sequencing of 16S rRNA gene comprised 185 genera belonging to 46 classes, mainly Gammaproteobacteria, Alphaproteobacteria, Flavobacteriia, and 24 phyla. The 66 bacterial strains isolated on seawater-based culture media belonged to 33 genera and showed variable growth temperatures, growth rates, and salt tolerance. A great fraction of these strains, including Pseudoalteromonas and Flavobacterium species, produced extracellular proteases, lipases, and carbohydrases, while two strains belonging to the genera Aquimarina and Streptomyces exhibited antimicrobial activity against human pathogenic bacteria. This study led to a broader view on the diversity of microbial communities in the Black Sea, and provided new marine strains with hydrolytic and antimicrobial capabilities that may be exploited in industrial and pharmaceutical applications. [ABSTRACT FROM AUTHOR]

Abstract Background The genus Planococcus is comprised of halophilic bacteria generally reported for the production of carotenoid pigments and biosurfactants. In previous work, we showed that the culturing of the orange-pigmented Planococcus sp. CP5-4 isolate increased the evaporation rate of industrial wastewater brine effluent, which we attributed to the orange pigment. This demonstrated the potential application of this bacterium for industrial brine effluent management in evaporation ponds for inland desalination plants. Here we identified a C30-carotenoid biosynthetic gene cluster responsible for pigment biosynthesis in Planococcus sp. CP5-4 through isolation of mutants and genome sequencing. We further compare the core genes of the carotenoid biosynthetic gene clusters identified from different Planococcus species’ genomes which grouped into gene cluster families containing BGCs linked to different carotenoid product chemotypes. Lastly, LC–MS analysis of saponified and unsaponified pigment extracts obtained from cultures of Planococcus sp. CP5-4, revealed the structure of the main (predominant) glucosylated C30-carotenoid fatty acid ester produced by Planococcus sp. CP5-4. Results Genome sequence comparisons of isolated mutant strains of Planococcus sp. CP5-4 showed deletions of 146 Kb and 3 Kb for the non-pigmented and “yellow” mutants respectively. Eight candidate genes, likely responsible for C30-carotenoid biosynthesis, were identified on the wild-type genome region corresponding to the deleted segment in the non-pigmented mutant. Six of the eight candidate genes formed a biosynthetic gene cluster. A truncation of crtP was responsible for the “yellow” mutant phenotype. Genome annotation revealed that the genes encoded 4,4′-diapolycopene oxygenase (CrtNb), 4,4′- diapolycopen-4-al dehydrogenase (CrtNc), 4,4′-diapophytoene desaturase (CrtN), 4,4′- diaponeurosporene oxygenase (CrtP), glycerol acyltransferase (Agpat), family 2 glucosyl transferase 2 (Gtf2), phytoene/squalene synthase (CrtM), and cytochrome P450 hydroxylase enzymes. Carotenoid analysis showed that a glucosylated C30-carotenoid fatty acid ester, methyl 5-(6-C17:3)-glucosyl-5, 6′-dihydro-apo-4, 4′-lycopenoate was the main carotenoid compound produced by Planococcus sp. CP5-4. Conclusion We identified and characterized the carotenoid biosynthetic gene cluster and the C30-carotenoid compound produced by Planococcus sp. CP5-4. Mass-spectrometry guided analysis of the saponified and unsaponified pigment extracts showed that methyl 5-glucosyl-5, 6-dihydro-apo-4, 4′-lycopenoate esterified to heptadecatrienoic acid (C17:3). Furthermore, through phylogenetic analysis of the core carotenoid BGCs of Planococcus species we show that various C30-carotenoid product chemotypes, apart from methyl 5-glucosyl-5, 6-dihydro-apo-4, 4′-lycopenoate and 5-glucosyl-4, 4-diaponeurosporen-4′-ol-4-oic acid, may be produced that could offer opportunities for a variety of applications.

Research background. Haloalkaline proteases are one of the most interesting types of commercial enzymes in various industries due to their high specific activity and stability under extreme conditions. Biochemical characterization of enzymes is an important requirement for determining their potential for application in industrial fields. Most of microbial proteases have been isolated from Bacillus spp. In this study, the purification and characterization of an extracellular haloprotease produced from Bacillus sp. KB111 strain, which was previously isolated from mangrove forest sediments, are investigated for industrial applications. Experimental approach. The whole genome of KB111 strain was identified by DNA sequencing. Its produced protease was purified by salting out and anion-exchange chromatography, characterized based on protease activity and stability using a peptide substrate, and identified by LC-MS/MS. Results and conclusions. The strain KB111 was identified as Bacillus licheniformis. The molecular mass of its extracellular protease, termed KB-SP, was estimated to be 70 kDa. The optimal pH and temperature for the activity of this protease were 7 and 50 °C, respectively, while the enzyme exhibited maximal activity in the broad salinity range of 2–4 M NaCl. It was fully stable at an alkaline pH range of 7–11 at 50 °C with a half-life of 90 min. Metal ions such as K+, Ca2+ and Mg2+ could enhance the enzyme activity. Therefore, this protease indicates a high potential for the applications in the food and feed industry, as well as the waste management since it can hydrolyse protein at high alkaline pH and salt concentrations. The amino acid profiles of the purified KB-SP determined by LC-MS/MS analysis showed high score matching with the peptidase S8 of B. licheniformis LMG 17339, corresponding to the mature domain of a minor extracellular protease (Vpr). Amino acid sequence alignment and 3D structure modelling of KB-SP showed a conserved catalytic domain, a protease-associated (PA) domain and a C-terminal domain. Novelty and scientific contribution. A novel extracellular haloprotease from B. licheniformis was purified, characterized and identified. The purified protease was identified as being a minor extracellular protease (Vpr) and this is the first report on the halotolerance of Vpr. This protease has the ability to work in harsh conditions, with a broad alkaline pH and salinity range. Therefore, it can be useful in various applications in industrial fields.

Abstract Background Halophiles are an excellent source of enzymes that are not only salt stable, but also can withstand and carry out reaction efficiently under extreme conditions. l-glutaminase has attracted much attention with respect to proposed applications in several fields such as pharmaceuticals and food industries. The aim of the present study was to investigate the anticancer activity of l-glutaminase produced by halophilic bacteria. Various halophilic bacterial strains were screened for extracellular l-glutaminase production. An attempt was made to study the optimization, purification, and characterization of l-glutaminase from Bacillus sp. DV2-37. The antitumor activity of the produced enzyme was also investigated. Results The potentiality of 15 halophilic bacterial strains isolated from the marine environment that produced extracellular l-glutaminase was investigated. Bacillus sp. DV2-37 was selected as the most potent strain and optimized for enzyme production. The optimization of fermentation process revealed that the highest enzyme activity (47.12 U/ml) was observed in a medium supplemented with 1% (w/v) glucose as a carbon source, 1% (w/v) peptone as a nitrogen source, 5% (w/v) NaCl, the initial pH was 7.0, at 37 °C, using 20% (v/v) inoculum size after 96 h of incubation. The produced crude enzyme was partially purified by ammonium sulfate precipitation and dialysis. Of the various parameters tested, pH 7, 40 °C, and 5% NaCl were found to be the best for l-glutaminase activity. The enzyme also exhibited high salt and temperature stability. The antitumor effect against human breast (MCF-7), hepatocellular (HepG-2), and colon (HCT-116) carcinoma cell lines revealed that l-glutaminase produced by Bacillus sp. DV2-37 showed potent cytotoxic activity of all the tested cell lines in a dose-dependent manner with an IC50 value of 3.5, 3.4, and 3.8 µg/ml, respectively. Conclusions The present study proved that l-glutaminase produced by marine bacteria holds proper features and it has a high potential to be useful for many therapeutic applications.

Biofilm-forming microbes can pose a major health risk that is difficult to combat. Nanotechnology, on the other hand, represents a novel technique for combating and eliminating biofilm-forming microbes. In this study, the selenium nanoparticles (SeNPs) were biosynthesized from moderate halophilic bacteria isolated from Pichavaram mangrove sediments. The bacterial strain S8 was found to be efficient for SeNPs synthesis and hence identified by 16s r RNA sequencing as Shewanella sp. In UV- spectral analysis the SeNPs displayed a peak at 320 nm due to surface plasmon resonance (SPR). The cell-free extract of Shewanella sp. and SeNPs indicates that the various functional groups in the cell-free extract were mainly involved in the synthesis and stabilization of SeNPs. The SeNPs had a spherical form with average diameter of 49 ± 0.01 nm, according to the FESEM analysis. The EDX shows the distinctive peaks of selenium at 1.37, 11.22.12.49 Kev. In the agar well diffusion method, the SeNPs show inhibitory activity against all the test pathogens with the highest activity noted against P. aeruginosa with a zone of inhibition of 22.7 ± 0.3 mm. The minimal inhibitory concentration (MIC) value of 80 μg/ml, minimal bactericidal concentration (MBC) of 160 μg/ml, and susceptibility constant of 0.043 μg/ml show that SeNPs highly effective against P. aeruginosa. The Sub-MIC value of SeNPs of 20 μg/ml was found to inhibit P. aeruginosa biofilm by 85% as compared to the control. Further, the anti-virulence properties viz., pyocyanin, pyoverdine, hemolytic, and protease inhibition revealed the synthesized SeNPs from halophilic bacteria control the pathogenicity of P. aeruginosa. • Selenium nanoparticles (SeNPs) synthesized from halophilic bacteria, Shewanella sp. The SeNPs was characterized by spherical shape, 49 ± 0.01 nm diameter, with surface plasmon resonance at 320 nm. • SeNPs inhibited various pathogens, notably Pseudomonas aeruginosa , with a 22.7 ± 0.3 mm zone of inhibition, MIC of 80 μg/ml, MBC of 160 μg/ml, and susceptibility constant of 0.043 μg/ml. • SeNPs at sub-MIC (20 μg/ml) inhibited P. aeruginosa biofilm formation by 85%. • SeNPs exhibited anti-virulence properties, including pyocyanin, pyoverdine, hemolysis, and protease inhibition. • Demonstrates potential of SeNPs from halophilic bacteria in combating biofilm-forming microbes and controlling virulence of P. aeruginosa. [ABSTRACT FROM AUTHOR]

Citrus fruits are vulnerable to green mold (caused by Penicillium digitatum) and blue mold (caused by Penicillium italicum) during storage, posing significant challenges to the industry. Therefore, biological control utilizing antagonistic bacteria has emerged as a dependable strategy for managing postharvest diseases. In this study, halophilic bacterial isolates were carefully selected from diverse saline ecosystems, including the Dead Sea, the Agadir Sea, the Rabat Sea, saline soil, and water of the Amassine Oued in Taounate, based on rigorous in vitro and in vivo antagonism bioassays. Out of 21 bacteria from different saline environments, 10 were chosen for further characterization based on the 16S rDNA gene. Notably, the EAM1 isolate demonstrated exceptional inhibitory effects, reaching a 90% inhibition rate against P. digitatum, while the ER2 isolate closely followed with an 89% inhibition rate against P. italicum. Furthermore, in bacterial supernatant experiments, six bacterial isolates effectively curbed the growth of P. digitatum, and three demonstrated efficacy against P. italicum development. In an in vivo trial spanning ten days of incubation, three highly effective isolates against P. digitatum displayed zero severity, and two of these isolates also demonstrated zero severity against P. italicum. Interestingly, a comparison of bacterial filtrates revealed that all isolates exhibited a severity level of over 50% against the pathogen causing green rot (P. digitatum), while the severity was lower than 50% for the supernatants of the two isolates used against P. italicum. In conclusion, this study highlights the promising role of halophilic bacteria, specifically Bacillus amyloliquefaciens EAM1 and B. amyloliquefaciens ER2, in controlling postharvest fruit pathogens. The findings shed light on the potential of utilizing these bioprotective agents to address the challenges posed by green and blue citrus molds, providing valuable insights for the citrus industry.

In this study, we used culture-independent analysis based on 16S rRNA gene amplicons and metagenomics to explore in depth the microbial communities and their metabolic capabilities of artisanal brine cheeses made in the North Caucasus. Additionally, analysis of organic acid profiles was carried out for cheese characterization. Twelve cheese samples (designated as 05SR–16SR) from various artisanal producers were taken from five different villages located in Northern Ossetia–Alania (Russia). These cheeses were made using methods based on cultural traditions inherited from previous generations and prepared using a relatively uncontrolled fermentation process. The microbial diversity of Caucasus artisanal cheeses was studied for the first time. The results showed a diverse composition in all cheeses, with Bacillota (synonym Firmicutes) (9.1–99.3%) or Pseudomonadota (synonym Proteobacteria) (0.2–89.2%) prevalence. The microbial communities of the majority of the studied cheeses were dominated by lactic acid bacteria (LAB) genera, like Lactococcus (10.3–77.1% in 07SR, 09SR, 10SR, 11SR, 13SR, 15SR, 16SR), Lactobacillus (54.6% in 09SR), Streptococcus (13.9–93.9% in 11SR, 13SR, 14SR, 15SR), Lactiplantibacillus (13.4–30.6% in 16SR and 07SR) and Lentilactobacillus (5.9–14.2% in 09SR, 10SR and 13SR). Halophilic lactic acid bacteria belonging to the Tetragenococcus genus accounted for 7.9–18.6% in 05SR and 06SR microbiomes. A distinctive feature of Ossetia cheese microbiomes was the large variety of halophilic proteobacteria, and in some cheeses they prevailed, e.g., Chromohalobacter (63–76.5% in 05SR and 06SR), Psychrobacter (10–47.1% in 08SR, 11SR, 12SR), Halomonas (2.9–33.5% in 06SR, 08SR, 11SR and 12SR), Marinobacter (41.9% in 12SR) or Idiomarina (2.9–14.4% in 06SR, 08SR and 11SR samples). Analysis of the genomes assembled from metagenomes of three cheeses with different bacterial composition revealed the presence of genes encoding a variety of enzymes, involved in milk sugar, proteins and lipid metabolism in genomes affiliated with LAB, as well as genes responsible for beneficial bioamine and bacteriocin synthesis. Also, most of the LAB did not contain antibiotic resistance genes, which makes them potential probiotics, so highly demanded nowadays. Analysis of the genomes related to halophilic proteobacteria revealed that they are not involved in milk fermentation; however, the search for “useful” genes responsible for the synthesis of beneficial products/metabolites was partially positive. In addition, it has been shown that some halophiles may be involved in the synthesis of inappropriate bioactive components. The results obtained by culture-independent analyses confirm the importance of using such techniques both to clarify the quality and health-promoting properties of the product, and to look for probiotic strains with specified unique properties. This study has shown that traditional dairy foods may be a source of such beneficial strains.

An experiment was conducted at the Indian Agricultural Research Institute, New Delhi (2017-18) to report the identification of halophilic poly-ß-hydroxybutyrate (PHB) producing bacteria and optimization of process parameters for maximum PHB recovery. The phylogenetic analysis classified the isolates into bacterial phylum α, γ-Proteobacteria, and Firmicutes. Halomonas sp. KB7 and Stenotrophomonas maltophila B11 produced maximum PHB in mineral salt media having optimized C and N concentration with 10% NaCl. Optimizing media increased PHB production from 23.80–73.7% w/w for Halomonas sp and 29.5–78.3 % w/w for S. maltophila.

The increased use of ectoine and hydroxyectoine in cosmetics and pharmaceuticals has led to the increasing demand for these bioactive compounds. This study aims to investigate the production of ectoine and hydroxyectoine by halophilic bacteria isolated from traditional solar saltern at Pejarakan Village, Buleleng Regency, Province of Bali, Indonesia. The halophilic bacteria were grown from the brine and the sediment samples using Luria Bertani media. The production of ectoine and hydroxyectoine was determined by inoculating the bacteria in MM63 media containing 12% w/v NaCl. Ectoine and hydroxyectoine were then extracted from the bacterial cells using a mixture of methanol/chloroform/water (10/5/4). Finally, the ability of the bacteria to excrete ectoine and hydroxyectoine was investigated using the osmotic downshock technique. The results showed that a total of 88 halophilic bacteria have been isolated which showed varied salt tolerances from 0 to 27.5% w/v. Most of the bacteria (86 isolates) were able to grow in MM63 media, suggesting the potential of the bacteria producing ectoine and hydroxyectoine. Further investigation showed that 33 selected halophilic bacteria were able to produce ectoine and hydroxyectoine with levels of 9.1 to 301.8 mg/L and 3.9 to 122.1 mg/L, respectively. All the bacteria were also able to excrete ectoine and hydroxyectoine after the osmotic downshock process with levels of 9.8 to 277.5 mg/L and 14.3 to 122.7 mg/L, respectively. The best ectoine and hydroxyectoineproducing bacteria showed the closest homology relationship with Salinivibrio costicola and Salinivibrio kushneri. Our study has found several promising candidates for ectoine and hydroxyectoine producers. [ABSTRACT FROM AUTHOR]

This research was done to investigate the application of halophilic bacteria in a biofloc production system to grow Artemia franciscana in the laboratory, in which part of a standard microalgae feeding regime was replaced by bioflocs. Bioflocs were produced according to a standard procedure, using rice bran and vinasse as carbon sources, a commercial probiotic product, and halophilic Bacillus sp., originating from Urmia Lake, Iran, as halophilic bacteria. Three successive laboratory culture tests were conducted at salinities 60 (experiments 1 and 3) and 120 g L−1 (experiment 2) for 21, 14 and 14 days, respectively. Five feeding regimes were examined; the control treatment feeding a standard regime of only the microalga Dunaliella tertiolecta, and four biofloc treatments: 90% and 75% replacement of microalgae by bioflocs, both without and with halophilic addition. Depending on the experiment, Artemia performance was assessed as growth, reproductive performance, fatty acid and proximate composition and/or digestive enzyme activity. Applying halophilic bacteria in biofloc systems had no significant effect on the measured parameters. We further conclude that Artemia franciscana can be cultured successfully using bioflocs as the main food source, with limited microalgae supplementation (10%–25%) with no significant effect on survival, length, proximate composition and levels of most fatty acids in Artemia biomass. A number of fecundity parameters were negatively affected by 75% substitution of microalgae by bioflocs. This research opens interesting perspectives to produce Artemia at a bigger scale, e.g., in tanks or pond conditions, where production of sufficient quantities of suitable microalgae species might be problematic. [ABSTRACT FROM AUTHOR]

The salinization of soil is responsible for the reduction in the growth and development of plants. As the global population increases day by day, there is a decrease in the cultivation of farmland due to the salinization of soil, which threatens food security. Salt-affected soils occur all over the world, especially in arid and semi-arid regions. The total area of global salt-affected soil is 1 billion ha, and in India, an area of nearly 6.74 million ha−1 is salt-stressed, out of which 2.95 million ha−1 are saline soil (including coastal) and 3.78 million ha−1 are alkali soil. The rectification and management of salt-stressed soils require specific approaches for sustainable crop production. Remediating salt-affected soil by chemical, physical and biological methods with available resources is recommended for agricultural purposes. Bioremediation is an eco-friendly approach compared to chemical and physical methods. The role of microorganisms has been documented by many workers for the bioremediation of such problematic soils. Halophilic Bacteria, Arbuscular mycorrhizal fungi, Cyanobacteria, plant growth-promoting rhizobacteria and microbial inoculation have been found to be effective for plant growth promotion under salt-stress conditions. The microbial mediated approaches can be adopted for the mitigation of salt-affected soil and help increase crop productivity. A microbial product consisting of beneficial halophiles maintains and enhances the soil health and the yield of the crop in salt-affected soil. This review will focus on the remediation of salt-affected soil by using microorganisms and their mechanisms in the soil and interaction with the plants. [ABSTRACT FROM AUTHOR]

Halophiles are excellent sources of enzymes which are not only salt stable but also perform catalysis under extreme reaction conditions. The habitat of salt mines and its microbial diversity have not been thoroughly explored. In the present study, seven halophilic inulinase-producing bacteria (H1N1–H1N7) were isolated from the Bahadarkhel salt mines of Pakistan, and were identified based on their morphological, biochemical and molecular features. The strains H1N3, H1N4, H1N6, H1N7 were capable of growing at 20% salt concentration and therefore were considered as extremely halotolerant. Inulinase activities of the isolates were detected in inulin-containing broth media, and were further confirmed on inulin-based agar plates. The strains HIN1, H1N3, H1N5, and H1N7 exhibited the maximum zone of clearance (≥15 mm) on inuline agar medium. The strain H1N1 showed the highest zone of clearance of 19 mm. Morphological, biochemical and molecular characterization showed that the inulinase producing isolates were related to Bacillus and Klebsiella genera. The molecular identification was based on 16S rRNA gene sequencing. The strain H1N2 was capable of producing the four tested halozymes including inulinase, amylase, protease, and lipase. The strains HIN3, HIN4, and H1N5 were capable of producing three halozymes, i.e., inulinase, amylase, and protease while the strains H1N6 and H1N7 produced inulinases, lipases and proteases. These salt tolerant bacterial strains exhibiting diverse enzyme characteristics and phylogeny could be highly useful for future practical applications. [ABSTRACT FROM AUTHOR]

Background The rise of infectious diseases and the emergence of resistant pathogens pose significant challenges to human health. In response to this global threat, researchers are exploring novel sources of bioactive compounds for effective antimicrobial therapies. One avenue of investigation is the study of halophilic bacteria and their secondary metabolites. These bacteria thrive under extreme conditions and produce valuable bioactive metabolites, which have the potential for therapeutic applications. Methods In this study, the potent bacterial cultures obtained from the Payanur salt pan, Tamil Nadu, were analyzed for the antimicrobial activity of their metabolites. The secondary metabolites were obtained from the halophilic bacteria by culturing the bacteria in 8% NaCl. The resultant secondary metabolites produced were extracted using ethyl acetate and their antimicrobial property was studied using the well diffusion method. The minimum inhibitory concentration (MIC) of these metabolites against five clinical pathogens, namely, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans was determined. Their antioxidant property was studied using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method and biological compatibility was determined by hemolytic assay of the secondary metabolites. Results The potent halophilic bacteria isolated from salt pan bacteria were phenotypically and genotypically identified as Halobacillus sp .  The secondary metabolites extracted from these bacteria yielded 110 mg of crude metabolites. The antimicrobial activity of crude metabolites shows a moderate zone of inhibition of 14 mm for P. aeruginosa , 13 mm for E. coli and C. albicans, and 11 mm for S. aureus . The minimum inhibitory concentration was 128 µg/mL for E. coli , P. aeruginosa, and C. albicans,  which was found to be the best growth inhibition concentration. The DPPH scavenging activity shows a higher activity till the concentration of 64 µg/mL. The hemolytic activity of 25% is obtained at 128 µg/mL and below 64 µg/mL, there is no hemolytic activity. The gas chromatography-mass spectrometry (GC-MS) analysis of the secondary metabolites shows the presence of 17 compounds. Among them, there were four major compounds: (i) cyclo(L-prolyl-L-valine) (probability of 95.63%), (ii) pyrrolo[1,2-a]pyrazine- 1,4-dione,hexahydro-3-(2-methylpropl) (probability of 94.45%), (iii) 2,5-piperazinedione,3,6-bis(2-methylpropyl) (probability of 71.94%) and (iv) pyrrolo[1,2-a]pyrazine-1,4-dione,hexahydro-3-(phenylmethyl) (probability of 88.01%). Conclusion In conclusion, the isolated bacterium is confirmed to be Halobacillus sp.   and the secondary metabolites produced by this bacterium could be the potential source for the development of novel antimicrobial and antioxidant compounds that are highly biologically compatible. Further research may help to develop novel compounds in the pharmaceutical industry., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Saleem et al.)