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A moderately halophilic bacterium isolated from the water samples collected from a salt field, Salinivibrio sp. TGB10 was found capable of producing poly-3-hydroxybutytate (PHB) from various sugars. Cell dry weight (CDW) of 8.82 g/L and PHB titer of 6.84 g/L were obtained using glucose as the carbon source after 24 h of cultivation in shake flasks. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was synthesized when propionate was provided as secondary carbon source. Salinivibrio sp. TGB10 exhibited favorable tolerance to propionate. The use of 8 g/L propionate and 20 g/L glucose as combinational substrates yielded 1.45 g/L PHBV with a 3-hydroxyvalerate monomer content of 72.02 mol% in flask cultures. In bioreactor study, CDW of 33.45 g/L and PHBV titer of 27.36 g/L were obtained after 108 h of fed-batch cultivation. The results indicated that Salinivibrio sp. TGB10 is a promising halophilic bacterium for the production of PHBV with various polymer compositions.

Proteins of halophilic organisms, which accumulate molar concentrations of KCl in their cytoplasm, have a much higher content in acidic amino acids than proteins of mesophilic organisms. It has been proposed that this excess is necessary to maintain proteins hydrated in an environment with low water activity, either via direct interactions between water and the carboxylate groups of acidic amino acids or via cooperative interactions between acidic amino acids and hydrated cations. Our simulation study of five halophilic proteins and five mesophilic counterparts does not support either possibility. The simulations use the AMBER ff14SB force field with newly optimized Lennard-Jones parameters for the interactions between carboxylate groups and potassium ions. We find that proteins with a larger fraction of acidic amino acids indeed have higher hydration levels, as measured by the concentration of water in their hydration shell and the number of water/protein hydrogen bonds. However, the hydration level of each protein is identical at low (bKCl = 0.15 mol/kg) and high (bKCl = 2 mol/kg) KCl concentrations; excess acidic amino acids are clearly not necessary to maintain proteins hydrated at high salt concentration. It has also been proposed that cooperative interactions between acidic amino acids in halophilic proteins and hydrated cations stabilize the folded protein structure and would lead to slower dynamics of the solvation shell. We find that the translational dynamics of the solvation shell is barely distinguishable between halophilic and mesophilic proteins; if such a cooperative effect exists, it does not have that entropic signature.

Every year, new organisms that survive and colonize adverse environments are discovered and isolated. Those organisms, called extremophiles, are distributed throughout the world, both in aquatic and terrestrial environments, such as sulfurous marsh waters, hydrothermal springs, deep waters, volcanos, terrestrial hot springs, marine saltern, salt lakes, among others. According to the ecosystem inhabiting, extremophiles are categorized as thermophiles, psychrophiles, halophiles, acidophiles, alkalophilic, piezophiles, saccharophiles, metallophiles and polyextremophiles. They have developed chemical adaptation strategies that allow them to maintain their cellular integrity, altering physiology or improving repair capabilities; one of them is the biosynthesis of extracellular polysaccharides (EPS), which constitute a slime and hydrated matrix that keep the cells embedded, protecting from environmental stress (desiccation, salinity, temperature, radiation). EPS have gained interest; they are explored by their unique properties such as structural complexity, biodegradability, biological activities, and biocompatibility. Here, we present a review concerning the biosynthesis, characterization, and potential EPS applications produced by extremophile microorganisms, namely, thermophiles, halophiles, and psychrophiles. A bibliometric analysis was conducted, considering research articles published within the last two decades. Besides, an overview of the culture conditions used for extremophiles, the main properties and multiple potential applications of their EPS is also presented.

This study aims to screening of protease producing bacterial strain from saltpan located in Kanyakumari. Proteolytic bacterial strains were isolated by using skim milk agar plates. The potent bacterial isolate (SP II-4) was typically identified as Bacillus sp. SP II-4 by studying phenotypic characteristics. The purified enzyme fraction showed 591.04 (U/mg) of specific activity. The protease enzyme liberated from this strain illustrated better stability and activity in pH 10.0, 40 °C and stable upto 7.5% salt. The protease enzyme demonstrated better content lens cleansing effectiveness along with common chemical disinfectant. These above properties of the enzyme clearly stating that may use in various industrial processes which are performed even at extreme conditions.

Moderately halophilic bacterium, Chromohalobacter salexigens DSM3043, has a gene Csal_2537 encoding thermolysin-like M4 proteinase. This gene was cloned to pET expression vectors, resulting in high expression of recombinant proteinase, named as salilysin ( sali nity-dependent thermo lysin -like proteinase), in Escherichia coli cytoplasm. This gene encodes precursor form of salilysin containing 348 amino acid residues (Pro-salilysin) consisting of 55 amino acids pro-sequence and following mature proteinase. Pro-sequence was cleaved three times to form intermediate 1, intermediate 2 and final mature salilysin. The processing rate was greatly accelerated in a salt concentration-dependent manner. Purified inactive mutant Pro-E167A-salilysin was correctly processed by purified mature salilysin, indicating that autolysis and inter-molecular processing occurred in its maturation processes. Proteolytic activity of mature salilysin against both peptide and protein substrates was also enhanced along with the addition of higher concentration of salt, 0–3.2 M NaCl, consistent with its halophilic origin. Mature salilysin was stabilized by ~8 °C in the presence of 1 M NaCl by thermal scanning using circular dichroism. One of the precursor form, intermediate 1, showed ~20 °C higher denaturation temperature than mature form, suggesting rigid and stable structure of this precursor form.

Salinity is one of the most important growth-limiting factors for most crops in arid and semi-arid regions; however, the use of plant growth-promoting rhizobacteria isolated from saline soils could reduce the effects of saline stress in crops. This study aimed to evaluate the efficiency of plant growth-promoting rhizobacteria (PGPRs), isolated from the rhizosphere of halophile plants, for the growth, Na+/K+ balance, ethylene emission, and gene expression of wheat seedlings (Triticum aestivum L.) grown under saline conditions (100 mmol L−1 NaCl) for 14 d. A total of 118 isolates obtained from saline soils of the deserts of Iran were tested for their capacity as PGPRs. Out of the 118 isolates, 17 could solubilize phosphate (Ca3(PO4)2), 5 could produce siderophores, and 16 could synthesize indole-3-acetic acid. Additionally, PGPRs were also evaluated for aminocyclopropane-1-carboxylate deaminase activity. A pot experiment was conducted to evaluate the ability of 28 PGPR isolates to promote growth, regulate Na+/K+ balance, and decrease ethylene emissions in plants. The most efficient PGPRs were Arthrobacter aurescens, Bacillus atrophaeus, Enterobacter asburiae, and Pseudomonas fluorescens. Gene expression analysis revealed the up-regulation of H+-PPase, HKT1, NHX7, CAT, and APX expression in roots of Enterobacter-inoculated salt-stressed plants. Salt-tolerant rhizobacteria exhibiting plant growth-promoting traits can facilitate the growth of wheat plants under saline conditions. Our results indicate that the isolation of these bacteria may be useful for formulating new inoculants to improve wheat cropping systems in saline soils.

A novel exopolysaccharide, designated hsEPS, was successfully prepared from the high-salt-fermented broth of a novel species Halomonas saliphila LCB169T by ethanol precipitation, anion-exchange and gel-filtration chromatography, and its structure was well-characterized by means of chemical and spectral analyses. Results showed that hsEPS was primarily composed of mannose and glucose with a relative weight-average molecular weight of 5.133 × 104 g/mol. It was deduced that the major backbone contained (1→2)-linked α-D-Manp and (1→6)-linked α-D-Manp with branches substituted at C-2 by T-α-D-Manp and at C-6 by the fragment of T-α-D-Manp-(1→2)-α-D-Manp-(1→. A sheet-like structure was observed under high magnification. The water solubility index, water holding capacity, oil holding capacity and foaming capacity of hsEPS were 98.0, 19.3, 1386.7 and 82.2%, respectively. It also exhibited outstanding emulsifying activity against all tested edible oils. Together, the resulted data indicated that hsEPS might serve as an active ingredient in food, cosmetics and detergents.

The corrosion behavior of 304 stainless steel (SS) in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated. After 14 days of immersion, no obvious pitting pit was observed on the SS surface in the sterile medium. By contrast, the SS exhibited serious pitting corrosion with the largest pit depth of 5.0 μm in the inoculated mediumthe inoculated medium. The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+ and Cr6+ increased in the passive film under the influence of archaea N. tibetense, which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion. Combined with the energy starvation tests, the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N. tibetense was discussed finally.

The adsorption of metal onto archaea could affect metal behavior and bioavailability in hypersaline environments where archaea represent the dominant life form. However, the mechanism and thermodynamics of metal adsorption onto halophilic archaea are not well understood. In this study, Cd adsorption experiments and potentiometric titrations were conducted to model metal adsorption by the halophilic archaeon Halobacterium sp.. Cd adsorption onto the archaeal cells exhibits slow adsorption kinetics, taking 8 h to reach steady-state. The extent of Cd adsorption depends strongly on pCH+ and Cd loading. Desorption of Cd is even slower than adsorption, but exposure of the Cd-adsorbed biomass to high concentrations of cysteine promotes desorption and demonstrates that the distribution of Cd is controlled by reversible adsorption reactions, likely involving sulfhydryl binding of Cd on the cell surface. We conducted potentiometric titration experiments with and without sulfhydryl site blocking to yield a total sulfhydryl site concentration of 91 ± 28 μmol/g within the archaeal cell envelope. Using a combination of the X-ray absorption fine structure analysis results from Showalter et al. (2016) and the Cd adsorption measurements and titration data from this study, we construct a surface complexation model of the Cd adsorption behavior. Because the Cd adsorption behavior is likely similar to that of a range of chalcophilic micronutrients, the importance of Cd-sulfhydryl binding suggests that the production of high affinity sulfhydryl binding sites by the archaea may represent an adaptive strategy for halophiles to obtain metal nutrients in environments in which aqueous metal-chloride complexation dominates the speciation for many metals.

This study is designed to recover and characterize heavy metal resistant halophilic bacteria from Egypt in order to identify mechanisms, plasmids’ role, factors affecting lead (Pb) resistance, and screen for potential industrial and therapeutic enzyme production. Forty-five heavy metal resistant halophilic bacteria were recovered from eleven locations in Lake Qarun, Egypt. The WQL9 isolate showed high Pb resistance up to 4 mM and was resistant to other metals. The 16S rRNA gene analysis and phenotypic characteristics revealed that WQL9 strain belongs to the genus Halomonas. WQL9 growth in Pb-medium supplemented with glucose, yeast, and peptone increased significantly (p

Marine macroalgae have gained considerable attention as renewable biomass sources. Ulvan is a water-soluble anionic polysaccharide, and its depolymerization into fermentable monosaccharides has great potential for the production of bioethanol or high-value food additives. Ulvan lyase from Alteromonas sp. (AsPL) utilizes a β-elimination mechanism to cleave the glycosidic bond between rhamnose 3-sulfate and glucuronic acid, forming an unsaturated uronic acid at the non-reducing end. AsPL was active in the temperature range of 30–50 °C and pH values ranging from 7.5 to 9.5. Furthermore, AsPL was found to be halophilic, showing high activity and stability in the presence of up to 2.5 M NaCl. The apparent Km and kcat values of AsPL are 3.19 ± 0.37 mg mL−1 and 4.19 ± 0.21 s−1, respectively. Crystal structure analysis revealed that AsPL adopts a β-propeller fold with four anti-parallel β-strands in each of the seven propeller blades. The acid residues at the protein surface and two Ca2+ coordination sites contribute to its salt tolerance. The research on ulvan lyase has potential commercial value in the utilization of algal resources for biofuel production to relieve the environmental burden of petrochemicals.

Halophilic α-amylases possess optimal activity in high salt concentrations. Therefore, they can be used in many extreme conditions in industrialised production. In the present work, a halophilic α-amylase (KP) from Klebsiella pneumoniae was characterised, and it exhibited a high specific activity of 3512 U/mg under optimal conditions of 2 M NaCl at 50°C and pH 6.5, but only 97 U/mg in the absence of salt. Furthermore, threonine at position 329 (Thr-329) was found to be related to the non-halophilic properties of KP according to PCR-based site-saturation mutagenesis. The activity of a mutant KP in which this threonine was replaced by aspartic acid was improved 14.6-fold compared with the native enzyme under salt-free conditions, and was increased by 14.8% in the absence of salt. Additionally, the optimal enzymatic properties of KP, including pH and temperature, were altered very little by the amino acid replacement. A further three halophilic α-amylases displayed similar mutational results. The findings provide a reference for bidirectional transformation of KP and similar halophilic enzymes.

Desugarized sugar beet molasses is a high-salinity side stream after fractionation of beet molasses by chromatography. It could be demonstrated that this by-product of the sugar industry is a suitable substrate for the production of poly(3-hydroxybutyrate) with the halophilic bacterium Bacillus megaterium uyuni S29. Cell dry mass concentrations of up to 16.7 g L−1 with a P(3HB) content of 0.6 g g−1 were achieved after only 24 h of batch cultivation. Utilization of a desugarized sugar beet molasses medium resulted in a two- to threefold increase in biomass production compared to a conventional mineral based medium. Depending on the extraction method, the molecular mass (Mn) of the P(3HB) varied between 119 kDa and 722 kDa. The high P(3HB) productivity of 0.42 g L−1 h−1 during batch experiments combined with desugarized sugar beet molasses as inexpensive substrate suggests a simple and robust process for cost effective P(3HB) production.

The genomic and metabolic diversity and features of Tetragenococcus halophilus, a moderately halophilic lactic acid bacterium, were investigated by pan-genome, transcriptome, and metabolite analyses. Phylogenetic analyses based on the 16S rRNA gene and genome sequences of 15 T. halophilus strains revealed their phylogenetic distinctness from other Tetragenococcus species. Pan-genome analysis of the T. halophilus strains showed that their carbohydrate metabolic capabilities were diverse and strain dependent. Aside from one histidine decarboxylase gene in one strain, no decarboxylase gene associated with biogenic amine production was identified from the genomes. However, T. halophilus DSM 20339T produced tyramine without a biogenic amine-producing decarboxylase gene, suggesting the presence of an unidentified tyramine-producing gene. Our reconstruction of the metabolic pathways of these strains showed that T. halophilus harbors a facultative lactic acid fermentation pathway to produce l-lactate, ethanol, acetate, and CO2 from various carbohydrates. The transcriptomic analysis of strain DSM 20339T suggested that T. halophilus may produce more acetate via the heterolactic pathway (including d-ribose metabolism) at high salt conditions. Although genes associated with the metabolism of glycine betaine, proline, glutamate, glutamine, choline, and citrulline were identified from the T. halophilus genomes, the transcriptome and metabolite analyses suggested that glycine betaine was the main compatible solute responding to high salt concentration and that citrulline may play an important role in the coping mechanism against high salinity-induced osmotic stresses. Our results will provide a better understanding of the genome and metabolic features of T. halophilus, which has implications for the food fermentation industry.

Hydroxyectoine, an ectoine derivative, is the most common compatible solute in halophilic microorganisms for resisting harsh environments. Compatible solutes can be utilized in fields such as cosmetics, medicine, and biochemistry. Moderately halophilic microorganisms produce much less hydroxyectoine as compared with ectoine. In this study, we first evaluate the effect of medium formulation (i.e., yeast extract (YE) medium and high yeast extract (HYE) medium) on hydroxyectoine production. In addition, an investigation of hydroxyectoine production by Halomonas salina under optimal conditions for vital factors (i.e., iron and α-ketoglutarate) and hydroxylase activity was also carried out. As a result, hydroxyectoine production was obviously elevated (0.9 g/L to 1.8 g/L) when the HYE medium was utilized. Furthermore, hydroxyectoine production further increased to 2.4 g/L when both the α-ketoglutarate and iron factors were added to the HYE medium in the early stationary phase. In addition, we found that ectoine hydroxylase activity increased more when a combination of iron and α-ketoglutarate was used than when either was used alone. The results showed that the alteration of iron and α-ketoglutarate clearly stimulated the expression of ectoine hydroxylase, which in turn affected hydroxyectoine synthesis. This study also showed that hydroxyectoine production was further raised from 2.4 g/L to 2.9 g/L when 50 mM of α-ketoglutarate and 1 mM of iron were added to the HYE medium. Ultimately, the experimental results showed using the optimal conditions further elevated the hydroxyectoine production yield to 2.90 g/L, which was over 3-fold higher than the best results obtained from the original medium.

Two moderately halophilic and psychrotolerant new Mycoplasma species were isolated from common cephalopods. Three strains were isolated in pure culture from two individual European flying squid (Todarodes sagittatus), and two individual octopuses (Octopus vulgaris). The strains showed optimal growth at 25 °C and a salinity of 3% (w/v) NaCl. Molecular analyses revealed that the isolates belonged to two new, but phylogenetically related species, divergent from all previously described Mollicutes, representing the first marine isolates of the class, and also the first Mycoplasma strains for which NaCl requirement has been demonstrated. A genome search against all available marine metagenomes and 16S rRNA gene databases indicated that these two species represent a novel non-free-living marine lineage of Mollicutes, specifically associated with marine animals. Morphology and physiology were compatible with other members of this group, and genomic and phenotypic analyses demonstrated that these organisms represent two novel species of the genus Mycoplasma, for which the names Mycoplasma marinum sp. nov. and Mycoplasma todarodis sp. nov. are proposed; the type strains are PET (DSM 105487T, CIP 111404T) and 5HT (DSM 105,488T, CIP 111405T), respectively., RRM acknowledges the Spanish Ministry of Economy project CLG2015_66686-C3-1-P also supported with European Regional Development Fund (FEDER) funds. ASR acknowledges the Gobierno de Canarias (Spain) project P2007/046. RRM acknowledges the financial support of the sabbatical stay at Georgia Institute of Technology supported by the grant PRX18/00048 of the Ministry of Sciences, Innovation and Universities. KTK’s research was supported, in part, by the U.S. National Science Foundation (Award No. 1,759,831).

Deep Sea sediment cores were collected from the surrounding of active volcanic Barren Island, Andaman & Nicobar Islands. A total of 123 cultivable marine actinobacteria were isolated and identified based on their biochemical and 16S rDNA sequences. The isolates were categorized under 10 genera, of which Streptomyces sp., Dietzia sp. and Brevibacterium sp. are the dominant genera. Of 123 isolates, 73 isolates exhibited appreciable inhibitory activity against both Gram positive and Gram negative bacteria. High frequencies of positive PCR amplification were obtained for PKS-I (39.13%), PKS-II (56.52%) and NRPS (69.57%). The highest levels of biosynthetic systems were observed for NRPS and PKS-II. Majority of the actinobacterial isolates revealed excellent potential for bioprospecting of novel byproducts with industrial and pharmaceutical importance.

The idea at the core of the research reported in the present paper is the use of indigenous halophilic consortia of an oilfield for treatment of the produced water (PW) generated in the same oilfield. To test this idea water and soil-based microbial sources obtained from desalination units of two oilfields were enriched in PW obtained from the same oilfield and supplemented with either yeast extract (YE) or Mueller-Hinton medium containing crude oil. Enriched soil-based microbial consortia (termed EVPS) gave a meaningfully higher maximum achievable biomass concentration, and amount of COD removed when grown on PW supplemented with YE compared to enriched water based ones. The supplementation of PW with inorganic nitrogen and phosphorous sources resulted in around 35% COD removal whereas supplementation with YE increased the PW COD removal to 62%. Microbial analysis of EVPS with Illumina HiSeq/MiSeq showed that bacteria had higher richness and diversity than archaea. The dominant bacteria genera were Chromohalobacter, Idiomarina, and Marinobacter, whereas Haloterrigena, Haloferax, and Methanohalophilus were the dominant genera amongst the archaea. Based on previous reports, the identified genera in EVPS have a wide salt tolerance range and are collectively capable of biodegrading most of the organic compounds prevalent in PW.

The growth and yield of plants, including halophytes, are widely affected by salinity. It is known that the rhizosphere and endorhiza of the plants growing in saline environments harbor salinity–tolerant bacteria with plant growth promoting (PGP) potential. However, information about PGP endophytic and rhizosphere bacteria colonizing in the halophytes is still scarce. This study was designed to isolate and characterize rhizosphere and endophytic bacterial isolates from salt–accumulating halophyte Salicornia sp. grown under extreme salinity and to evaluate the effect of effective rhizosphere and endophytic bacterial strains (no bacteria, B0; rhizosphere strain Staphylococcus sp., R; endophytic strain Staphylococcus sp., E; and combination of these strains, R + E) on Salicornia sp.–plant growth promotion under salinity stress (0, 200, 400, and 600 mM NaCl) in greenhouse conditions. A total of 214 rhizosphere and endophytic isolates were obtained from rhizosphere soil and the surface–sterilized roots of Salicornia sp. These isolates exhibited tolerance to NaCl and drought and had different PGP traits. The results of this study also showed that the growth of the halophyte Salicornia sp. was also affected by salinity. At level of 200 mM NaCl, salinity had a positive effect on plant growth, so that the highest growth indices of the plant were observed at this salinity level. However, at salinity levels higher than 200 mM NaCl (400 and 600 mM NaCl), the growth of the plant (5.8–42.9% decrease in growth indices) decreased compared to that of this plant at the concentration of 200 mM NaCl. Bacterial strains (R, E, and R + E) had a positive role in alleviating the negative effects of salinity on the plant growth (13.9–47.0% increase in growth indices) compared to control (B0) at all salinity levels. In the presence of the bacterial strains (R, E, and R + E), the highest plant growth (33.2–65.2% increase in growth indices) was obtained at a concentration of 200 mM NaCl. Among bacterial treatments, the combination of these strains (R + E) had the highest effect on the plant growth under salinity stress. In general, the results of this study show that salinity–tolerant rhizosphere and endophytic bacteria associated with the halophyte Salicornia sp. have an important role in enhancing growth and salt tolerance in the halophyte Salicornia sp. and can be used as bio–fertilizer for further improvement of the growth of this plant in saline environments.

Pre-treatment of lignocellulosic biomass is essential for the cost-effective saccharification process to produce fermentable sugars. In this study, Deep Eutectic Solvents (DESs) and halophilic cellulase system were used as a new green and cost-effective approach for lignocellulose hydrolysis. The stability and compatibility between DES and halophilic cellulase for lignocellulose hydrolysis were investigated by monitoring the stability of halophilic cellulase in the occurrence of different concentrations of DESs. It was found that halophilic cellulase showed higher stability in the occurrence of 10–20% (v/v) DES. It has been noticed that 20% of DESs, enhanced 2–3 folds in the release of glucose. The compatibility of the DES-halophilic cellulase system has been further evaluated and improved the saccharification efficiency even at high solid loadings. Using the system, saccharification of the rice husk produced three folds of glucose higher than the untreated sample. The yield was estimated to be higher than 1 mM of glucose using the halophilic cellulase-DES system with the hydrolysis for 36 h. DESs-halophilic cellulase system offers a good alternative compared to the available lignocelluloses pre-treatment method in terms of cost, environmental and compatibility with enzyme aspects.

Polycyclic aromatic hydrocarbons (PAH) and pharmaceutical compounds (PhC) are xenobiotics present in many saline wastewaters. Although fungi are known for their ability to remove xenobiotics, the potential of halophilic fungi to degrade highly persistent pollutants was not yet investigated. The use of two halophilic fungi, Aspergillus sydowii and Aspergillus destruens, for the elimination of PAH and PhC at saline conditions was studied. In saline synthetic medium both fungi used benzo-α-pyrene and phenanthrene as sole carbon source and removed over 90% of both PAH, A. sydowii due to biodegradation and A. destruens to bioadsorption. They removed 100% of a mixture of fifteen PAH in saline biorefinery wastewater. Test using Cucumis sativus demonstrated that wastewater treated with the two fungi lowered considerably the phytotoxicity. This study is the first demonstration that ascomycetous halophilic fungi, in contrast to other fungi (and in particular basidiomycetes) can be used for mycotreatments under salinity conditions.

The issue of dye disposal into the environment has received considerable critical attention. Therefore, this study aims to investigate the biodegradation and detoxification of Solvent Green 3 (SG3) by halophilic Hortaea sp. For toxicity examination, SG3 (before and after degradation) was inspected against two plants, which are Sorghum vulgare and Triticum aestivum. The maximum specific growth rate of the bacterium was 0.13 h−1. The fastest duration for the complete removal of the dye and chemical oxygen demand was achieved at the lowest concentration of the dye. The presence of Cu2+ performed a higher removal capability compared to other employed metal ions. The 1,2-dioxygenase performed the highest enzymatic activity (up to 488 U/L). The 1,2-dioxygenase and laccase were responsible for the biodegradation and detoxification of SG3. SG3 can be degraded by Hortaea sp. into lower toxicity compounds via two routes, which are initially transformed into 1,4-diaminoanthracene-9,10-dione and p-toluidine before degraded into phthalic acid and 4-hydroxybenzoic acid, respectively. The biodegraded product of SG3 achieved better the germination percentage, plumule, and radical lengths of the plants compared to SG3. In general, this study revealed that the dye can be completely removed by the bacterium and can be transformed into lower toxicity compounds.

Salinity represents one of the environmental conditions with adverse effects on the productivity of most crops throughout the world. The response of plants to salt stress is of great interest for research to understand the mechanism involved in tolerance to salinity and highlight insights into the improvement of salt tolerance-crops of importance. In this study, the effect of salt stress was observed in wild and cultivated populations of P. oleracea originated from Tunisia and Italy. The results showed that at various concentrations of NaCl (0 mM, 50 mM, 100 mM and 150 mM), salinity has led to changes in growth parameters marked mainly by an increase in fresh and dry biomass. Beside, one of the salinity-induced side effects corresponds to the competition of Na+ and K+ ions for potassium root transporters. Our results suggested that purslane deployed an important element of tolerance such as the transporters ability to discriminate cations. In addition, the variation of PC5S gene expression tested by semi-quantitative RT-PCR revealed that proline synthesis is important in plants adaptation in saline conditions. A correlation between the gene expression varying by population and saline concentration and the level of proline assayed on the leaves of P. oleracea was highlighted.

The productivity of cold-active polygalacturonase (PGase) in a newly identified marine psychrophile, Thalassospira frigidphilosprofundus S3BA12, was increased multifold by employing high-cell-density (HCD) culturing in a simulation-assisted, custom-designed single-stage-continuous immobilized reactor. The reactor was made “halophilic culturing” ready by using surface altered polyurethane foam (PUF) as a matrix, and it was uniquely packed with layers of “spacers” to increase robustness towards high salinity, prevent salt deposition and dissociation of cells. The basic limitation of low growth of a marine organism was overcome in this study, where HCD resulted in a 4-fold increase of cell mass from 0.84 dcw g/L in submerged culture to 3.22 g/L, which commensurately increased the PGase titre from 21.0 U/ml to 85.25 U/ml. The culture was sustained for 108 h, continuously producing PGase at a rate of 7.87 U/ml hr−1. This could be the highest reported cold-active PGase by any psychrophilic organism reported to date. A mechanistic modelling approach was used to develop a simulation of the process in ChemCAD 5.0, which can be used as a basis for scale-up studies. This study proved statistically that PGase titre is significantly dependent on cell mass using Anderson-Darlington normality tests and established a correlation between PGase and other pectinase subtypes using Pearson’s correlation coefficient analysis.

From the halophilic bacteria to human, cells have to survive under the stresses of harsh environments. Hyperosmotic stress is a process that triggers cell shrinkage, oxidative stress, DNA damage, and apoptosis and it potentially contributes to a number of human diseases. Remarkably, by high salts and organic solutes concentrations, a variety of organisms struggle with these conditions. Different strategies have been developed for cellular osmotic adaptations among which organic osmolyte synthesis/accumulation is a conserved once. Osmolytes are naturally occurring solutes used by cells of several halophilic (micro) organisms to preserve cell volume and function. In this review, the osmolytes diversity and their protective roles in harsh hyperosmolar environments from bacteria to human cells are highlighted. Moreover, it provides a close look at mammalian kidney osmoregulation at a molecular level. This review provides a concise view on the recent developments and advancements on the applications of osmolytes. Identification of disease-related osmolytes and their targeted-delivery may be used as a therapeutic measurement for treatment of the pathological conditions and the inherited diseases related to protein misfolding and aggregation. The molecular and cellular aspects of cell adaptation against harsh environmental osmolarity will benefit the development of effective drugs for many diseases.

Halomonas ventosae RU5S2EL, a halophilic Gram-negative bacterium isolated from salt sediments of lake Elton (Russia), was cultivated and the lipopolysaccharide was extracted by the Westphal procedure. The O-specific polysaccharide (OPS) was obtained by mild acid hydrolysis of the lipopolysaccharide and was studied by sugar analysis along with 1H and 13C NMR spectroscopy, including 1H,1H COSY, TOCSY, ROESY, 1H,13C HSQC, and HMBC experiments as well as Smith degradation. The OPS was found to consist of branched pentasaccharide repeating units of the following structure.

The hydrolysis step by β-glucosidase (BGL) is generally recognized as the major limiting step in cellulose degradation and the BGLs with prominent enzymatic properties are of great importance for efficient utilization of lignocellulosic biomass. In order to identify some salt-tolerant BGLs, two BGL genes were cloned from marine Aspergillus niger ZJUBE-1 genome. Then two bgl expression cassettes driven by gpdA promoter were respectively transformed into marine A. niger for homologous constitutive expression. Directed expression was achieved for the domination of target BGLs in fermentation broth. Conveniently, two BGLs were purified to homogeneity by two separation steps, ultrafiltration and anion exchange chromatography. The purified BGL1 and BGL2 showed maximum activity at pH 3.0-4.0 and 3.5-4.5, respectively, suggesting these two BGLs were relatively acidophilic, especially for BGL1. Besides, BGL1 was stable to most of metal ions, while BGL2 was sensitive to Cu2+, Fe3+ and Ag+. Most specially, BGL2 activity increased by 44% in the presence of 4 M NaCl, suggesting BGL2 was halophilic. Homology modeling revealed that longer loops and linkers as well as polymerous Glu492 may contribute to the halophilism of BGL2. At last, the medium for directed expression was optimized and the content as well as the purity of target protein was improved.

Habitat salinity is a major abiotic factor governing the activity, physiology, biology and distribution of aquatic animals. Salinity changes cause salt stress, affecting crustaceans reared in aquaculture both on an ecological and economic level. Current salt stress research in aquatic animals is mainly focused on salt stress in the gills at relatively low salinity ranges. Knowledge about whole-body salinity response in crustaceans and other organisms is lacking, especially in hypersaline conditions. Artemia franciscana is a small halophilic model crustacean able to withstand high salinities up to 300 g/l and strong osmotic shocks thanks to its mitigating strategies for fluctuating salinity levels, such as its unique larval salt gland and osmoregulatory capacity. This study aims to identify the genes responsible for Artemia's unique hypersalinity tolerance by differential expression analysis. First, the full transcriptome of A. franciscana in different metabolic and life cycle stages was assembled de novo (assembly statistics: N50 = 1,430; GC content = 35.63%; transcript number = 64,972) and functionally annotated (annotated transcripts = 36%). Then, naupliar RNA-Seq reads generated under respectively hypersaline and marine conditions were pseudo-aligned to the A. franciscana transcriptome. Expression levels in both conditions were finally compared and 177 differentially expressed, functionally annotated transcripts were identified, of which 113 transcripts with GO annotations. Signalling genes, such as EIF and several genes from the glutathione and the chitin metabolic pathways were induced in Artemia under hypersaline conditions. Hypersalinity also activated gene regulation mechanisms (expression, transcription and post transcription) in the nucleus for DNA repair, ubiquitination, and also for cell cycle arrest through La-related protein. Several lipid metabolic genes and lipid transporters were upregulated, potentially to provide energy for ion balance and to maintain membrane structure integrity. Transport of metal ions and other ions was upregulated as well to maintain ion homeostasis. Lastly, known crustacean stress response genes such as Heat shock 70 kDa protein cognate were upregulated. This work shows that salt stress in Artemia nauplii, through signal transduction, gene regulation, lipid metabolism, transport and stress response genes, has an important influence on known and novel homeostasis-repairing mechanisms in Artemia.

International audience; A novel anaerobic methylotrophic halophilic methanogen strain SLHTYRO T was isolated from a deep hypersaline anoxic basin called "Tyro" located in the Eastern Mediterranean Sea. Cells of SLHTYRO T were motile cocci. The strain SLHTYRO T grew between 12 and 37 °C (optimum 30 °C), at pH between 6.5 and 8.2 (optimum pH 7.5) and salinity from 45 to 240 g L −1 NaCl (optimum 135 g L −1). Strain SLHTYRO T was methylotrophic methanogen able to use methylated compounds (trimethylamine, dimethylamine, monomethylamine and methanol). Strain SLHTYRO T was able to grow at in situ hydrostatic pressure and temperature conditions (35 MPa, 14 °C). Phylogenetic analysis based on 16S rRNA gene and mcrA gene sequences indicated that strain SLHTYRO T was affiliated to genus Methanohalophilus within the order Methanosarcinales. It shared >99.16% of the 16S rRNA gene sequence similarity with strains of other Methanohalophilus species. Based on ANIb, AAI and dDDH measurements, and the physiological properties of the novel isolate, we propose that strain SLHTYRO T should be classified as a representative of a novel species, for which the name Methanohalophilus profundi sp. nov. is proposed; the type strain is SLHTYRO T (=DSM 108854 = JCM 32768 = UBOCC-M-3308).

Biocatalysis has become the main approach to produce cytidine diphosphate choline (CDP-choline), which has been applied for treatment of acute craniocerebral injury and consciousness after brain surgery. However, salt accumulates with the production and inhibits enzyme activity, and eventually reduces yield and product accumulation rate. Our work provided a possible solution to this problem by applying a computational designed halophilic choline kinase. The halotolerant CKI (choline kinase) was designed following a unique strategy considering the most variable residue positions on the protein surface among target enzymes from different sources. The basic and neutral surface residues were replaced with acidic ones. This approach was enlightened by features of natural halophilic enzymes. Mutants in the work represented higher catalytic activities and IC50 (inhibit activity by 50%) at high salt concentrations (over 1200 mM). Furthermore, when the mutant was used in fed-batch production, the CDP-choline accumulation rate doubled comparing with process using wild-type CKI at acetate concentration of over 700 mM. The maximum titer was 151 ± 3.2 mM, the productivity was 5.8 ± 0.1 mM·L−1 h−1, and molar yield to CMP and utilization efficiency of energy were 85.3 and 63.5%. The idea of computational design in our work can also be applied to modify other enzymes in industry, and sheds light on alleviating effect of salt accumulation during industrial manufacturing process.

The present study reports the isolation of protease producing bacteria Bact2 from agricultural soil of Regional Centre of Soil Salinity Research Institute, Lucknow, India. It was identified as Citricoccus sp. (KC522120.1) by 16S rRNA gene sequencing. The optimum pH and temperature for maximum enzyme production was observed to be at 10 and 40 °C respectively. The enzyme protease was partially purified and recovery of enzyme was 77.16%. A 1.66 fold increase in enzyme activity was also observed in comparison to original. After purification, the partially purified enzyme (PPE) was characterized. The optimum pH and temperature of partially purified enzyme (PPE) activity was observed to be at 10 and 40 °C respectively. The activity of PPE was enhanced in presence of Ca2+ and Mg2+ while it was inhibited by Cu++ and Na+. The PPE was completely inhibited by Phenyl methyl sulphonyl fluoride (PMSF) indicating that it belongs to serine protease group. Finally, enzyme was found to be compatible with detergents and effective in removing stains of tea and ink indicating it's application in detergent industry. Besides, to our knowledge till date production of alkaline protease from Citricoccus sp. has been reported first time in the present manuscript.

Trimatostroma salinum, Wallemia ichthyophaga, Hortaea werneckii and Phaeotheca triangularis are halophilic fungi, which can thrive in a wide range of salinity (0%–32% NaCl). They present a source of valuable bio-active compounds, enzymes and proteins interesting for environmental management, food, textile and pharmaceutical industry. Enzymes from these fungi, e.g. amylases, cellulases, lipases, and proteases, which possess so called polyextremophilicity (they are thermostable, tolerant to a wide range of pH, less susceptible to denaturation and tolerant to high salt concentrations) present a novel catalytic alternative for biotechnological applications. To release enzymes from halophilic fungi cells, a conventional method using mechanical homogenizer (rotor-stator homogenizer) and a novel method using supercritical technology were applied. Very high protein concentration in all halophilic fungi cell suspensions after the treatment with SC CO2 were detected. Obtained results also show very high activities of protease, α-amylase, β-glucosidase and cellulase after the treatment of each halophilic fungi cell suspension by SC CO2. Using SC CO2 as a medium for cell disruption offers additional benefits regarding performance of a biochemical reaction and bioseparation in the same medium leading in integration of all three processes into a single step. Besides, integration of processes presents important advantage in industrial processes from an economic point of view. Enzymes from extremophiles namely possess improved properties and can be used at harsh conditions where non-extremophilic enzymes may deactivate. Therefore, extremozymes from T. salinum, W. ichthyophaga, H. werneckii and P. triangularis are as high-pressure tolerant enzymes suitable for many industrial applications, which could be performed also in non-aqueous media like SC CO2.

The influence of aerobic halophilic archaea Natronorubrum tibetense on the corrosion of Q235 carbon steel was investigated. In immersion tests, more serious corrosion was observed in the N. tibetense-inoculated medium than in the sterile medium. Compared with the uniform corrosion morphologies in the sterile medium, severe localized corrosion occurred in the inoculated medium. After 14 days of immersion, the presence of N. tibetense caused a weight loss of 0.051 g/cm2 of the steel, which was about two times larger than that in sterile medium (0.026 g/cm2). The starved N. tibetense exhibited more aggressive MIC against the steel when organic sources were deficient.

In this study, the differential protein expression of the acidophilic halophile , Acidihalobacter prosperus DSM 14174 (strain V6) was studied with the aim of understanding its mechanisms of tolerance to high chloride ion stress in the presence of low pH, using Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH-MS). In acidophiles , chloride stress results in both osmotic stress as well as acidification of the cytoplasm due to the ability of chloride to permeate the cell membrane and disrupt the reversed transmembrane potential which normally extrudes protons. The proteomic response of A. prosperus DSM 14174 to elevated chloride concentrations included the production of osmotic stress regulators that potentially induced the production of compatibles solutes , of which the most significant increase was in the synthesis of ectoine. Other responses directly related to the increased chloride and acid stress, included the increased synthesis of glutathione, changes in carbon flux, the increased production of amino acids, the decreased production of ribosomal proteins, the efflux of metals and protons, and the increase in proteins involved in DNA repair and membrane biosynthesis . Energy generation through iron oxidation and sulphur oxidation were decreased, and energy was probably obtained from the metabolism of glycogen stores. Overall, these studies have helped to create a model of tolerance to elevated chloride under acidic conditions by A. prosperus DSM 14174 that differs from the previous model developed for the type strain, A. prosperus DSM 5130T.

The present study demonstrates pyrene degradation by a pshychrophilic bacterial strain, Shewanella sp. ISTPL2 isolated from Pangong lake, Ladakh, India. The ISTPL2 strain showed highest specific growth rate at 500 ppm with 93% extent of degradation. Pyrene metabolic pathway was confirmed from metabolites such as 4,5-dihydroxypyrene, 2-carboxybenzalpyruvate, phthalic acid and salicylic acid obtained from pyrene degradation. Soil microcosm was set up with different concentration of pyrene and investigated using GC–MS to uncover the arrangement of intermediary metabolites. The results indicated that 75.11%, 95.39%, 94.32% and 93.11% of pyrene was degraded within 90 days in the soil spiked with 50, 350, 500 and 1000 ppm pyrene respectively. Strain ISTPL2 is a potent candidate for pyrene degradation as it can survive under high pyrene load.

The aerobic granular sludge (AGS) dominated by halophilic microorganisms, was successfully cultivated in a lab-scale sequencing batch reactor (SBR) under varying salinity levels (from 0% to 6% (w/v)). Removal performance of AGS improved with the increase of salinity and increased up to 42.86 mg g−1 VSS h−1 at 6% salinity. Increased salinity resulted in better settling performance of AGS in terms of the sludge volume index (SVI), which was initially 148.80 mL/g at 0% salinity and gradually decreased to 59.1 mL/g at 6% salinity. The increase of salinity stimulated bacteria to secret excessive extracellular polymeric substances (EPS), with its highest production of 725.5 mg/(g·VSS) at 5% salinity. The total protein (PN) exhibited highly positive correlation with the total EPS (R = 0.951), indicating that selective secretion of some functional PN played a key constituent in resisting the external osmotic pressure and improving sludge performance. Salinicola, accounted for up to 91% relative abundance at 6% salinity, showed the high positive correlation (R = 0.953) with salinity. The enrichment of such halophilic or halotolerant microbial community assured both stable and improved removal performance in the AGS system. The enrichment of salt response pathways and altered metabolic processes for salt-tolerant bacteria indicated that the microbial community formed special metabolic pattern under long-term hypersaline stress to maintain favourable cellular activity and removal performance.

Sea barley (Hordeum marinum) is a wild species belonging to halophytes, while other Hordeum species are glycophytes. In this study, we aimed to understand molecular differences of transcriptomic and metabolomic responses and uncover complex mechanisms underlying salt tolerance between H. marinum and H. vulgare. Physiological studies revealed that sea barley accession H559 had less growth inhibition, higher root K+ concentration, lower shoot Na+ accumulation and higher shoot osmotic potential than barley genotypes XZ113 and Golden Promise under 400 mM salinity stress. The superior Na+/K+ homeostasis in H559 may depend on the regulation of ion transporters including SOS1, HKT1;1, HKT1;5 and HKT2;2 according to RNA-seq analysis. The comparison of metabolite and transcript profiles among three genotypes indicated that H559 used less energy-consuming strategies including a larger scale gene down-regulation and utilization of inorganic ions (i.e. Na+ and K+) as “cheap” osmotica for root tolerance, and enhanced glycolysis and the TCA cycle for energy supply and compatible solutes accumulation for shoot tolerance. Moreover, some genes involved in the ROS detoxification were also identified in H559. We propose that the salt tolerance in the halophyte sea barley is correlated with superior Na+/K+ homeostasis, energy-saving strategy and osmotic adjustments in tissues. The present results provide the fundamental evidences at molecular level for explaining why H. marinum has higher salt tolerance than H. vulgare.

We present the draft genome sequence of Halobacillus sp. BBL2006, a moderately halophilic, gram positive bacterium isolated from a sulfidic salt spring in Big Bone Lick State Park, Boone County, Kentucky. The genome of Halobacillus sp. BBL2006 was 3,988,138 bp in length with a GC content of 41.6%. Genome analysis identified 4331 open reading frames including genes for antibiotic resistance and tolerance to heavy metals. The draft genome was deposited at DDBJ/EMBL/GenBank (DNA Databank of Japan/European Molecular Biology Laboratory/Genbank) (JRNX00000000).

The taxonomic diversity of the microbial communities associated with stable 30-y old cheese brines from an artisan and large-scale cheese producer located in Flanders, Belgium, was investigated culture-independently. High-throughput amplicon and shotgun metagenomic sequencing revealed species of Tetragenococcus, Chromohalobacter, and Halanaerobium as the most abundant ones in both brines. Debaryomyces was the only yeast genus detected. All these halophiles might originate from the salt used and might survive and even grow in the brines. The occurrence of different and/or additional species in the two brines could be due to differences in salt concentrations. A second group of microorganisms, possibly incapable of growth in the brines, could be mainly associated with the cheese production ingredients, such as the rennet (Lactobacillus rennini), starter culture (Lactococcus lactis) or raw milk used (Lc. lactis and Staphylococcus equorum). This specific brine microbiota might have an impact on the ultimate quality of the cheeses produced.

Deep Sea sediment cores were collected from the surrounding of active volcanic Barren Island, Andaman & Nicobar Islands. A total of 24 halophilic eubacteria were isolated and identified based on their biochemical and 16S rDNA sequences. Three major classes ( Gamma-Proteobacteria , Alpha - Proteobacteria and Bacilli ) of bacteria were detected in the deep sea sediments of active volcanic Barren Island. Among those, 37% of isolates exhibited antimicrobial activity against all tested Gram positive and Gram negative clinical pathogens. 60% of isolates revealed the presence of either PKS or NRPS genes and 65% isolates disclosed medium to higher level of cytotoxicity in MB-231 breast cancer cell line. Majority of the isolates revealed excellent potential for bioprospecting of novel byproducts with industrial and pharmaceutical importance.

This study is a new trial aimed to solve levansucrase high cost and levan associated problems during the purification process. Also, kinetic and thermodynamic study was done to compare between the partial pure (PP) and purified forms (PF). Within this context, Aspergillus awamori EM66 levansucrase was produced constitutively (5.44 U.mL−1) using rice straw as the sole medium component. The enzyme was partially purified and was eluted as single protein after two purification steps. Its molecular weight was determined to be 44.5 KDa. The optimum temperature recorded 40 °C for both enzyme forms. While, the purification process lowering the enzyme pH from 5.2 to 4.0. The NaCl concentrations (0.5-3.0 M) pointed to the halophilic nature of the enzyme. The PP form retained about 76% of its original activity after 1 h at 55 °C while the other retained about 57% after 45 min. at the same temperature. The kinetic parameters Km and Vmax concluded that the PF was more efficient than the PP. The thermodynamic parameters such as Ea, Ed, T1/2, D-value, also, ∆G*, ∆H* and ∆ S* for activation recorded that the PP had higher stability than the PF.

Proteases are universal in existence in all organisms and are needed for metabolic activities of the cell. Also, proteases are the paramount hydrolytic enzymes widely used in industrial sector accounting ~65% of the aggregate worldwide enzyme market. The market revenue of global protease sale is estimated to be $ 2.21 billion by 2021. Currently, a widening expectation of biotechnology sector necessitates the availability of robust protease with industrially suitable operative features. The commercially-compatible protease should show stability and altered specificity in organic solvents, and be economically as well as ecologically sustainable. The proteolytic halophilic and halotolerant microorganisms are a novel source of salt-stable proteases. Beside stable in the presence of significant amount of salt, the halo-proteases could occasionally display the polyextremophilic attributes like tolerance to alkaline pH, high temperature, and organic solvent tolerance etc. This review describes - halophilic/halotolerant proteolytic microorganisms as source of salt-stable protease, mechanisms of high salt tolerance, various physical and nutritional parameters affecting the protease production, purification strategies for protease, characteristics of salt-stable proteases, and commercial significance of salt-stable proteases. The study revises the current status of the research on salt-stable proteases obtained from extremophile with their operative utility in the biotechnology field.

Levan is a fructan type polysaccharide that has long been considered as an industrially important biopolymer however its limited availability is mainly due to the bottlenecks associated with its large-scale production. To overcome such bottlenecks in the commercialization of this very promising polysaccharide, co-production of levan with polyhydroxyalkanoates (PHAs) by halophilic Halomonas smyrnensis cultures has been proposed in this study for the first time. After in silico and in vitro assessment of PHA accumulation, fermentation profiles for levan and PHA concentrations were obtained in the presence of sucrose and glucose and the PHA granules observed by TEM were found to be poly(3-hydroxybutyrate) (PHB) after detailed structural characterization by GC-MS, DSC, FTIR and NMR. Six nutrient limitation strategies based on nitrogen (N) and phosphorus (P) were tested but highest levan and PHB yields were obtained under unlimited conditions. H. smyrnensis is proved to co-produce PHB and levan while using inexpensive carbon sources which is a commercially successful microbial cell factory system showing a great potential in lowering manufacturing costs and aiming for a zero waste policy within the biorefinery concept. (C) 2018 Elsevier B.V. All rights reserved.

Carotenoids are antioxidant compounds have been used for human benefits and in many industrial applications. The halophilic microalga Dunaliella parva is rich with natural carotenoids such as β-carotene. To enhance carotenogenesis, an external phytoene synthase gene (PSY) from Synechocystis sp. strain PCC 6803 was successfully cloned into D. parva cells (D-PSY). D-PSY showed higher carotenoids value (3.8 mg g−1 DW) compared to the wild-type (WT) strain (2.5 mg g−1 DW). For further assessment, both WT and D-PSY strains were subjected to two different stresses (polyethylene glycol (PEG) and CaCl2). Application of CaCl2 enhanced the chlorophylls (Chl a, Chl b) and carotenoids contents of both strains compared to PEG. The maximum carotenoids contents were obtained by treatment of D-PSY strain with 30 ppm PEG (7.0 mg g−1 DW) and 60 ppm CaCl2 (6.0 mg g−1 DW). The soluble carbohydrates contents of D-PSY cells recorded high value (83.5 mg g−1 DW) compared to that of WT strain (52 mg g−1 DW). While 60 ppm CaCl2 significantly stimulated the carbohydrate contents of both WT and D-PSY (58.4 and 117 mg g−1 DW, respectively), 30 ppm PEG showed an inhibitory effect (50.4 and 58.5 mg g−1 DW of WT and D-PSY, respectively). The antioxidant activities of the carotenoids samples were analyzed through five different assays. Generally, the antioxidant activities of D-PSY carotenoids were superior to that of WT. Moreover, stress applications (30 ppm PEG and 60 ppm CaCl2) enhanced the antioxidant activities of the carotenoids samples of both strains.

This study aim to evaluate the potential toxic effects of citrate coated silver nanoparticles (AgNPs) and ionic silver (AgNO3) on marine microalgae Dunaliella salina under three different salinities (35, 70, and 140 g/L). The toxicity was investigated according to modified OECD guideline (No. 201) by 72 h exposure of microalgae to various concentrations of each of the chemicals in Walne's saline media. According to the results, the growth inhibitory effects of AgNPs and AgNO3 increased significantly coincidence with increasing time and concentration compared to control (P

Saline and hypersaline environments make up the largest ecosystem on earth and the organisms living in such water-restricted environments have developed unique ways to cope with high salinity. As such these organisms not only carry significant industrial potential in a world where freshwater supplies are rapidly diminishing, but they also shed light upon the origins and extremes of life. One largely overlooked and potentially important feature of many salt-loving organisms is their ability to produce fructans, fructose polymers widely found in various mesophilic Eubacteria and plants, with potential functions as storage carbohydrates, aiding stress tolerance, and acting as virulence factors or signaling molecules. Intriguingly, within the whole archaeal domain of life, Archaea possessing putative fructan biosynthetic enzymes were found to belong to the extremely halophilic class of Halobacteria only, indicating a strong, yet unexplored link between the fructan syndrome and salinity. In fact, this link may indeed lead to novel strategies in fighting the global salinization problem. Hence this review explores the unknown world of fructanogenic salt-loving organisms, where water scarcity is the main stress factor for life. Within this scope, prokaryotes and plants of the saline world are discussed in detail, with special emphasis on their salt adaptation mechanisms, the potential roles of fructans and fructosyltransferase enzymes in adaptation and survival as well as future aspects for all fructanogenic salt-loving domains of life.

Ectoine, a cyclic tetrahydropyrimidine (2-methyl-1,4,5,6-tetrahydropyrimidine-4-carboxylic acid) is a natural compound, which serves as a protective substance in many halophilic bacterial cells. Ectoine biosynthesis genes (ectA, B and C) were PCR amplified from the genomic DNA of deep sea eubacteria, Bacillus clausii NIOT-DSB04. The amplified genes were cloned and nucleotide sequences were determined. Sequencing results revealed that ectA, B and C genes contains 537 bp, 1281 bp, 405 bp long ORF encoding 178, 426 and 134 amino acids, respectively. In silico sequence and phylogenetic analysis of nucleotides and amino acids revealed that the ectA, B and C sequences of Bacillus clausii NIOT-DSB04 were conserved in many eubacteria.

Lipase secretion by halophilic strains under solid state fermentation has been relatively understudied, especially when utilizing agro-industrial substrates. Eleven halophilic bacterial strains were locally isolated and screened for lipase secretion. All the strains were subsequently subjected to the screening on various agro-industrial substrates for the lipase production, and to assess the best supporting substrate. The halophilic strain with the maximum lipase secretion (0.264 U/g) potential was selected and identified as Bacillus amyloliquefaciens AIKK2. Coconut fibre was found the best supporting substrate for halophilic lipase secretion and influence of nutritional and environmental parameters on halophilic lipase secretion was determined using One-Factor-At-A-Time. The optimized experiment was conducted at 6% glucose, 9% NaCl, 40 °C, and 200 rpm agitation speed resulted in the enhanced lipase secretion (0.29 U/g). Further, halophilic lipase characterization studies revealed that the enzyme was thermally stable at 50 °C, showed the improved activity at moderate NaCl and rare tolerance in hydrophilic solvents.

The moderately halophilic bacterium, Virgibacillus halodenitrificans PDB-F2, is able to degrade phenol in high-salinity environment, which copes with external salinity fluctuation by biosynthesis or uptake of compatible solutes. Four putative compatible solutes transport systems BetL, OpuD1, OpuD2 and OpuD3, which belong to betaine-carnitine-choline transporters (BCCT) family, have been predicted from the complete genome sequence of V. halodenitrificans PDB-F2. This study investigated the responses of four transport genes betL, opuD1, opuD2 and opuD3 to NaCl stress in V. halodenitrificans PDB-F2. Transcriptional analysis showed that betL, opuD1, opuD2 and opuD3 were induced by NaCl stress, and had specificity for glycine betaine (GB). The maximal induction of four transport genes transcription depended on high salinity plus GB. Exogenous GB afforded effective osmoprotection for V. halodenitrificans PDB-F2 at high salinity, especially at 15% (wt/vol) NaCl. Escherichia coli MHK13 is a mutant strain which is unable to grow at high salt condition. We examined the growth of E. coli MHK13 complemented with each of four transport genes and examined the uptake of GB in cells by 1H nuclear magnetic resonance (1H NMR) spectroscopy under high salt condition. These data showed that all four transporters were able to transport GB.

Carbonic anhydrase (CA), an enzyme that catalyzes the carbon dioxide (CO2) hydration, has been suggested as a potentially powerful agent for CO2 capture and utilization. For successful application, CA should withstand the harsh environment presented by CO2-capturing facilities. While there have been intensive efforts to identify and engineer thermostable CAs, other required conditions such as the high salt concentration of CO2 absorbents have often been ignored. Herein, we expressed, purified, and characterized a novel α-type CA (hmCA) possessing an unusual N-terminal extension from the halophilic marine bacterium Hydrogenovibrio marinus. We found that the N-terminal extension strongly influenced the enzyme solubility. Recombinant hmCA showed catalytic efficiency comparable to other bacterial α-type CAs. hmCA was less inhibited by anionic inhibitors showing 1.6- (NO3−), 3.1- (NO2−), and 3.7-fold (Cl−) higher inhibition constants than those of mesophilic bovine CA (bCA), suggesting halotolerance. Recombinant hmCA was markedly stabilized using most of the alkali metal salts tested, showing 19 °C higher melting temperature at 1 M NaCl compared to bCA that was significantly destabilized. The region of N-terminal extension seemed not to be involved in halotolerance. The remarkable halotolerance may be attributed to the uneven distribution of electrostatic potential and the localized negative charge on the hmCA surface. hmCA displayed ∼29-fold longer half-life than that of bCA at 40 °C in potassium carbonate as a practical absorbent, suggesting that halotolerance should be considered another key characteristic in the development of biocatalysts for CO2 capture using high-salt-containing CO2 absorbents.