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Introduction: Infectious keratitis, an inflammatory condition of the cornea, poses a significant public health concern globally. Bacterial keratitis, the most common type, primarily involves Staphylococcus aureus and Pseudomonas aeruginosa. Timely diagnosis and treatment are crucial to prevent vision loss. Case Presentation: This case report presents a 78-year-old male patient with a burning sensation persisting for 1 week. The patient was diagnosed with keratitis caused by Arthrobacter, a Gram-positive coccobacillus commonly found in the environment. While the literature reports a few cases of Arthrobacter species keratitis, limited data exist regarding its clinical course and outcomes. Treatment with ciprofloxacin eye drops resulted in complete resolution of symptoms and a clear cornea upon final follow-up. Conclusion: Arthrobacter, a rare causative agent of keratitis, requires early suspicion for accurate diagnosis and treatment. Despite the limited literature on Arthrobacter keratitis, this case highlights the importance of considering uncommon pathogens in corneal infections. Further research is necessary to understand the prevalence and clinical course of Arthrobacter keratitis.

Soils and sediments from the Savannah River Site (SRS), located in the USA are known to have a long history of co-contamination with radionuclides (mainly uranium) and heavy metals. To better understand the bacterial taxonomic and genomic characteristic of the SRS soil habitat, shotgun metagenomes were obtained from three different levels of contaminated soil—high, medium, and low. Sequences were then assembled and annotated to generate metagenome-assembled genomes (MAGs) using toolkits within the nf-core/mag. The initial analysis resulted in a total of 254 MAGs. After bin refinement and de-replication, 55 MAGs which met the quality standard with a completeness > 75% and contamination < 25%, accounting for 21.67% of all the MAGs, were reconstructed. Further refinement with completeness > 90% and contamination < 10% yielded 24 MAGs (18 from the winter season and 6 from the summer season) spanning 6 bacterial phyla, predominantly Actinomycetota, Proteobacteriota, Bacteroidota, and Cyanobacteria. Overall, the Arthrobacter MAG was found to be robust for further analysis, with over 1749 genes putatively involved in the crucial metabolism of elements viz. nitrogen, phosphorous, and sulfur, and 598 genes encoding enzymes for the resistance of metals including cadmium, zinc, chromium, arsenic, and copper. In summary, this project enhances our understanding of genes conferring resistance to heavy metals in uranium-contaminated soils. [ABSTRACT FROM AUTHOR]

This research aims to study butanol fermentation from sweet sorghum stem juice (SSJ) by immobilized Clostridium beijerinckii TISTR 1461 cells on bamboo chopsticks using Arthrobacter sp. as an efficient bacterium for creating anaerobic conditions in scaled-up bioreactors. For batch culture in a 1-L screw-capped bottle, a butanol concentration (PB), butanol productivity (QB), and butanol yield (YB/S) were 12.09 g/L, 0.26 g/L·h and 0.28 g/g, respectively. These values were ~8 to 14% higher than those of a single culture using oxygen-free nitrogen (OFN) gas to generate anaerobic conditions. When butanol fermentation by the co-culture was scaled-up to 5-L and 30-L stirred-tank fermenters, the butanol production efficiency was not different from that using the 1-L bottles. Additionally, repeated-batch butanol fermentation in the 1-L bottles by the co-culture was successfully operated for four successive cycles with high butanol production. All results clearly indicate that Arthrobacter sp. is promising for creation of anaerobic conditions for butanol production by immobilized Clostridium in large scale bioreactors. [ABSTRACT FROM AUTHOR]

Desert soil hosts many microorganisms, whose activities are essential from an ecological viewpoint. Moreover, they are of great anthropic interest. The knowledge of extreme environments microbiomes may be beneficial for agriculture, technology, and human health. In this study, 11 Arthrobacter strains from topsoil samples collected from the Great Gobi A Strictly Protected Area in the Gobi Desert, were characterized by a combination of different techniques. The phylogenetic analysis, performed using their 16S rDNA sequences and the most similar Arthrobacter sequences found in databases, revealed that most of them were close to A. crystallopoietes, while others joined a sister group to the clade formed by A. humicola, A. pascens, and A. oryzae. The resistance of each strain to different antibiotics, heavy-metals, and NaCl was also tested as well as the inhibitory potential against human pathogens (i.e., Burkholderia ssp., Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus ssp.) via cross-streaking, to check the production of metabolites with antimicrobial activity. Data obtained revealed that all strains were resistant to heavy metals and were able to strongly interfere with the growth of many of the human pathogens tested. The volatile organic compounds (VOCs) profile of the 11 Arthrobacter strains was also analyzed. A total of 16 different metabolites were found, some of which were already known for having an inhibitory action against different Gram-positive and Gram-negative bacteria. Isolate MS-3A13, producing the highest quantity of VOCs, is the most efficient against Burkholderia cepacia complex (Bcc), K. pneumoniae, and coagulase-negative Staphylococci (CoNS) strains. This work highlights the importance of understanding microbial populations' phenotypical characteristics and dynamics in extreme environments to uncover the antimicrobial potential of new species and strains.

Long-term monitoring of microbial communities in the rhizosphere of post-fire forests is currently one of the key knowledge gaps. Knowing the time scale of the effects is indispensable to aiding post-fire recovery in vulnerable woodlands, including holm oak forests, that are subjected to a Mediterranean climate, as is the case with forests that are found in protected areas such as the Sierra Nevada National and Natural Park in southeastern Spain. We took rhizosphere soil samples from burned and unburned holm oak trees approximately 3, 6, and 9 years after the 2005 fire that devastated almost 3500 ha in southeastern Spain. We observed that the prokaryotic communities are recovering but have not yet reached the conditions observed in the unburned forest. A common denominator between this fire and other fires is the long-term persistence of three ecosystem recovery biomarkers—specifically, higher proportions of the genera Arthrobacter, Blastococcus, and Massilia in soil microbial communities after a forest fire. These pyrophilous microbes possess remarkable resilience against adverse conditions, exhibiting traits such as xerotolerance, nitrogen mineralization, degradation of aromatic compounds, and copiotrophy in favorable conditions. Furthermore, these biomarkers thrive in alkaline environments, which persist over the long term following forest fires. The relative abundance of these biomarkers showed a decreasing trend over time, but they were still far from the values of the control condition. In conclusion, a decade does not seem to be enough for the complete recovery of the prokaryotic communities in this Mediterranean ecosystem.

Bacterial strains of the genera Arthrobacter, Bacillus, Dietzia, Kocuria, and Micrococcus were isolated from oil-contaminated soils of the Balgimbaev, Dossor, and Zaburunye oil fields in Kazakhstan. They were selected from 1376 isolated strains based on their unique ability to use crude oil and polyaromatic hydrocarbons (PAHs) as sole source of carbon and energy in growth experiments. The isolated strains degraded a wide range of aliphatic and aromatic components from crude oil to generate a total of 170 acid metabolites. Eight metabolites were detected during the degradation of anthracene and of phenanthrene, two of which led to the description of a new degradation pathway. The selected bacterial strains Arthrobacter bussei/agilis SBUG 2290, Bacillus atrophaeus SBUG 2291, Bacillus subtilis SBUG 2285, Dietzia kunjamensis SBUG 2289, Kocuria rosea SBUG 2287, Kocuria polaris SBUG 2288, and Micrococcus luteus SBUG 2286 promoted the growth of barley shoots and roots in oil-contaminated soil, demonstrating the enormous potential of isolatable and cultivable soil bacteria in soil remediation. Key points: • Special powerful bacterial strains as potential crude oil and PAH degraders. • Growth on crude oil or PAHs as sole source of carbon and energy. • Bacterial support of barley growth as resource for soil remediation. [ABSTRACT FROM AUTHOR]

Transformation of 11-trifluoroacetate 6α-methylhydrocortisone (11-TFA MHC) by cells of the actinobacteria Arthrobacter (Nocardioides) was carried out in the presence of α-cyclodextrin (α-CD). The composition and dynamics of the accumulation of the transformation products in the culture medium at various pHs and the ratio of the α-CD/substrate were studied. It was shown that the addition of α-CD to the transformation medium at pH 7 promotes an increase in the rate of 1,2-dehydrogenation with the formation of 6 α-methylprednisolone 11-trifluoroacetate (11-TFA MPL). At pH 7, the primary process is the hydrolysis of the 11β-trifluoroacetyloxy group. In this case, the participation of α-CD in these processes as an acceptor of the trifluoroacetyl ion is not excluded. [ABSTRACT FROM AUTHOR]

Actinobacteria are an extremely diverse group of bacteria known for their ability to produce a range of biotechnologically relevant enzymes. Tunisian Forest ecosystems are relatively unexplored in terms of actinobacterial diversity and their enzyme activities, offering an excellent opportunity to isolate new potent actinobacterial strains that produce bioactive natural products. In this study, actinobaceria were isolated from soil samples collected from four forests in the Northern part of Tunisia, using Starch-casein media and characterized by morphological, molecular (16 S rRNA) and phenotypic (enzymatic activities) methods. Isolate's colonies showed a color ranging from whitish, brownish, yellow, green, black, pink-purple and orange, similar to actinobacterial morphology. Analysis of the 16 S rRNA gene sequences of the isolates showed that they belong to the phylum Actinobateria, Specifically the genera Streptomyces, Nocardioides, Arthrobacter, Kocuria and Paenarthrobacter genera with the prevalence of Streptomyces members such as S. albidochromogenes and S. neopeptinius. The analysis of enzymatic profiles, showed that actinobacterial isolates represent a promising source of enzymes with potential biotechnological applications including amylases, CMCase, pectinases, xylanases and laccases. [ABSTRACT FROM AUTHOR]

The application of biostimulants has been proven to be an advantageous tool and an appropriate form of management towards the effective use of natural resources, food security, and the beneficial effects on plant growth and yield. Plant-growth-promoting rhizobacteria (PGPR) are microbes connected with plant roots that can increase plant growth by different methods such as producing plant hormones and molecules to improve plant growth or providing increased mineral nutrition. They can colonize all ecological niches of roots to all stages of crop development, and they can affect plant growth and development directly by modulating plant hormone levels and enhancing nutrient acquisition such as of potassium, phosphorus, nitrogen, and essential minerals, or indirectly via reducing the inhibitory impacts of different pathogens in the forms of biocontrol parameters. Many plant-associated species such as Pseudomonas, Acinetobacter, Streptomyces, Serratia, Arthrobacter, and Rhodococcus can increase plant growth by improving plant disease resistance, synthesizing growth-stimulating plant hormones, and suppressing pathogenic microorganisms. The application of biostimulants is both an environmentally friendly practice and a promising method that can enhance the sustainability of horticultural and agricultural production systems as well as promote the quantity and quality of foods. They can also reduce the global dependence on hazardous agricultural chemicals. Science Direct, Google Scholar, Springer Link, CAB Direct, Scopus, Springer Link, Taylor and Francis, Web of Science, and Wiley Online Library were checked, and the search was conducted on all manuscript sections in accordance with the terms Acinetobacter, Arthrobacter, Enterobacter, Ochrobactrum, Pseudomonas, Rhodococcus, Serratia, Streptomyces, Biostimulants, Plant growth promoting rhizobactera, and Stenotrophomonas. The aim of this manuscript is to survey the effects of plant-growth-promoting rhizobacteria by presenting case studies and successful paradigms in various agricultural and horticultural crops. [ABSTRACT FROM AUTHOR]

Arthrobacter sp. EM1 is a cold-adapted bacterium isolated from the Antarctic region, which was known to exhibit mannan-degrading activity. Accordingly, this strain not only promises a cell factory for mannan-degrading enzymes, widely used in industry but also serves as a model organism to decipher its cold adaptation mechanism. Accordingly, whole genome sequencing of the EM1 strain was performed via Single Molecule Real Time sequencing under the PacBio platform, followed by genome HGAP de novo assembly and genome annotation through Rapid Annotation System Technology (RAST) server. The chromosome of this strain is 3,885,750 bp in size with a GC content of 65.8. The annotation predicted a total of 3607 protein-coding genes and 65 RNA genes, which were classified under 398 subsystems. The subsystem with the highest number of genes is carbohydrate metabolism (397 genes), which includes two genes encoding mannan-degrading enzymes (endoglucanase and α-mannosidase). This confirmed that the EM1 strain is able to produce cold-adapted mannan degrading enzymes. The complete genome sequence data have been submitted to the National Center for Biotechnology Information (NCBI) and have been deposited at GenBank (Bioproject ID Accession Number: PRJNA963062; Biosample ID Accession Number: SAMN34434776; GenBank: CP124836.1; https://www.ncbi.nlm.nih.gov/nuccore/CP124836).

ABSTRACT Volatile organic compounds (VOCs) produced by plant-associated microorganisms could serve as natural biocontrol compounds. In this work, we investigate the potential of wheat rhizosphere Microbacterium and Arthrobacter actinomycetes to inhibit the growth of major wheat phytopathogenic fungi, Fusarium graminearum and Zymoseptoria tritici via production of antifungal VOCs. A correlative analysis between fungal-growth inhibition versus bacterial volatilomic profiles identified four dimethylpolysulfide (DMPS) VOCs as the main active compounds behind their biocontrol potential. Subsequent inhibition assays reveal that DMTriS (dimethyltrisulfide) exhibits the strongest inhibition effects, then dimethyldisulfide (DMDiS). Further investigation focuses on the mechanisms behind F. graminearum-growth inhibition by the most active strain Microbacterium JM188 in dual culture. Surprisingly, nine interaction-induced VOCs, including two fungal sesquiterpenes, were exclusively detected in dual cultures, suggesting a complex interplay between microbial VOC production and sensing. More importantly, all JM188 VOCs, including antifungal DMPS, were less abundant in dual cultures, suggesting an uptake of bacterial VOCs by the fungus. Quantification of pure DMPS after confrontation with F. graminearum confirmed complete and partial uptake by the fungus of DMTriS and DMDiS VOCs, respectively, suggesting a potential link between the fungal uptake level of bacterial VOCs and their toxicity. Finally, we demonstrated that F. graminearum growth inhibition leads to a complete depletion of DON (deoxynivalenol) carcinogenic mycotoxins, highlighting a significant modulation of fungal metabolism. Collectively, these results pinpoint DMPS as broad-range fungal-inhibiting VOCs produced by rhizosphere Microbacterium and Arthrobacter, and emphasize the extensive VOC-mediated interplay between bacterial biocontrol agents and fungal pathogens. IMPORTANCE As the management of wheat fungal diseases becomes increasingly challenging, the use of bacterial agents with biocontrol potential against the two major wheat phytopathogens, Fusarium graminearum and Zymoseptoria tritici, may prove to be an interesting alternative to conventional pest management. Here, we have shown that dimethylpolysulfide volatiles are ubiquitously and predominantly produced by wheat-associated Microbacterium and Arthrobacter actinomycetes, displaying antifungal activity against both pathogens. By limiting pathogen growth and DON virulence factor production, the use of such DMPS-producing strains as soil biocontrol inoculants could limit the supply of pathogen inocula in soil and plant residues, providing an attractive alternative to dimethyldisulfide fumigant, which has many non-targeted toxicities. Notably, this study demonstrates the importance of bacterial volatile organic compound uptake by inhibited F. graminearum, providing new insights for the study of volatiles-mediated toxicity mechanisms within bacteria-fungus signaling crosstalk.

Disease suppressive composts are known, yet little information on the potential role of specific microbial antagonist within are available. Arthrobacter humicola isolate M9-1A has been obtained from a compost prepared from marine residues and peat moss. The bacterium is a non-filamentous actinomycete with antagonistic activity against plant pathogenic fungi and oomycetes sharing its ecological niche in agri-food microecosystems. Our objective was to identify and characterize compounds with antifungal activity produced by A. humicola M9-1A. Arthrobacter humicola culture filtrates were tested for antifungal activity in vitro and in vivo and a bioassay-guided approach was used to identify potential chemical determinants of its observed activity against molds. The filtrates reduced the development of lesions of Alternaria rot on tomatoes and the ethyl acetate extract inhibited growth of Alternaria alternata. A compound, arthropeptide B [cyclo-(L-Leu, L-Phe, L-Ala, L-Tyr)], was purified from the ethyl acetate extract of the bacterium. Arthropeptide B is a new chemical structure reported for the first time and has shown antifungal activity against A. alternata spore germination and mycelial growth. [ABSTRACT FROM AUTHOR]

Early blight of tomato caused by Alternaria solani results in significant crop losses. In this study, Bacillus subtilis J3 and Pseudomonas fluorescens J8 were co-cultured as a synthetic microbial community (BCA) for synergistic biocontrol of A. solani, and the inhibition mechanism was investigated. BCA presented an inhibition ration against A. solani at 94.91%, which lowered the disease incidence by 38.26–42.87%; reduced peroxidase, catalase, superoxide dismutase activity of tomatoes by 73.11–90.22%; and promoted the biomass by 66.91–489.21%. With BCA protection, the relative expression of tomato resistance genes (including gPAL2, SWRKY, PR-10, and CHI) in roots and leaves was 12.83–90.70% lower than without protection. BCA also significantly altered the rhizosphere and phyllosphere microbial community. The abundance of potentially beneficial bacteria, including Bacillus, Pseudomonas, Arthrobacter, Lysobacter, and Rhizobium, elevated by 6.58–192.77%. They were negatively correlated with resistance gene expression, indicating their vital involvement in disease control. These results provided essential information on the synergistic biocontrol mechanism of bacteria against pathogens, which could contribute to developing novel biocontrol strategies. Key points: • Bacillus and Pseudomonas present a synergistic biocontrol effect against A. solani. • Biocontrol prevents pathogen damage and improves tomato growth and systemic resistance. • Beneficial bacteria thrive in the rhizosphere is the key to microbial regulation. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of some adaptive properties of a bacterial isolate from wheat bran, identified by the 16S rRNA gene as an Arthrobacter agilis strain. According to the literature data, A. agilis does not belong to the dominant bacterial species of wheat microbial associations and activates growth at low ambient temperatures. The studied A. agilis strain showed poor growth in a microbial consortium when an aqueous suspension of wheat bran, partially fermented at 28 ± 1°C by the native microbiota, was plated on a dense MPA medium and produced the pigment after three weeks of storage at 4 ± 1°C. Moderate growth of bacteria without increased pigmentation was observed during its subsequent transfer after low-temperature storage on agar media containing carbohydrates and nitrogen compounds, mineral salts, and vitamins that were more easily utilized than native bran. The growth of colonies upon plating on such media increased in the series: thermally fermented wheat bran → HMF agar → LB (without salt). It was revealed that the A. agilis strain, which was not typical of the wheat bran microflora, under the influence of osmotic and/or temperature shock (in response to a sharp change in the NaCl concentration and/or a difference in ambient temperatures) produced pigments both in agar and liquid cultures. According to the results of spectral analysis, the pigment was assigned to carotenoids and tentatively identified as bacterioruberin. Quantitative evaluation showed that, under stress conditions during submerged cultivation, the studied strain A. agilis wb28 was able to synthesize the pigment at the level of 52.8 mg/L (17.2 mg/g biomass). [ABSTRACT FROM AUTHOR]

The PAH degrading microbial consortium was collected from sodic soil of the nursery of Guru Jambheshwar University of Science and Technology, Hisar, Haryana (India). And the soil was artificially amended with phenanthrene and naphthalene to isolate the PAHs degrading microbial consortium. The diversity of microbial consortium was analyzed using the NGS (Next Generation Sequencing) based metagenomic approach. The result of diversity analysis showed species Tepidanaerobacter syntrophicus, Sphingomonas oliophenolica, Arthrobacter psychrochitinipnius, Bifidobacterium bombi, Nocardiodies islandensis, Rhodovibrio sodomensis, Thiorhodococus pfennigii, Aeromicrobium ponti, Steroidobacter dentrificans, Actinomaduria maheshkhaliensis, Dactylosporangium maewongense, Pelotomaculum isophthalicicum, and Nocardioides islandensis were present in the consortium. Moreover, Sphingomonas, Arthrobacter, Sphingobium, Azospirillium, Thirohodococcus, and Pelotomaculum were the prominent pollutant degrader genera in the microbial consortium. Since the bioremediation of these pollutants occurs with a significant reduction in toxicity, the study's perspective is to use this type of consortium for bioremediation of specifically contaminated soil. The present work's novelty was to find the helpful microbial consortium for the bioremediation of toxic compounds such as naphthalene and phenanthrene. In this study, the degradation of such compounds was done by the various communities of genera like Bifidobacterium, Conexibacter, Sterodobacter, Rhodovibrio, Arthrobacter, Actinomadura, and Euzebya, which are rarely described in the earlier researches. Therefore, this study will enhance the quality of future research. [ABSTRACT FROM AUTHOR]

The effect of wheat and maize rotations and the application of plant-animal compost on potato bacterial wilt and yield was investigated. The proposed method was tested in three separate locations, each two acres in size, with an untreated control. The first two were naturally infested, but the third was pathogen-free. Infested locations that had been treated experienced a significant reduction in disease incidence. The addition of a bio-fertilizer mixture (Azotobacter sp., Azospirillum sp., Bacillus megaterium, and Bacillus circulans) improved the compost's suppressive potential. The method increased soil organic matter (SOM), N, P, K, Ca+2, and Mg+2 while decreasing Na+ levels and increasing potato yield. The relative abundance of Ralstonia decreased while that of Arthrobacter, Streptomyces, and Nocardioides increased. The presence of Gracilibacillus, Cellvibrio, Bacillus, and Paenibacillus was associated with a decrease in Ralstonia, whereas the presence of Propionibacterium (a nitrogen-fixing bacteria) was associated with an increase in Ralstonia. [ABSTRACT FROM AUTHOR]

Superoxide and other reactive oxygen species (ROS) shape microbial communities and drive the transformation of metals and inorganic/organic matter. Taxonomically diverse bacteria and phytoplankton produce extracellular superoxide during laboratory cultivation. Understanding the physiological reasons for extracellular superoxide production by aerobes in the environment is a crucial question yet not fully solved. Here, we showed that iron-starving Arthrobacter sp. QXT-31 (A. QXT-31) secreted a type of siderophore [deferoxamine (DFO)], which provoked extracellular superoxide production by A. QXT-31 during carbon sources-level fluctuation. Several other siderophores also demonstrated similar effects to A. QXT-31. RNA-Seq data hinted that DFO stripped iron from iron-bearing proteins in electron transfer chain (ETC) of metabolically active A. QXT-31, resulting in electron leakage from the electron-rich (resulting from carbon sources metabolism by A. QXT-31) ETC and superoxide production. Considering that most aerobes secrete siderophore(s) and undergo carbon sources-level fluctuation, the superoxide-generation pathway is likely a common pathway by which aerobes produce extracellular superoxide in the environment, thus influencing the microbial community and cycling of elements. Our results pointed that the ubiquitous siderophore might be the potential driving force for the microbial generation of superoxide and other ROS and revealed the important role of iron physiology in microbial ROS generation.

Bacteriophages exhibit a vast spectrum of relatedness and there is increasing evidence of close genomic relationships independent of host genus. The variability in phage similarity at the nucleotide, amino acid, and gene content levels confounds attempts at quantifying phage relatedness, especially as more novel phages are isolated. This study describes three highly similar novel Arthrobacter globiformis phages-Powerpuff, Lego, and YesChef-which were assigned to Cluster AZ using a nucleotide-based clustering parameter. Phages in Cluster AZ, Microbacterium Cluster EH, and the former Microbacterium singleton Zeta1847 exhibited low nucleotide similarity. However, their gene content similarity was in excess of the recently adopted Microbacterium clustering parameter, which ultimately resulted in the reassignment of Zeta1847 to Cluster EH. This finding further highlights the importance of using multiple metrics to capture phage relatedness. Additionally, Clusters AZ and EH phages encode a shared integrase indicative of a lysogenic life cycle. In the first experimental verification of a Cluster AZ phage's life cycle, we show that phage Powerpuff is a true temperate phage. It forms stable lysogens that exhibit immunity to superinfection by related phages, despite lacking identifiable repressors typically required for lysogenic maintenance and superinfection immunity. The ability of phage Powerpuff to undergo and maintain lysogeny suggests that other closely related phages may be temperate as well. Our findings provide additional evidence of significant shared phage genomic content spanning multiple actinobacterial host genera and demonstrate the continued need for verification and characterization of life cycles in newly isolated phages.

Endosulfan is an organochlorine insecticide widely used for agricultural pest control. Many nations worldwide have restricted or completely banned it due to its extreme toxicity to fish and aquatic invertebrates. Arthrobacter sp. strain KW has the ability to degrade α, β endosulfan and its intermediate metabolite endosulfate; this degradation is associated with Ese protein, a two‐component flavin‐dependent monooxygenase (TC‐FDM). Employing in silico tools, we obtained the 3D model of Ese protein, and our results suggest that it belongs to the Luciferase Like Monooxygenase family (LLM). Docking studies showed that the residues V59, V315, D316, and T335 interact with α‐endosulfan. The residues: V59, T60, V315, D316, and T335 are implicated in the interacting site with β‐endosulfan, and the residues: H17, V315, D316, T335, N364, and Q363 participate in the interaction with endosulfate. Topological analysis of the electron density by means of the Quantum Theory of Atoms in Molecules (QTAIM) and the Non‐Covalent Interaction (NCI) index reveals that the Ese‐ligands complexes are formed mainly by dispersive forces, where Cl atoms have a predominant role. As Ese is a monooxygenase member, we predict the homodimer formation. However, enzymatic studies must be developed to investigate the Ese protein's enzymatic and catalytic activity. [ABSTRACT FROM AUTHOR]

Desert soil hosts many microorganisms, whose activities are essential from an ecological viewpoint. Moreover, they are of great anthropic interest. The knowledge of extreme environments microbiomes may be beneficial for agriculture, technology, and human health. In this study, 11 Arthrobacter strains from topsoil samples collected from the Great Gobi A Strictly Protected Area in the Gobi Desert, were characterized by a combination of different techniques. The phylogenetic analysis, performed using their 16S rDNA sequences and the most similar Arthrobacter sequences found in databases, revealed that most of them were close to A. crystallopoietes, while others joined a sister group to the clade formed by A. humicola, A. pascens, and A. oryzae. The resistance of each strain to different antibiotics, heavy-metals, and NaCl was also tested as well as the inhibitory potential against human pathogens (i.e., Burkholderia ssp., Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus ssp.) via cross-streaking, to check the production of metabolites with antimicrobial activity. Data obtained revealed that all strains were resistant to heavy metals and were able to strongly interfere with the growth of many of the human pathogens tested. The volatile organic compounds (VOCs) profile of the 11 Arthrobacter strains was also analyzed. A total of 16 different metabolites were found, some of which were already known for having an inhibitory action against different Grampositive and Gram-negative bacteria. Isolate MS-3A13, producing the highest quantity of VOCs, is the most efficient against Burkholderia cepacia complex (Bcc), K. pneumoniae, and coagulase-negative Staphylococci (CoNS) strains. This work highlights the importance of understanding microbial populations' phenotypical characteristics and dynamics in extreme environments to uncover the antimicrobial potential of new species and strains. [ABSTRACT FROM AUTHOR]

The application of biostimulants has been proven to be an advantageous tool and an appropriate form of management towards the effective use of natural resources, food security, and the beneficial effects on plant growth and yield. Plant-growth-promoting rhizobacteria (PGPR) are microbes connected with plant roots that can increase plant growth by different methods such as producing plant hormones and molecules to improve plant growth or providing increased mineral nutrition. They can colonize all ecological niches of roots to all stages of crop development, and they can affect plant growth and development directly by modulating plant hormone levels and enhancing nutrient acquisition such as of potassium, phosphorus, nitrogen, and essential minerals, or indirectly via reducing the inhibitory impacts of different pathogens in the forms of biocontrol parameters. Many plant-associated species such as Pseudomonas, Acinetobacter, Streptomyces, Serratia, Arthrobacter, and Rhodococcus can increase plant growth by improving plant disease resistance, synthesizing growth-stimulating plant hormones, and suppressing pathogenic microorganisms. The application of biostimulants is both an environmentally friendly practice and a promising method that can enhance the sustainability of horticultural and agricultural production systems as well as promote the quantity and quality of foods. They can also reduce the global dependence on hazardous agricultural chemicals. Science Direct, Google Scholar, Springer Link, CAB Direct, Scopus, Springer Link, Taylor and Francis, Web of Science, and Wiley Online Library were checked, and the search was conducted on all manuscript sections in accordance with the terms Acinetobacter, Arthrobacter, Enterobacter, Ochrobactrum, Pseudomonas, Rhodococcus, Serratia, Streptomyces, Biostimulants, Plant growth promoting rhizobactera, and Stenotrophomonas. The aim of this manuscript is to survey the effects of plant-growth-promoting rhizobacteria by presenting case studies and successful paradigms in various agricultural and horticultural crops.

Antimicrobial peptides (AMPs) are naturally occurring molecules found in various organisms that can help to defend against invading microorganisms and reduce the likelihood of drug resistance development. This study focused on the isolation of new AMPs from the genome library of a Gram-positive bacterium called Arthrobacter sp. H5. To achieve this, we used the Bacillus subtilis expression system and employed bioinformatics techniques to optimize and modify the peptides, resulting in the development of a new synthetic antimicrobial peptide (SAMP). Ap920 is expected to be a new antimicrobial peptide with a high positive charge (+12.5). Through optimization, a new synthetic antimicrobial peptide, Ap920-WI, containing only 15 amino acids, was created. Thereafter, the antimicrobial and antifungal activities of Ap920-WI were determined using minimum inhibitory concentration (MIC) and the concentration for 50% of maximal effect (EC50). The Ap920-WI peptide was observed to target the outer membrane of fungal hyphae, leading to inhibition of growth in Rhizoctonia Solani, Sclerotinia sclerotiorum, and Botrytis cinerea. In plants, Ap920-WI showed significant antifungal activity and inhibited the infestation of S. sclerotiorum on rape leaves. Importantly, Ap920-WI was found to be safe for mammalian cells since it did not show any hemolytic activity against sheep red blood cells. Overall, the study found that the new synthetic antimicrobial peptide Ap920-WI exhibits broad-spectrum activity against microorganisms and may offer a new solution for controlling plant diseases, as well as hold potential for drug development. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. PHBs are the most promising type of bioplastic; they are nontoxic, biodegradable and biocompatible and have properties similar to those of conventional plastics. In the present study, an attempt was made to screen of different bacterial isolates accumulating PHB from soil samples collected from Istanbul, Turkey. A total of 86 different bacterial isolates were isolated from soil samples and a total of 32 isolates were suggested to be PHB producer when stained with Sudan Black B, a preliminary screening agent for lipophilic compounds. 13 bacterial isolates were selected as PHB producing isolates by using the Nile blue A dying technique. 16S rRNA gene sequences analysis showed that PHB producing 13 isolates belonged to Pseudomonas, Arthrobacter and Bacillus genera. The PHB from the isolates was extracted using the dispersion method of the hypochlorite and chloroform method. The highest PHB production and percentage productivity were obtained from Pseudomonas plecoglossicida M9 (0.94 PHB g/L; 78.8% PHB) and Pseudomonas baetica Y6 (0.81 PHB g/L; 74.3% PHB) respectively. [ABSTRACT FROM AUTHOR]

Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline environments are promising candidates for the recovery of useful biomaterials including polyhydroxyalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegradable, biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospection of bacteria isolated from hypersaline-alkaliphilic lakes in Kenya for the potential production of PHAs. In the present study, 218 isolates were screened by Sudan Black B and Nile Red A staining. Of these isolates, 31 were positive for PHA production and were characterized using morphological, biochemical, and molecular methods. Through 16S rRNA sequencing, we found that the isolates belonged to the genera Arthrobacter spp., Bacillus spp., Exiguobacterium spp., Halomonas spp., Paracoccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023 isolated from Lake Magadi had the highest PHA accumulation ability, with an initial biomass-to-PHA conversion rate of 19.14% on a 2% glucose substrate. Under optimized fermentation conditions, MO22 had a maximum PHA concentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9% PHA conversion, equivalent to a PHA yield of 0.02 g/g of biomass. The optimal PHA production media had an initial pH of 9.0, temperature of 35 °C, salinity of 3%, and an incubation period of 48 h with 2.5% sucrose and 0.1% peptone as carbon and nitrogen sources, respectively. This study suggests that bacteria isolated from hypersaline and alkaliphilic tropical lakes are promising candidates for the production of polyhydroxyalkanoates. [ABSTRACT FROM AUTHOR]

Uricase (or Urate oxidase), a key enzyme involved in purine metabolism, is commonly used in treating conditions such as gout, hyperuricemia, and tumor lysis syndrome. In this study, a uricase-producing strain (named CSAJ-16) was isolated from the soil sample of Cangshan Mountain, Yunnan Province, China. This strain was identified as Arthrobacter sp. CSAJ-16. Based on the gene sequence alignment, the uricase gene (named aruox) of Arthrobacter sp. CSAJ-16 was amplified and heterologously expressed. The recombinant uricase (ArUOX) was about 32 kDa. The optimal pH and temperature of ArUOX were pH 7 and 20°C, respectively. The ArUOX remained above 50% relative activity after incubation at 37°C for 100 min or at pH 6.0–8.6 for 24 h. Moreover, metal ions such as K+, Mg2+, Ca2+, Ba2+ and Pb2+ can significantly enhance the activity of ArUOX (> 200%). These enzymatic properties indicate that ArUOX has potential applications in pharmaceutical enzymes and uric acid detection kits. [ABSTRACT FROM AUTHOR]

Arthrobacter is a coryneform bacterium in the family of Micrococcaceae. Arthrobacter species isolated from hostile environments are capable of producing interesting bioactive compounds, some of which may be a new class of antibiotics. Here, we present the complete genome sequence of Arthrobacter sp. ES1 isolated from Schirmacher Oasis in East Antarctica. Genomic DNA sequencing was performed using the Illumina MiSeq sequencer. Arthrobacter sp. ES1 has a genome size of 3,964,927 bp and a GC content of 65.73%. The raw genome sequences have been deposited in the NCBI Sequence Read Archive database under the accession number, SRR20664316.

Bacteriophages (phages) exhibit high genetic diversity, and the mosaic nature of the shared genetic pool makes quantifying phage relatedness a shifting target. Early parameters for clustering of related Mycobacteria and Arthrobacter phage genomes relied on nucleotide identity thresholds but, more recently, clustering of Gordonia and Microbacterium phages has been performed according to shared gene content. Singleton phages lack the nucleotide identity and/or shared gene content required for clustering newly sequenced genomes with known phages. Whole genome metrics of novel Arthrobacter phage BlueFeather, originally designated a putative singleton, showed low nucleotide identity but high amino acid and gene content similarity with Arthrobacter phages originally assigned to Clusters FE and FI. Gene content similarity revealed that BlueFeather shared genes with these phages in excess of the parameter for clustering Gordonia and Microbacterium phages. Single gene analyses revealed evidence of horizontal gene transfer between BlueFeather and phages in unique clusters that infect a variety of bacterial hosts. Our findings highlight the advantage of using shared gene content to study seemingly genetically isolated phages and have resulted in the reclustering of BlueFeather, a putative singleton, as well as former Cluster FI phages, into a newly expanded Cluster FE.

Medicinal plants play an important role in the discovery of new bioactive compounds with antimicrobial activity, thanks to their pharmacological properties. However, members of their microbiota can also synthesize bioactive molecules. Among these, strains belonging to the genera Arthrobacter are commonly found associated with the plant's microenvironments, showing plant growth-promoting (PGP) activity and bioremediation properties. However, their role as antimicrobial secondary metabolite producers has not been fully explored. The aim of this work was to characterize the Arthrobacter sp. OVS8 endophytic strain, isolated from the medicinal plant Origanum vulgare L., from molecular and phenotypic viewpoints to evaluate its adaptation and influence on the plant internal microenvironments and its potential as a producer of antibacterial volatile molecules (VOCs). Results obtained from the phenotypic and genomic characterization highlight its ability to produce volatile antimicrobials effective against multidrug-resistant (MDR) human pathogens and its putative PGP role as a producer of siderophores and degrader of organic and inorganic pollutants. The outcomes presented in this work identify Arthrobacter sp. OVS8 as an excellent starting point toward the exploitation of bacterial endophytes as antibiotics sources. [ABSTRACT FROM AUTHOR]

A novel bacterium, Arthrobacter globiformis DC-1, capable of degrading DDT as its sole carbon and energy source, was isolated from DDT-contaminated agricultural soil. The bacterium can degrade up to 76.3% of the DDT at a concentration of 10 mg/L in the mineral salt medium (MSM) within 1 day of incubation. The effects of various environmental conditions, such as the concentration of DDT, temperature, pH and additional carbon sources, on its growth and biodegrading capacity of DDT were investigated in the MSM. The A. globiformis DC-1 strain could efficiently grow and degrade DDT at a wide range of concentrations, with the maximum growth and degradation rate at 10 mg/LDDT, followed by inhibitory effects at higher concentrations (20 and 30 mg/LDDT). Mesophilic temperatures (25–30 °C) and a pH of 7–7.5 were the most suitable conditions for the growth and biodegradation. The presence of carbon sources significantly increased the growth of the DC-1 strain; however, degradation was inhibited in the present of glucose, sucrose and fructose, and peptone was determined to be the most appropriate carbon source for A. globiformis DC-1. The optimal DDT degradation (84.2%) was observed at 10 mg/LDDT, peptone as carbon source in pH 7.5 at 30 °C with 1 day of incubation. This strain could also degrade DDE, DDD and DDT simultaneously as the sole carbon and energy source, with degradation rates reaching 70.61%, 64.43% and 60.24% in 10 days, respectively. The biodegradation pathway by A. globiformis DC-1 revealed that DDT was converted to DDD and DDE via dechlorination and dehydrochlorination, respectively; subsequently, both DDD and DDE transformed to DDMU through further dechlorination, and finally, after ring opening, DDMU was mineralized to carbon dioxide. No intermediate metabolites accumulation was observed during the GC/MS analysis, demonstrating that the A. globiformis DC-1 strain can be used for the bioremediation of DDT residues in the environment. [ABSTRACT FROM AUTHOR]

A novel virus lytic for Pseudomonas aeruginosa has been purified. Its viral particles have a siphoviral morphology with a head 60 nm in diameter and a noncontractile tail 184 nm long. The dsDNA genome consists of 16,449 bp, has cohesive 3′ termini, and encodes 28 putative proteins in a single strain. The peptidoglycan endopeptidase encoded by ORF 16 was found to be the lytic enzyme of this virus. The recombinant, purified enzyme was active up to 55 °C in the pH range 6–9 against all tested isolates of P. aeruginosa, but, surprisingly, also against the distant Gram-positive micrococci Arthrobacter globiformis and A. pascens. Both this virus and its endolysin are further candidates for possible treatment against P. aeruginosa and probably also other bacteria. [ABSTRACT FROM AUTHOR]

Bacterioruberin and its rare glycosylated derivatives are produced by Arthrobacter agilis as an adaptation strategy to low temperature conditions. The high antioxidant properties of bacterioruberin held great promise for different future applications like the pharmaceutical and food industries. Microbial production of bacterioruberin via a cost-effective medium will help increase its commercial availability and industrial use. The presented study aims to optimize the production of the rare C50 carotenoid bacterioruberin and its derivatives from the psychotrophic bacteria Arthrobacter agilis NP20 strain on a whey-based medium as a cost effective and readily available nutritious substrate. The aim of the study is extended to assess the efficiency of whey treatment in terms of estimating total nitrogen content in treated and untreated whey samples. The significance of medium ingredients on process outcome was first tested individually; then the most promising factors were further optimized using Box Behnken design (BBD). The produced carotenoids were characterized using UV–visible spectroscopy, FTIR spectroscopy, HPLC–DAD chromatography and HPLC-APCI-MS spectrometry. The maximum pigment yield (5.13 mg/L) was achieved after a 72-h incubation period on a core medium composed of 96% sweet whey supplemented with 0.46% MgSO4 & 0.5% yeast extract and inoculated with 6% (v/v) of a 24 h pre-culture (109 CFU/mL). The cost of the formulated medium was 1.58 $/L compared with 30.1 $/L of Bacto marine broth medium. The extracted carotenoids were identified as bacterioruberin, bis-anhydrobacteriouberin, mono anhydrobacterioruberin, and glycosylated bacterioruberin. The presented work illustrates the possibility of producing bacterioruberin carotenoid from Arthrobacter agilis through a cost-effective and eco-friendly approach using cheese whey-based medium. [ABSTRACT FROM AUTHOR]

The role of microbial interactions and the underlying mechanisms that shape complex biofilm communities are poorly understood. Here we employ a microfluidic chip to represent porous subsurface environments and show that cooperative microbial interactions between free-living and biofilm-forming bacteria trigger active spatial segregation to promote their respective dominance in segregated microhabitats. During initial colonization, free-living and biofilm-forming microbes are segregated from the mixed planktonic inoculum to occupy the ambient fluid and grain surface. Contrary to spatial exclusion through competition, the active spatial segregation is induced by cooperative interactions which improves the fitness of both biofilm and planktonic populations. We further show that free-living Arthrobacter induces the surface colonization by scavenging the biofilm inhibitor, D-amino acids and receives benefits from the public goods secreted by the biofilm-forming strains. Collectively, our results reveal how cooperative microbial interactions may contribute to microbial coexistence in segregated microhabitats and drive subsurface biofilm community succession. Cooperative interactions might be important in spatially structured microbial habitats. Here, the authors show that cooperative interactions between planktonic and biofilm-forming bacteria drive spatial segregation, and thereby enable species' coexistence, in a microfluidic chip environment. [ABSTRACT FROM AUTHOR]

According to average nucleotide identity (ANI) analysis of the complete genomes, strain 24S4–2 isolated from Antarctica is considered as a potential novel Arthrobacter species. Arthrobacter sp. 24S4–2 could grow and produce ammonium in nitrate or nitrite or even nitrogen free medium. Strain 24S4–2 was discovered to accumulate nitrate/nitrite and subsequently convert nitrate to nitrite intracellularly when incubated in a nitrate/nitrite medium. In nitrogen-free medium, strain 24S4–2 not only reduced the accumulated nitrite for growth, but also secreted ammonia to the extracellular under aerobic condition, which was thought to be linked to nitrite reductase genes nirB, nirD, and nasA by the transcriptome and RT-qPCR analysis. A membrane-like vesicle structure was detected in the cell of strain 24S4–2 by transmission electron microscopy, which was thought to be the site of intracellular nitrogen supply accumulation and conversion. This spatial and temporal conversion process of nitrogen source helps the strain maintain development in the absence of nitrogen supply or a harsh environment, which is part of its adaption strategy to the Antarctic environment. This process may also play an important ecological role, that other bacteria in the environment would benefit from its extracellular nitrogen source secretion and nitrite consumption characteristics.

As an indispensable enzyme for the hydrolysis of dextran, dextranase has been widely used in the fields of food and medicine. It should be noted that the weak thermostability of dextranase has become a restricted factor for industrial applications. This study aims to improve the thermostability of dextranase AoDex in glycoside hydrolase (GH) family 49 that derived from Arthrobacter oxydans KQ11. Some mutants were predicted and constructed based on B-factor analysis, PoPMuSiC and HotMuSiC algorithms, and four mutants exhibited higher heat resistance. Compared with the wild-type, mutant S357P showed the best improved thermostability with a 5.4-fold increase of half-life at 60 °C, and a 2.1-fold increase of half-life at 65 °C. Furthermore, S357V displayed the most obvious increase in enzymatic activity and thermostability simultaneously. Structural modeling analysis indicated that the improved thermostability of mutants might be attributed to the introduction of proline and hydrophobic effects, which generated the rigid optimization of the structural conformation. These results illustrated that it was effective to improve the thermostability of dextranase AoDex by rational design and site-directed mutagenesis. The thermostable mutant of dextranase AoDex has potential application value, and it can also provide references for engineering other thermostable dextranases of the GH49 family. [ABSTRACT FROM AUTHOR]

Plants Nicotiana tabacum L. with the choline oxidase gene (codA) responsible for the synthesis of glycine-betaine by agrobacterial transformation were obtained. In order to identify possible environmental consequences during the cultivation of transformants, microbial complexes in the rhizosphere were studied. Soil actinomycetes were used as a bioindication group of microorganisms. The abundance, taxonomic composition, and functional structure of the rhizosphere complexes of the original Samsun variety and independent transgenic lines CodA7 and CodA17 with the different codA gene were expressed. There were no significant differences in the taxonomic structure or the occurrence of phytopathogenic fungal antagonists or cellulolytic agents in the rhizosphere of the original plants and transformants. The structure of actinomycete complexes of transformants was characterized by variability comparable in magnitude with variability due to the stress effect of the soil background. [ABSTRACT FROM AUTHOR]

A newly isolated cadmium (Cd)-resistant bacterial strain from herbicides-polluted soil in China could use atrazine as the sole carbon, nitrogen, and energy source for growth in a mineral salt medium (MSM). Based on 16S rRNA gene sequence analysis and physiochemical tests, the bacterium was identified as Arthrobacter sp. and named ST11. The biodegradation of atrazine by ST11 was investigated in experiments, with the compound present either as crystals or dissolved in di(2-ethylhexyl) phthalate (DEHP) as a non-aqueous phase liquid (NAPL). After 48 h, ST11 consumed 68% of the crystalline atrazine in MSM. After being dissolved in DEHP, the degradation ratio of atrazine was reduced to 55% under the same conditions. Obviously, the NAPL-dissolved atrazine has lower bioavailability than the crystalline atrazine. Cd2+ at concentrations of 0.05–1.5 mmol/L either had no effect (<0.3 mmol/L), slight effects (0.5–1.0 mmol/L), or significantly (1.5 mmol/L) inhibited the growth of ST11 in Luria-Bertani medium. Correspondingly, in the whole concentration range (0.05–1.5 mmol/L), Cd2+ promoted ST11 to degrade atrazine, whether crystalline or dissolved in DEHP. Refusal to adsorb Cd2+ may be the main mechanism of high Cd resistance in ST11 cells. These results may provide valuable insights for the microbial treatment of arable soil co-polluted by atrazine and Cd. [ABSTRACT FROM AUTHOR]

Cold habitat is considered a potential source for detergent industry enzymes. This study aims at the metagenomic investigation of Tsomgo lake for taxonomic and functional annotation, unveiling the deterzome potential of the residing microbiota at this site. The present investigation revealed molecular profiling of microbial community structure and functional potential of the high-altitude Tsomgo lake samples of two different temperatures, harvested during March and August. Bacteria were found to be the most dominant phyla, with traces of genomic pieces of evidence belonging to archaea, viruses, and eukaryotes. Proteobacteria and Actinobacteria were noted to be the most abundant bacterial phyla in the cold lake. In-depth metagenomic investigation of the cold aquatic habitat revealed novel genes encoding detergent enzymes, amylase, protease, and lipase. Further, metagenome-assembled genomes (MAGs) belonging to the psychrophilic bacterium, Arthrobacter alpinus, were constructed from the metagenomic data. The annotation depicted the presence of detergent enzymes and genes for low-temperature adaptation in Arthrobacter alpinus. Psychrophilic microbial isolates were screened for lipase, protease, and amylase activities to further strengthen the metagenomic findings. A novel strain of Acinetobacter sp. was identified with the dual enzymatic activity of protease and amylase. The bacterial isolates exhibited hydrolyzing activity at low temperatures. This metagenomic study divulged novel genomic resources for detergent industry enzymes, and the bacterial isolates secreting cold-active amylase, lipase, and protease enzymes. The findings manifest that Tsomgo lake is a potential bioresource of cold-active enzymes, vital for various industrial applications. [ABSTRACT FROM AUTHOR]

Long-term monitoring of microbial communities in the rhizosphere of post-fire forests is currently one of the key knowledge gaps. Knowing the time scale of the effects is indispensable to aiding post-fire recovery in vulnerable woodlands, including holm oak forests, that are subjected to a Mediterranean climate, as is the case with forests that are found in protected areas such as the Sierra Nevada National and Natural Park in southeastern Spain. We took rhizosphere soil samples from burned and unburned holm oak trees approximately 3, 6, and 9 years after the 2005 fire that devastated almost 3500 ha in southeastern Spain. We observed that the prokaryotic communities are recovering but have not yet reached the conditions observed in the unburned forest. A common denominator between this fire and other fires is the long-term persistence of three ecosystem recovery biomarkers—specifically, higher proportions of the genera Arthrobacter, Blastococcus, and Massilia in soil microbial communities after a forest fire. These pyrophilous microbes possess remarkable resilience against adverse conditions, exhibiting traits such as xerotolerance, nitrogen mineralization, degradation of aromatic compounds, and copiotrophy in favorable conditions. Furthermore, these biomarkers thrive in alkaline environments, which persist over the long term following forest fires. The relative abundance of these biomarkers showed a decreasing trend over time, but they were still far from the values of the control condition. In conclusion, a decade does not seem to be enough for the complete recovery of the prokaryotic communities in this Mediterranean ecosystem.

In the Xishan coalfield of northern China, the stratified stacking of soil and gangue was applied to limit the acid pollution from high-sulfur coal gangue. In this study, we found that stratified stacking can effectively neutralize the acidity, with the pH value of gangue-leaching water being 6.02–8.13. In contrast to the acidic contaminated area, most of the microorganisms in the study area sediment were neutrophilic, with the main genera being Arthrobacter, Pseudorhodobacter, Pseudomonas, and Rhodoferax. A variety of iron- and sulfur-metabolizing bacteria was discovered in the gangue-leaching sediment, with the total relative abundance ranging from 4.20 to 23.75%, of which the iron-reducing bacteria (FeRB) accounted for the highest percentage. The distributions of these functional microorganisms in the samples were significantly influenced by Fe and S. The co-occurrence network analysis revealed a significant positive correlation between the iron- and sulfur-metabolizing bacteria in the sediment (93.75%), indicating a strong reciprocal symbiotic relationship between these bacteria. The iron and sulfur metabolism genes in the sediment were predicted and compared based on the Tax4Fun functional prediction method. Results showed that functional genes related to iron metabolism were highly expressed in the gangue-leaching sediment. This study enhances the understanding of iron and sulfur metabolism in gangue-leaching contaminated areas. [ABSTRACT FROM AUTHOR]

Pak choi is a vegetable of high nutritional value and palatability, which has promoted the increase of its cultivation and consumption outside Asia, its region of origin. This work evaluated the effect of the inoculation of three strains of plant growth-promoting rhizobacteria (PGPR) Arthrobacter pokkalii JLB4, Pseudomonas tolaasii P61 and Pseudomonas tolaasii A46 on pak choi plants under controlled conditions in a high tunnel in 2021. Pak choi seedlings without inoculation were used as a control and two inoculations were performed, the first immediately after transplantation of the seedlings into bags with 5 kg of soil and the second one month later. The plants were simultaneously fertilized with inoculation with NPK in a ratio 164-53-187. The results obtained showed that the strain Pseudomonas tolaasii P61 was the one that had the greatest effect on dry weight (23.04 ±0.057 g plant-1 ), as well as on the content of P (0.1704 ±0.001 g plant-1 ) and S (0.1847 ±0.004 g plant-1 ) compared to the control, with increases of 11.5%, 10.8% and 12.3%, respectively. The strain Arthrobacter pokkalii JLB4 caused greater root growth, the root volume (75 ±5 ml) was 49% higher than the control. However, it had no effect on the dry weight of the aerial part. The results suggest that the combined use of fertilizer and PGPR leads to greater accumulation of biomass and nutrients, such as P, K and S, than the application of fertilizer alone. [ABSTRACT FROM AUTHOR]

Antarctica is an untapped reservoir of bacterial communities, which are able to adapt to a huge variety of strategies to cope with extreme conditions and, therefore, are capable of producing potentially valuable compounds for biotechnological applications. In this study, 31 UV-resistant bacteria collected from different Antarctic aquatic environments (surface sea waters/ice and shallow lake sediments) were isolated by UV-C assay and subsequently identified. A phylogenetic analysis based on 16S rRNA gene sequence similarities showed that the isolates were affiliated with Proteobacteria, Actinobacteria and Firmicutes phyla, and they were clustered into 15 bacterial genera, 5 of which were Gram negative (Brevundimonas, Qipengyuania, Sphingorhabdus, Sphingobium, and Psychrobacter) and 10 of which were Gram positive (Staphylococcus, Bacillus, Mesobacillus, Kocuria, Gordonia, Rhodococcus, Micrococcus, Arthrobacter, Agrococcus, and Salinibacterium). Strains belonging to Proteobacteria and Actinobacteria phyla were the most abundant species in all environments. The genus Psychrobacter was dominant in all collection sites, whereas bacteria belonging to Actinobacteria appeared to be the most diverse and rich in terms of species among the investigated sites. Many of these isolates (20 of 31 isolates) were pigmented. Bacterial pigments, which are generally carotenoid-type compounds, are often involved in the protection of cells against the negative effects of UV radiation. For this reason, these pigments may help bacteria to successfully tolerate Antarctic extreme conditions of low temperature and harmful levels of UV radiation. [ABSTRACT FROM AUTHOR]

Over the last 30 years, the description of microbial diversity has been mainly based on culture-independent approaches (metabarcoding and metagenomics) allowing an in-depth analysis of microbial diversity that no other approach allows. Bearing in mind that culture-dependent approaches cannot replace culture-independent approaches, we have improved an original method for isolating strains consisting of “culturing” grains of sand directly on Petri dishes (grain-by-grain method). This method allowed to cultivate up to 10% of the bacteria counted on the surface of grains of the three sites studied in the Great Western Erg in Algeria (Timoudi, Béni Abbès, and Taghit), knowing that on average about 10 bacterial cells colonize each grain. The diversity of culturable bacteria (collection of 290 strains) predicted by 16S rRNA gene sequencing revealed that Arthrobacter subterraneus, Arthrobacter tecti, Pseudarthrobacter phenanthrenivorans, Pseudarthrobacter psychrotolerans, and Massilia agri are the dominant species. The comparison of the culture-dependent and - independent (16S rRNA gene metabarcoding) approaches at the Timoudi site revealed 18 bacterial genera common to both approaches with a relative overestimation of the genera Arthrobacter/Pseudarthrobacter and Kocuria, and a relative underestimation of the genera Blastococcus and Domibacillus by the bacterial culturing approach. The bacterial isolates will allow further study on the mechanisms of tolerance to desiccation, especially in Pseudomonadota (Proteobacteria). [ABSTRACT FROM AUTHOR]

The cultivation and consumption of sweet potato (Ipomoea batatas) are increasing globally. As the usage of chemical fertilizers and pest control agents during its cultivation may lead to soil, water and air pollution, there is an emerging need for environment-friendly, biological solutions enabling increased amounts of healthy crop and efficient disease management. Microbiological agents for agricultural purposes gained increasing importance in the past few decades. Our goal was to develop an agricultural soil inoculant from multiple microorganisms and test its application potential in sweet potato cultivation. Two Trichoderma strains were selected: Trichoderma ghanense strain SZMC 25217 based on its extracellular enzyme activities for the biodegradation of plant residues, and Trichoderma afroharzianum strain SZMC 25231 for biocontrol purposes against fungal plant pathogens. The Bacillus velezensis strain SZMC 24986 proved to be the best growth inhibitor of most of the nine tested strains of fungal species known as plant pathogens, therefore it was also selected for biocontrol purposes against fungal plant pathogens. Arthrobacter globiformis strain SZMC 25081, showing the fastest growth on nitrogen-free medium, was selected as a component with possible nitrogen-fixing potential. A Pseudomonas resinovorans strain, SZMC 25872, was selected for its ability to produce indole-3-acetic acid, which is among the important traits of potential plant growth-promoting rhizobacteria (PGPR). A series of experiments were performed to test the selected strains for their tolerance to abiotic stress factors such as pH, temperature, water activity and fungicides, influencing the survivability in agricultural environments. The selected strains were used to treat sweet potato in two separate field experiments. Yield increase was observed for the plants treated with the selected microbial consortium (synthetic community) in comparison with the control group in both cases. Our results suggest that the developed microbial inoculant has the potential to be used in sweet potato plantations. To the best of our knowledge, this is the first report about the successful application of a fungal-bacterial consortium in sweet potato cultivation. [ABSTRACT FROM AUTHOR]

Milk is naturally a rich source of many essential nutrients; therefore, it is quite a suitable medium for bacterial growth and serves as a reservoir for bacterial contamination. The genus Arthrobacter is a food-related bacterial group commonly present as a contaminant in milk and dairy products as primary and secondary microflora. Arthrobacter bacteria frequently demonstrate the nutritional versatility to degrade different compounds even in extreme environments. As a result of their metabolic diversity, Arthrobacter species have long been of interest to scientists for application in various industry and biotechnology sectors. In the dairy industry, strains from the Arthrobacter genus are part of the microflora of raw milk known as an indicator of hygiene quality. Although they cause spoilage, they are also regarded as important strains responsible for producing fermented milk products, especially cheeses. Several Arthrobacter spp. have reported their significance in the development of cheese color and flavor. Furthermore, based on the data obtained from previous studies about its thermostability, and thermoacidophilic and thermoresistant properties, the genus Arthrobacter promisingly provides advantages for use as a potential producer of β-galactosidases to fulfill commercial requirements as its enzymes allow dairy products to be treated under mild conditions. In light of these beneficial aspects derived from Arthrobacter spp. including pigmentation, flavor formation, and enzyme production, this bacterial genus is potentially important for the dairy industry. [ABSTRACT FROM AUTHOR]

Atrazine toxicity is one of the limiting factors inhibiting sensitive plant growth. Previous studies showed that atrazine-degrading bacteria could alleviate atrazine toxicity. However, there is limited information on how atrazine-degrading bacteria and plant growth-promote bacteria alleviate atrazine toxicity in soybeans. Therefore, the current study aimed to explore the atrazine removal, phosphorus utilization, and the oxidative stress alleviation of atrazine-degrading bacterium Arthrobacter sp. DNS10 and/or inorganic phosphorus-solubilizing bacterium Enterobacter sp. P1 in the reduction of atrazine toxicity in soybean. The results showed that atrazine exposure to soybean seedlings led to significant inhibition in growth, atrazine removal, and phosphorus utilization. However, the co-inoculatied strains significantly increased seedlings biomass, chlorophyll a/b contents, and total phosphorus in leaves accompanied by great reduction of the atrazine-induced antioxidant enzymes activities and malonaldehyde (MDA) contents, as well as atrazine contents in soil and soybeans under atrazine stress. Furthermore, transcriptome analysis highlighted that co-inoculated strains increased the expression levels of genes related to photosynthetic-antenna proteins, carbohydrate metabolism, and fatty acid degradation in leaves. All the results suggest that the co-inoculation mitigates atrazine-induced oxidative stress on soybean by accelerating atrazine removal from soil and phosphorus accumulation in leaves, enhancing the chlorophyll contents, and regulating plant transcriptome. It may be suggested that co-inoculation of atrazine-degrading bacteria and inorganic phosphorus-solubilizing bacteria can be used as a potential method to alleviate atrazine toxicity to the sensitive crops. [ABSTRACT FROM AUTHOR]

A new bacterial strain has been isolated from the microbiome of solar panels and classified as Arthrobacter sp. Helios according to its 16S rDNA, positioning it in the “Arthrobacter citreus group.” The isolated strain is highly tolerant to desiccation, UV radiation and to the presence of metals and metalloids, while it is motile and capable of growing in a variety of carbon sources. These characteristics, together with observation that Arthrobacter sp. Helios seems to be permanently prepared to handle the desiccation stress, make it very versatile and give it a great potential to use it as a biotechnological chassis. The new strain genome has been sequenced and its analysis revealed that it is extremely well poised to respond to environmental stresses. We have analyzed the transcriptional response of this strain to PEG6000-mediated arid stress to investigate the desiccation resistance mechanism. Most of the induced genes participate in cellular homeostasis such as ion and osmolyte transport and iron scavenging. Moreover, the greatest induction has been found in a gene cluster responsible for biogenic amine catabolism, suggesting their involvement in the desiccation resistance mechanism in this bacterium.

Inulin is an important fructan in nature, which provides energy to organisms by different metabolic pathways. In one of the metabolic pathways, inulin can be converted to difructose anhydride III (DFA-III) by DFA-III-forming inulin fructotransferase (IFTase-III) and DFA-III can be further hydrolyzed to inulobiose by difructose anhydride III hydrolase (DFA-IIIase). Inulobiose is a kind of fructooligosaccharide that can play a role of prebiotics. However, the low activity of DFA-IIIase is the key factor restricting the production and investigation of inulobiose. Therefore, in this work, the enzymatic activity was attempted to be improved by protein engineering. According to the sequence analysis and homologous modeling, several amino acids involved in the active site and the loop region above the active pocket were modified and eight mutants were constructed. The mutants E389A and E91K obtained significantly increased activities, which were 3.63 and 2.57 times that of the wild-type AcDFA-Ⅲase, respectively. The higher activity of E389A and E91K was possibly ascribed to the higher hydrophobicity of Ala389 and tighter catalytic pocket area formed between Lys91 and His158, respectively. The work explored how to enhance the activity of DFA-IIIase, laying a foundation for mass production, further investigation, and application of inulobiose. [Display omitted] • Difructose anhydride III hydrolase was mutated for enhancing the catalytic activity. • The catalytic activities of mutants E389A and E91K were improved significantly. • The mechanism for the improved catalytic activity of the mutants was elucidated. [ABSTRACT FROM AUTHOR]

Leucaena leucocephala growing in the tropics and subtropics serves as potential forage for livestock because its foliage is rich in protein, fiber, and minerals. However, its use for livestock feed has been hindered by toxic nonprotein amino acid mimosine. Therefore, it is necessary to develop a method to reduce or eliminate mimosine from foliage. A previous study found that the fermentation of L. leucocephala foliage reduced the mimosine content and prompted the authors to isolate potent mimosine degrading microorganisms and characterize the mimosinase for the complete elimination of mimosine in the L. leucocephala foliage. The soil screening of the L. leucocephala tree surroundings led to the isolation of Arthrobacter sp. Ryudai-S1, which can degrade and assimilate mimosine as a nitrogen and carbon source. Mimosinase in this strain was found to be thermostable and showed strong activity. Docking model's inspection and the interaction energy calculation between mimosine-pyridoxal-5ʹ-phosphate (PLP) complex and the active site of this enzyme identified 11 important amino acid residues that stabilized the binding. Of these amino acid residues, mutation experiment suggested that Tyr-263ʹ and Phe-34 stabilizes the substrate binding and play a critical role in guiding the substrate to proper positions to accomplish high catalytic efficacy and selectivity. These observations suggest that Arthrobacter sp. Ryudai-S1 could be potentially useful for the development of L. leucocephala feed with reduced mimosine content. [ABSTRACT FROM AUTHOR]