Complete genome of Arthrobacter alpinus strain R3.8, bioremediation potential unraveled with genomic analysis

Enriched microbial consortia from natural environments reveal core groups of microbial taxa able to degrade terephthalate and terphthalamide

Millions of tons of polyethylene terephthalate (PET) are produced each year, however only ~30% of PET is currently recycled in the United States. Improvement of PET recycling and upcycling practices is an area of ongoing research. One method for PET upcycling is chemical depolymerization (through hydrolysis or aminolysis) into aromatic monomers and subsequent biodegradation. Hydrolysis depolymerizes PET into terephthalate, while aminolysis yields terephthalamide. Aminolysis, which is catalyzed with strong bases, yields products with high osmolality, which is inhibitory to optimal microbial growth. Additionally, terephthalamide, may be antimicrobial and its biodegradability is presently unknown. In this study, microbial communities were enriched from sediments collected from five unique environments to degrade either terephthalate or terephthalamide by performing biweekly transfers to fresh media and substrate. 16S rRNA sequencing was used to identify the dominant taxa in the enrichment cultures which may have terephthalate or terephthalamide-degrading metabolisms and compare them to the control enrichments. The goals of this study are to evaluate (1) how widespread terephthalate and terephthalamide degrading metabolisms are in natural environments, and (2) determine whether terephthalamide is biodegradable and identify microorganisms able to degrade it. The results presented here show that known contaminant-degrading genera were present in all the enriched microbial communities. Additionally, results show that terephthalamide (previously thought to be antimicrobial) was biodegraded by these enriched communities, suggesting that aminolysis may be a viable method for paired chemical and biological upcycling of PET.

Proposal of Crystallibacter gen. nov., Crystallibacter permensis sp. nov. and Crystallibacter degradans sp. nov. for the salt-tolerant and aromatics degrading actinobacteria, and reclassification of Arthrobacter crystallopoietes as Crystallibacter crystallifaciens comb. nov

Four salt-tolerant and aromatics degrading strains used in this study were isolated from polluted technogenic soil on the territory of the Verkhnekamsk potash deposit (Russia). The strains were aerobic, Gram-stain-positive, non-motile, non-endospore-forming irregular rods, exhibiting a marked rod-coccus growth cycle. They contained lysine-based peptidoglycan, teichulosonic acid and poly(glycosyl phosphate) polymers in the cell walls. The major menaquinone was MK-9(H2), the predominant fatty acids were saturated, anteiso- and iso-branched, and the major compounds of polar lipid profiles included phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and two glycolipids (monogalactosyldiacylglycerol and dimannosylglyceride). The strains showed the highest 16S rRNA gene sequence similarity to Arthrobacter crystallopoietes (99.6-99.9%), followed by A. mangrovi (98.3-98.5%) and A. globiformis, the type species of the genus Arthrobacter (97.6-97.8%). The values of overall genome related indices (ANI, dDDH, AAI and POCP) indicated that the target strains and A. crystallopoietes represented three species within a new genus. These species clearly differed from each other and from A. mangrovi and A. globiformis in the phenotypic traits, including the peptidoglycan type and the structures and compositions of cell wall glycopolymers. Based on the findings of this study and the previously published data, we provide the description of the new genus Crystallibacter gen. nov. with the type species Crystallibacter crystallifaciens comb. nov. (type strain, VKM Ac-1107 T) and two newly revealed species, Crystallibacter permensis sp. nov. (type strain, B905T = VKM Ac-2550T = LMG 33113T) and Crystallibacter degradans sp. nov. (type strain, SF27T = VKM Ac-2063T = LMG 33112T).

Freezing and thawing in Antarctica: characterization of antifreeze protein (AFP) producing microorganisms isolated from King George Island, Antarctica

Antarctic temperature variations and long periods of freezing shaped the evolution of microorganisms with unique survival mechanisms. These resilient organisms exhibit several adaptations for life in extreme cold. In such ecosystems, microorganisms endure the absence of liquid water and exhibit resistance to freezing by producing water-binding molecules such as antifreeze proteins (AFP). AFPs modify the ice structure, lower the freezing point, and inhibit recrystallization. The objective of this study was to select and identify microorganisms isolated from different Antarctic ecosystems based on their resistance to temperatures below 0 °C. Furthermore, the study sought to characterize these microorganisms regarding their potential antifreeze adaptive mechanisms. Samples of soil, moss, permafrost, and marine sediment were collected on King George Island, located in the South Shetland archipelago, Antarctica. Bacteria and yeasts were isolated and subjected to freezing-resistance and ice recrystallization inhibition (IR) tests. A total of 215 microorganisms were isolated, out of which 118 were molecularly identified through molecular analysis using the 16S rRNA and ITS regions. Furthermore, our study identified 24 freezing-resistant isolates, including two yeasts and 22 bacteria. A total of 131 protein extracts were subjected to the IR test, revealing 14 isolates positive for AFP production. Finally, four isolates showed both freeze-resistance and IR activity (Arthrobacter sp. BGS04, Pseudomonas sp. BGS05, Cryobacterium sp. P64, and Acinetobacter sp. M1_25C). This study emphasizes the diversity of Antarctic microorganisms with the ability to tolerate freezing conditions. These microorganisms warrant further investigation to conduct a comprehensive analysis of their antifreeze capabilities, with the goal of exploring their potential for future biotechnological applications.

'A plant's major strength in rhizosphere': the plant growth promoting rhizobacteria

Human activities, industrialization and civilization have deteriorated the environment which eventually has led to alarming effects on plants and animals by heightened amounts of chemical pollutants and heavy metals in the environment, which create abiotic stress. Environmental conditions like drought, salinity, diminished macro-and micro-nutrients also contribute in abiotic stress, resulting in decrement of survival and growth of plants. Presence of pathogenic and competitive microorganisms, as well as pests lead to biotic stress and a plant alone can not defend itself. Thankfully, nature has rendered plant's rhizosphere with plant growth promoting rhizobacteria which maintain an allelopathic relationship with host plant to defend the plant and let it flourish in abiotic as well as biotic stress situations. This review discusses the mechanisms behind increase in plant growth via various direct and indirect traits expressed by associated microorganisms in the rhizosphere, along with their current scenario and promising future for sustainable agriculture. It also gives details of ten such bacterial species, viz. Acetobacter, Agrobacterium, Alcaligenes, Arthrobacter, Azospirillum, Azotobacter, Bacillus, Burkholderia, Enterobacter and Frankia, whose association with the host plants is famed for enhancing plant's growth and survival.

Metagenomic views on taxonomic and functional profiles of the Himalayan Tsomgo cold lake and unveiling its deterzome potential

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.

Metabolic Pathway of Phenol Degradation of a Cold-Adapted Antarctic Bacteria, Arthrobacter sp

Phenol is an important pollutant widely discharged as a component of hydrocarbon fuels, but its degradation in cold regions is challenging due to the harsh environmental conditions. To date, there is little information available concerning the capability for phenol biodegradation by indigenous Antarctic bacteria. In this study, enzyme activities and genes encoding phenol degradative enzymes identified using whole genome sequencing (WGS) were investigated to determine the pathway(s) of phenol degradation of Arthrobacter sp. strains AQ5-05 and AQ5-06, originally isolated from Antarctica. Complete phenol degradative genes involved only in the ortho-cleavage were detected in both strains. This was validated using assays of the enzymes catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, which indicated the activity of only catechol 1,2-dioxygenase in both strains, in agreement with the results from the WGS. Both strains were psychrotolerant with the optimum temperature for phenol degradation, being between 10 and 15 °C. This study suggests the potential use of cold-adapted bacteria in the bioremediation of phenol pollution in cold environments.

Genotype to ecotype in niche environments: adaptation of Arthrobacter to carbon availability and environmental conditions

Niche environmental conditions influence both the structure and function of microbial communities and the cellular function of individual strains. The terrestrial subsurface is a dynamic and diverse environment that exhibits specific biogeochemical conditions associated with depth, resulting in distinct environmental niches. Here, we present the characterization of seven distinct strains belonging to the genus Arthrobacter isolated from varying depths of a single sediment core and associated groundwater from an adjacent well. We characterized genotype and phenotype of each isolate to connect specific cellular functions and metabolisms to ecotype. Arthrobacter isolates from each ecotype demonstrated functional and genomic capacities specific to their biogeochemical conditions of origin, including laboratory-demonstrated characterization of salinity tolerance and optimal pH, and genes for utilization of carbohydrates and other carbon substrates. Analysis of the Arthrobacter pangenome revealed that it is notably open with a volatile accessory genome compared to previous pangenome studies on other genera, suggesting a high potential for adaptability to environmental niches.

Comparative genomics and physiological investigation supported safety, cold adaptation, efficient hydrolytic and plant growth-promoting potential of psychrotrophic Glutamicibacter arilaitensis LJH19, isolated from night-soil compost

BACKGROUND

Night-soil compost (NSC) has traditionally been conserving water and a source of organic manure in northwestern Himalaya. Lately, this traditional method is declining due to modernization, its unhygienic conditions, and social apprehensions. Reduction in the age-old traditional practice has led to excessive chemical fertilizers and water shortage in the eco-sensitive region. In the current study, a bacterium has been analyzed for its safety, cold-adaptation, efficient degradation, and plant growth-promoting (PGP) attributes for its possible application as a safe bioinoculant in psychrotrophic bacterial consortia for improved night-soil composting.

RESULTS

Glutamicibacter arilaitensis LJH19, a psychrotrophic bacterium, was isolated from the NSC of Lahaul valley in northwestern Himalaya. The strain exhibited amylase (186.76 ± 19.28 U/mg), cellulase (21.85 ± 0.7 U/mg), and xylanase (11.31 ± 0.51 U/mg) activities at 10 °C. Possessing efficient hydrolytic activities at low-temperature garners the capability of efficient composting to LJH19. Additionally, the strain possessed multiple PGP traits such as indole acetic acid production (166.11 ± 5.7 μg/ml), siderophore production (85.72 ± 1.06% psu), and phosphate solubilization (44.76 ± 1.5 μg/ml). Enhanced germination index and germination rate of pea seeds under the LJH19 inoculation further supported the bacterium's PGP potential. Whole-genome sequencing (3,602,821 bps) and genome mining endorsed the cold adaptation, degradation of polysaccharides, and PGP traits of LJH19. Biosynthetic gene clusters for type III polyketide synthase (PKS), terpene, and siderophore supplemented the endorsement of LJH19 as a potential PGP bacterium. Comparative genomics within the genus revealed 217 unique genes specific to hydrolytic and PGP activity.

CONCLUSION

The physiological and genomic evidence promotes LJH19 as a potentially safe bio-inoculant to formulate psychrotrophic bacterial consortia for accelerated degradation and improved night-soil compost.

Genome Sequence of Arthrobacter sp. UKPF54-2, a Plant Growth-Promoting Rhizobacterial Strain Isolated from Paddy Soil

Arthrobacter sp. strain UKPF54-2, a plant growth-promoting rhizobacterium having the potential ability to control fungal and bacterial pathogens, was isolated from paddy soil in Kumamoto, Japan. We report here the whole-genome sequence of this strain.

Arthrobacter sp. strain UKPF54-2, a plant growth-promoting rhizobacterium having the potential ability to control fungal and bacterial pathogens, was isolated from paddy soil in Kumamoto, Japan. We report here the whole-genome sequence of this strain.

Biodegradation of persistent environmental pollutants by Arthrobacter sp

Persistent environmental pollutants are a growing problem around the world. The effective control of the pollutants is of great significance for human health. Some microbes, especially Arthrobacter, can degrade pollutants into nontoxic substances in various ways. Here, we review the biological properties of Arthrobacter adapting to a variety of environmental stresses, including starvation, hypertonic and hypotonic condition, oxidative stress, heavy metal stress, and low-temperature stress. Furthermore, we categorized the Arthrobacter species that can degrade triazines, organophosphorus, alkaloids, benzene, and its derivatives. Metabolic pathways behind the various biodegradation processes are further discussed. This review will be a helpful reference for comprehensive utilization of Arthrobacter species to tackle environmental pollutants.

Complete Genome Sequence of Arthrobacter sp. Strain MN05-02, a UV-Resistant Bacterium from a Manganese Deposit in the Sonoran Desert

Arthrobacter sp. strain MN05-02 is a UV-resistant bacterium isolated from a manganese deposit in the Sonoran Desert, Arizona, USA. The LD₁₀ of this strain is 123 Jm^-2, which is twice that of Escherichia coli, and therefore can be a useful resource for comparative study of UV resistance and the role of manganese on this phenotype. Its complete genome is comprised of a chromosome of 3,488,433 bp and a plasmid of 154,991 bp. The chromosome contains 3,430 putative genes, including 3,366 protein coding genes, 52 tRNA and 12 rRNA genes. Carotenoid biosynthesis operon structure coded within the genome mirrors the characteristic orange-red pigment this bacterium produces, which presumably partly contribute to its UV resistance.