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Soil is one of the great reservoirs of microorganisms. A multiple-metal resistant Pseudomonas aeruginosa strain isolated from arable soil was screened for lipase activity since it plays a crucial role in bacterial cellular metabolism. This strain showed higher minimum inhibitory concentrations for the metal Ni, Zn and Cd. The effect of these heavy metals on lipase production was studied by examining qualitative and quantitative aspects of lipase activity in tributyrin agar base medium and lipase production media, respectively. The lipase activity was found to be 304.45 U/L in the control group (without heavy metals), which was higher than in the groups treated with heavy metals. A statistically significant difference was detected in the metal-induced alteration of the lipolytic activity of the studied strain. The inhibitory effect of the heavy metals on lipase production was assessed, with Zn showing the highest inhibition, while Ni exhibited the lowest inhibitory effect among the three metals studied. The lipolytic activity of the strain was altered by the heavy metals, as demonstrated by ATR-FTIR analysis that revealed changes in the functional groups involved in lipase production under heavy metal stress compared to the control. This study is the first attempt to investigate the extracellular lipase activity of a multiple heavy metal-resistant Pseudomonas strain isolated from arable soil of Uttar Dinajpur region of West Bengal, India, which requires further research for future utilization. [ABSTRACT FROM AUTHOR]

Cellulose degrading bacterial diversity of Bhitarkanika mangrove ecosystem, India, was uncovered and the cellulose degradation mechanism in Bacillus haynesii DS7010 under the modifiers such as pH (pCO 2), salinity and lead (Pb) was elucidated in the present study. The abundance of cellulose degrading heterotrophic bacteria was found to be higher in mangrove sediment than in water. The most potential strain, B. haynesii DS7010 showed the presence of endoglucanase, exoglucanase and β-glucosidase with the maximum degradation recorded at 48 h of incubation, with 1% substrate concentration at 41 °C incubation temperature. Two glycoside hydrolase genes, celA and celB were confirmed in this bacterium. 3D structure prediction of the translated CelA and CelB proteins showed maximum similarities with glycoside hydrolase 48 (GH48) and glycoside hydrolase 5 (GH5) respectively. Native PAGE followed by zymogram assay unveiled the presence of eight isoforms of cellulase ranged from 78 kDa to 245 kDa. Among the stressors, most adverse effect was observed under Pb stress at 1400 ppm concentration, followed by pH at pH 4. This was indicated by prolonged lag phase growth, higher reactive oxygen species (ROS) production, lower enzyme activity and downregulation of celA and celB gene expressions. Salinity augmented bacterial metabolism up to 3% NaCl concentration. Mangrove leaf litter degradation by B. haynesii DS7010 indicated a substantial reduction in cellulolytic potential of the bacterium in response to the synergistic effect of the stressors. Microcosm set up with the stressors exhibited 0.97% decrease in total carbon (C%) and 0.02% increase in total nitrogen (N%) after 35 d of degradation while under natural conditions, the reduction in C and the increase in N were 4.05% and 0.2%, respectively. The findings of the study suggest the cellulose degradation mechanism of a mangrove bacterium and its resilience to the future consequences of environmental pollution and climate change. [Display omitted] • GH48 and GH5 were confirmed within the cellulolytic system of B. haynesii DS7010. • Native PAGE with zymogram assay revealed the presence of eight cellulase isoforms. • Variable pH/pCO 2 and lead (Pb) negatively affected bacterial metabolism. • Salinity stress exhibited a positive effect on the bacterium up to 3% concentration. • Bacterial leaf litter degradation was severely affected by cumulative effect of stressors. [ABSTRACT FROM AUTHOR]

Silver carp is an invasive fish present in the Gobindsagar reservoir, India and has a profound impact on aquaculture. Understanding taxonomic diversity and functional attributes of gut microbiota will provide insights into the important role of bacteria in metabolism of silver carp that facilitated invasion of this exotic species. Microbial composition in foregut, midgut, hindgut and water samples was analysed using 16S rRNA gene amplicon sequencing. The bacterial communities of water samples were distinct from gut microbiota, and unique microbial assemblages were present in different regions of gut depicting profound impact of gut environment on microflora. Proteobacteria was the most abundant phyla across all samples. Ecological network analysis showed dominance of competitive interactions within posteriors region of the gut, promoting niche specialization. Predictive functional profiling revealed the microbiota specialized in digestive functions in different regions of the gut, which also reflects the dietary profile of silver carp. • Gut microbiome analysis of exotic silver carp using amplicon sequencing. • Gut environment drives the microbial community composition of silver carp. • Interspecies interactions indicate niche specialization of microbes in the gut. • Functional profiling depicts the role of gut microflora in digestion of the host. [ABSTRACT FROM AUTHOR]

" Candidatus Nitrosocaldaceae" are globally distributed in neutral or slightly alkaline hot springs and geothermally heated soils. Despite their essential role in the nitrogen cycle in high-temperature ecosystems, they remain poorly understood because they have never been isolated in pure culture, and very few genomes are available. In the present study, a metagenomics approach was employed to obtain " Ca. Nitrosocaldaceae" metagenomic-assembled genomes (MAGs) from hot spring samples collected from India and China. Phylogenomic analysis placed these MAGs within " Ca. Nitrosocaldaceae." Average nucleotide identity and average amino acid identity analysis suggested the new MAGs represent two novel species of " Candidatus Nitrosocaldus" and a novel genus, herein proposed as " Candidatus Nitrosothermus." Key genes responsible for chemolithotrophic ammonia oxidation and a thaumarchaeal 3HP/4HB cycle were detected in all MAGs. Furthermore, genes coding for urea degradation were only present in " Ca. Nitrosocaldus," while biosynthesis of the vitamins, biotin, cobalamin, and riboflavin were detected in almost all MAGs. Comparison of " Ca. Nitrosocaldales/Nitrosocaldaceae" with other AOA revealed 526 specific orthogroups. This included genes related to thermal adaptation (cyclic 2,3-diphosphoglycerate, and S-adenosylmethionine decarboxylase), indicating their importance for life at high temperature. In addition, these MAGs acquired genes from members from archaea (Crenarchaeota) and bacteria (Firmicutes), mainly involved in metabolism and stress responses, which might play a role to allow this group to adapt to thermal habitats. [ABSTRACT FROM AUTHOR]

The present investigation deals with the characterisation of three As‐resistant bacteria, Bacillus aryabhattai strain VPS1, Bacillus licheniformis strain VPS6 and Sporosarcina thermotolerans strain VPS7 isolated from the rhizosphere of a contaminated paddy field in Chakdaha, Nadia, West Bengal, India. Two strains, VPS6 and VPS7 showed ureolytic activity, which can be used for microbial‐induced calcite precipitation of As as a bioremediation option. However, As reduction and oxidation capacities were not reported in any of these bacteria. A phylogenetic tree of 16S ribosomal RNA gene sequences was constructed for all three bacterial isolates, including different species of As‐resistant Bacillus and Sporosarcina. Furthermore, literature survey and genome mining were employed to explore the diversity of As resistance‐related proteins, arsenite S‐adenosylmethyltransferase (ArsM) and arsenical pump membrane protein (ArsB) among different bacteria, and the phylogenetic relatedness was studied to understand the distribution and evolution of their amino acid sequences. ArsB was predominantly present in a wide variety of bacteria (347 taxa); however, ArsM was reported in comparatively fewer isolates (109 taxa). There were a total of 60 similar taxa that contained both ArsM and ArsB. Both proteins were most abundantly present in phylum Proteobacteria. Overall, this investigation enumerates As‐resistant bacteria to understand the As metabolism in the environment, and the phylogenetic analysis of As resistance‐related proteins helps in understanding the functional relationship in different bacteria for their role in As mobility in the environment. [ABSTRACT FROM AUTHOR]

Hot springs support diverse and interesting groups of microorganisms adapted to extreme conditions and gaining attention in biotechnological applications. However, due to limitations of cultivation methods, a majority of such extremophiles remain uncultivated and unexplored. The advent of multiple cultivation conditions and specialized culture media could possibly aid to access the unexplored microbial portion of hot springs. In the present study, different media and isolation strategies were applied to isolate hitherto unexplored bacterial taxa in the water samples collected from Unkeshwar hot springs, India. Molecular, phylogenetic and predictive functional characterization of the isolated bacterial population was done using 16S rRNA sequencing coupled with Tax4Fun tools. Furthermore, representative isolates were screened for important enzymes (cellulase, xylanase, amylase, and protease) and heavy metal tolerance (chromium, arsenic) properties. A total of 454 bacterial isolates obtained were mapped into 57 unique bacterial genera and 4 different bacterial phyla. Interestingly, 37 genera not previously isolated from Indian hot springs, were isolated for the first time in the present study. However, most of these genera (23 out of 37) were reported only in metagenomics studies from Indian and global hot springs. Furthermore, around 14 genera not previously cultivated and not detected in metagenomics studies of hot springs are documented here. The metabolic potential was ascertained by determining the abundance of specific genes using in silico based Tax4Fun tool, which identified around 315 metabolic pathways for metabolism of carbohydrates, synthesis of secondary metabolites and degradation of xenobiotic compounds. Bioprospection study revealed that 33 and 25 bacterial genera were positive for enzyme production and resistance to the heavy metals, respectively. The present study revealed the advantages of cultivation methods using a comprehensive multiple isolation approach for exploring untapped and unique bacterial diversity, and also utilities for various biotechnological and environmental applications. [ABSTRACT FROM AUTHOR]

Bacteria play a central role in the oxidation of organic matter. In tropical estuaries, bacterial metabolic rates and carbon modification are regulated by physicochemical changes influenced by the annual monsoon-mediated river runoff. The present study is the first report on the effect of monsoon-influenced river discharge magnitude on bacterial metabolic rates and organic matter variation in the tropical Godavari estuary and adjacent coastal waters. Concentrations, nature, and sources of particulate organic carbon and nitrogen were investigated by elemental analyser-isotopic ratio mass spectrometer, whereas concentrations of dissolved organic carbon and nitrogen were determined by a high-temperature catalytic oxidation in surface waters of Godavari estuary, east coast of India. Bacterial abundance and metabolic rates were measured, and pCO2 levels were calculated for surface water samples. The maxima obtained in bacterial respiration (BR) rate (994 μg C l−1 d−1) were associated with maximum concentrations and the terrigenous nature of organic matter with high C:N ratio (∼12). The highly depleted δ13C POC (−32.9 ± 1.4‰) associated with Chl-a maxima suggest its contribution from freshwater planktons. The significant positive correlation of bacterial productivity (BP), bacterial growth efficiency (BGE), and BR with particulate organic matter associated with low DOC:POC ratio could imply a heterotrophic preference for an abundant form of organic matter. We, moreover, uncovered that terrigenous organic matter is modified efficiently in the estuarine transect by heterotrophic bacteria under favorable physicochemical conditions like low salinity and high nutrient content. Furthermore, the majority (76%) of BGE values were <8%, and average pCO2 levels were ∼14 times greater than the atmospheric levels. Overall, this study reported that the Godavari estuary is net heterotrophic and hence significantly contributes to global carbon cycle biogeochemistry. [ABSTRACT FROM AUTHOR]

Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics. [ABSTRACT FROM AUTHOR]

Twenty five different arsenite (AsIII) oxidising bacteria were isolated from industrial effluent (Bilimora, Gujarat Industrial Development Corporation (GIDC) Gujarat, India). The most efficient arsenite oxidiser and arsenite hyper-tolerant bacterial isolate which could tolerate up to 15 mM AsIIIwas selected and 16S rRNA gene sequence analysis was performed. It showed 98% identity of the 16S rRNA genes of genusAlishewanella(Accession no.: HQ659190). Higher activities of arsenite oxidase enzymes in the bacterium were localised on membrane. The GIDC-5 bacterial strain was found to be susceptible to most of the common antibiotics. The optimum growth in the presence of metalloid was observed at temperature 37°C and pH 4, whereas in the absence of metalloid the optimum pH was 8. The result suggested that,Alishewanellasp. strain GIDC-5 demonstrated hyper-tolerant to arsenite because of its ability to overcome the toxic effects of arsenite by converting it to less toxic forms (arsenate). [ABSTRACT FROM AUTHOR]

Aims: To study the microbial communities in three sites contaminated with chlorinated pesticides and evaluation of dehydrodechlorinase ( linA) gene variants involved in gamma-hexachlorocyclohexane (γ-HCH, lindane) degradation. Methods and Results: Using a culture-independent method, 16S rRNA genes were amplified from microbial communities occurring in contaminated soils. From 375 clone libraries analysed, 55 different restriction fragment length polymorphism phylotypes were obtained. Dehydrodechlorinase ( linA) gene, which initiates the γ-HCH degradation, was directly amplified by PCR from the DNA extracted from soils. Deduced amino acid sequences of eight variant genotypes of linA showed few amino acid changes. All the variants of linA had mutations of F151L and S154T, and one of the genotype carried 12 amino acid changes when compared to a linA of Sphingomonas sp. reported from the same soil. Conclusions: The microbial communities displayed complex and diverse groups similar to bacteria involved in biodegradation. The presence of biodegradative genes like linA indicates the presence of communities with capacity to biodegrade the persistent pesticide HCH. Significance and Impact of the Study: This study provides insights to evaluate the presence of catabolic genes and assessing the bioremediation potential of the industrial soils contaminated by chlorinated pesticides. [ABSTRACT FROM AUTHOR]

A bacterial strain Rhodococcus imtechensis RKJ300 (= MTCC 7085T = JCM 13270T) was isolated from pesticide-contaminated soil of Punjab by the enrichment technique on minimal medium containing 4-nitrophenol. Strain RKJ300 is capable of utilizing 4-nitrophenol, 2-chloro-4-nitrophenol, and 2,4-dinitrophenol as sole sources of carbon and energy. The strain involved both oxidative and reductive catabolic mechanisms for initial transformation of these compounds. In the case of 2-chloro-4-nitrophenol, colorimetric analysis indicated that nitrite release was followed by stoichiometric elimination of chloride ions. Experiments using whole cells and cell-free extracts showed chlorohydroquinone and hydroquinone as the intermediates of 2-chloro-4-nitrophenol degradation. This is the first report of degradation on 2-chloro-4-nitrophenol by a bacterium under aerobic condition to the best of our knowledge. However, pathways for degradation of 4-nitrophenol and 2,4-dinitrophenol were similar to those reported in other strains of Rhodococcus. Laboratory-scale soil microcosm studies demonstrated that the organism was capable of degrading a mixture of nitrophenols simultaneously, indicating its applicability toward in situ bioremediation of contaminated sites. The fate of the augmented strain as monitored by the plate-counting method and hybridization technique was found to be fairly stable throughout the period of microcosm experiments. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effect of long-term irrigation of sewage contaminated with heavy metals like Cd, Cr, Cu and Pb on microbial and biochemical parameters of soils of West Bengal, India. The microbial parameters included microbial biomass carbon (MBC), microbial metabolic quotient; the biochemical parameters included fluorescein diacetate hydrolyzing activity, β-glucosidase, urease, phosphatase, and aryl sulphatase activities. A sequential extraction technique was used to quantify water soluble, exchangeable, carbonate bound, Fe/Mn-oxide bound, organically bound, and residual metal fractions. Metal concentrations in the two most labile fractions (i.e., water soluble and exchangeable fractions) were generally low. Total metal concentrations at each site seemed to be associated with soil amorphous Fe and Al minerals. The MBC and the enzymes studied were significantly and negatively correlated with water soluble and exchangeable metals but not significantly correlated with other forms, indicating that water soluble and exchangeable forms exerted a strong inhibitory effect on the soil microbial and biochemical parameters. It was concluded that irrigating soils with metal contaminated sewage seemed to damage soil quality in the long term. [Copyright &y& Elsevier]

Abstract  The present study was conducted to investigate the effects of different forms of soil acidities on microbial biomass C, ergosterol content, microbial metabolic quotient, microbial respiration quotient, and fluorescein diacetate-hydrolyzing activity of some tea-growing soils of India. Total potential and exchangeable acidity and extractable and exchangeable aluminum were higher in Tripura followed by Jalpaiguri and Kharagpur soil. Different forms of acidity were significantly and positively correlated with each other. All the microbiological properties investigated were significantly and positively correlated with soil organic C content. The ratio of organic C with microbial parameters was significantly and negatively correlated with different forms of acidity. Principal component analysis indicated that the microbial activities were not directly affected by the extractable aluminum and total potential acidity. Although the tea soils had higher microbial biomass and activities because of higher organic matter content than other soils, the ratios of microbial parameters/organic carbon indicated that inhibition of microbial growth and activities had occurred because of acidity stress. [ABSTRACT FROM AUTHOR]

Large areas of mangroves in India are heavily disturbed by cattle grazing, hypersalinity, and other human-induced impacts. In two disturbed Avicennia marina forests and two undisturbed A. marina and Rhizophora apiculata forests in the Pichavaram mangroves of the Vellar–Coleroon estuarine complex, southeast India, we measured the rates and pathways of microbial decomposition of soil organic matter to determine if human impact is altering biogeochemical activity within these stands. Rates of total carbon oxidation ( TCOX) were higher in the undisturbed A. marina forest (mean 199 mol C m−2 year−1) than in the two impacted stands (43 and 79 mol C m−2 year−1); rates of total carbon oxidation in the R. apiculata forest averaged 75 mol C m−2 year−1. Sulphate reduction (range 21–319 mmol S m−2 day−1) was the major decomposition pathway (65–85% of TCOX), except at the most disturbed forest (30% of TCOX). Rates of sulphate reduction at all sites peaked in sub-surface soils to a depth of about 1 m, leading to little carbon burial (3–5% of total C input). There was some evidence of measurable iron and manganese reduction in association with tree roots. Rates of microbial activity were rapid in comparison with rates measured in other mangrove soils, reflecting high rates of phytoplankton production and organic matter retention in this lagoon. Human-induced disturbance creates a sharp zonation of dry, hypersaline soil overlying less saline, wetter soil, suppressing surface microbial and root growth. We conclude that this vertical alteration of soil characteristics and biogeochemistry shifts the cycling of nutrients between trees and microbes to a disequilibrium state, partly explaining why mangroves are stunted in these declining forests. [ABSTRACT FROM AUTHOR]