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Smokeless tobacco (ST) consumption keeps human oral health at high risk which is one of the major reasons for oral tumorigenesis. The chemical constituents of the ST products have been well discussed; however, the inhabitant microbial diversity of the ST products is less explored especially from south Asian regions. Therefore, the present investigation discusses the bacteriome-based analysis of indigenous tobacco products. The study relies on 16S amplicon-based bacteriome analysis of Indian smokeless tobacco (ST) products using a metagenomic approach. A total of 59,15,143 high-quality reads were assigned to 34 phyla, 82 classes, 176 orders, 256 families, 356 genera, and 154 species using the SILVA database. Of the phyla (> 1%), Firmicutes dominate among the Indian smokeless tobacco followed by Proteobacteria, Bacteroidetes, and Actinobacteria (> 1%). Whereas, at the genera level (> 1%), Lysinibacillus, Dickeya, Terribacillus, and Bacillus dominate. The comparative analysis between the loose tobacco (LT) and commercial tobacco (CT) groups showed no significant difference at the phyla level, however, only three genera (Bacillus, Aerococcus, and Halomonas) were identified as significantly different between the groups. It indicates that CT and LT tobacco share similar bacterial diversity and poses equal health risks to human oral health. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt 2.0) based analysis uncovered several genes involved in nitrate/nitrite reduction, biofilm formation, and pro-inflammation that find roles in oral pathogenesis including oral cancer. The strong correlation analysis of these genes with several pathogenic bacteria suggests that tobacco products pose a high bacterial-derived risk to human health. The study paves the way to understand the bacterial diversity of Indian smokeless tobacco products and their putative functions with respect to human oral health. The study grabs attention to the bacterial diversity of the smokeless tobacco products from a country where tobacco consumers are rampantly prevalent however oral health is of least concern. [ABSTRACT FROM AUTHOR]

Smokeless tobacco product (STP) consumption is a significant public health threat across the globe. STPs are not only a storehouse of carcinogens and toxicants but also harbor microbes that aid in the conversion of tobacco alkaloids to carcinogenic tobacco-specific nitrosamines (TSNAs), thereby posing a further threat to the health of its consumers. The present study analyzed the bacterial diversity of popular dry and loose STPs by 16S rRNA gene sequencing. This NGS-based investigation revealed four dominant phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria and identified 549 genera, Prevotella, Bacteroides, and Lactobacillus constituting the core bacteriome of these STPs. The most significantly diverse bacteriome profile was displayed by the loose STP Mainpuri kapoori. The study further predicted the functional attributes of the prevalent genera by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) algorithm. Genes encoding for nitrate and nitrite reduction and transport enzymes, antibiotic resistance, multi-drug transporters and efflux pumps, secretion of endo- and exotoxin, and other pro-inflammatory molecules were identified. The loose STPs showed the highest level of nitrogen metabolism genes which can contribute to the synthesis of TSNAs. This study reveals the bacteriome of Indian domestic loose STPs that stagger behind in manufacturing and storage stringencies. Our results raise an alarm that the consumption of STPs harboring pathogenic genera can potentially lead to the onset of several oral and systemic diseases. Nevertheless, an in-depth correlation analysis of the microbial diversity of STPs and their elicit impact on consumer health is warranted. Key points: • Smokeless tobacco harbors bacteria that aid in synthesis of carcinogenic nitrosamines. • Most diverse bacteriome profile was displayed by loose smokeless tobacco products. • Pathogenic genera in these products can harm the oral and systemic health of users. [ABSTRACT FROM AUTHOR]

To characterize the metabolic versatility of denitrifying bacterial communities residing in the paddy soil, phospholipid fatty acid (PLFA) analyses were done along with nosZ encoding nitrous oxide reductase gene-based PCR-DGGE and real-time Q-PCR analysis. In this study, we have analyzed the abundance of nitrous oxide reductase (nosZ) genes and DGGE-based denitrifier community assessment was found to be correlated with soil PLFA profile in terms of their pattern analysis. Among all detected denitrifying bacteria, Ochrobactrum sp. represented a major fraction following Cupriavidus and uncultured bacteria. The data related to nosZ gene abundance were found to show similar pattern with PLFA-based lipid profile. Greater amount of lipid content (C18-C20) and denitrifiers diversity was apparently visible at Chandauli of Eastern UP, India and thus positively impact each other in the soil. Our study suggests that the nosZ-based DGGE and gene abundance data were increased in response to soil PLFA profiles. Subsequently, the presence of an increased lipid content of soil samples with increased abundance and diversity of denitrifying bacteria could be helpful in managing nutrient dynamics as well as microbial dynamics of paddy soil ecosystem. [ABSTRACT FROM AUTHOR]

Seasonal variations in nitrogen (N2 ) fixation and denitrification rates were estimated in the sediment of Sundarban mangrove ecosystem, India. The mean rate of microbial N2 fixation (16.53 ηmol N fixed/hr/g dry wt of sediment) was relatively higher than the mean rate of denitrification (14.72 ηmol N2O-N /hr/dry wt of sediment) in the mangrove sediment throughout the study, suggesting satisfactory fertility of this ecoregion in terms of sediment nitrogen. Sediment from the deeper parts of this ecosystem showed higher N2 fixation rate (18.23 ηmol N fixed/hr/g dry wt of sediment) than the surface sediment (10.17 ηmol N fixed/hr/g dry wt of sediment). Similar trend was observed for the denitrification rate in all the seasons. The ratio of N2 fixation to denitrification rate showed an increasing trend with depth. The results depicted that under higher anoxic condition bacteria would prefer N2 fixation over denitrification and would ultimately enhance the nitrogen storage capacity of this mangrove ecosystem. Although population of free living N2 fixing bacteria decreased with increase in depth, the rate of N2 fixation showed a reverse trend, during the study period. These results suggested that anoxic condition and low level of nitratenitrogen content could stimulate the enzyme activity responsible for N2 fixation in this particular ecosystem. [ABSTRACT FROM AUTHOR]

Nitrate reducing potency of 88 bacterial isolates segregated from marine and brackish water nitrifying bacterial consortia ( NBC), generated for activation of nitrifying bioreactors, was confirmed by determining the nitrate reducing capability under aerobic conditions as maintained in nitrifying bioreactors. All the isolates had the potential to be used as bio-augmentors for activating nitrate dissimilation in recirculating aquaculture system. The existence of nitrate reducers with nitrifiers in NBC and in the reactor configuration negates the requirement of integrating anoxic denitrifying system for effective removal of NO3−-N. Phylogenetic analyses of representative isolates from each cluster of the dendrograms generated based on phenotypic characterization and amplified ribosomal DNA restriction analysis revealed profound diversity of nitrate reducing bacterial flora in the NBC. They were composed of Streptomyces enissocaesilis, Marinobacter sp., Pseudomonas sp ., Microbacterium oxydans, Pelagibacterium halotolerans and Alcanivorax dieselolei from marine NBC and Streptomyces tendae, Nesterenkonia sp., Bacillus cereus, Microbacterium oxydans and Brevibacterium sp. from brackish water NBC. The diversity indices of the consortia were calculated using Mega 5.0, primer 7 and VITCOMIC softwares. Marine NBC exhibited higher Shannon wiener diversity and mean population diversity than brackish water NBC. The study delineated higher species richness and diversity in marine NBC than in its brackish water counterpart, a possible reflection of the higher biodiversity of marine systems, and hence, the former is more promising to be used as start-up cultures for the activation of nitrifying bioreactors after appropriate acclimatization to the desired salinity. [ABSTRACT FROM AUTHOR]

Abstract: Denitrifying bacteria in brackishwater shrimp culture pond sediments were isolated and characterized from a total of eight samples. Out of the 264 isolates obtained, only 108 (40.96%) were positive for nitrate reduction and only 14 (12.96%) were positive for both nitrate and nitrite reduction. These fourteen isolates have been characterized based on complete reduction of nitrate to gas, presence of denitrification genes (nirS, nirK and nosZ), reverse transcriptase PCR for nirS gene and quantification of nitrous oxide after blocking the nitrous oxide reductase with acetylene. Out of the 14 isolates, nine were identified as Marinobacter spp., and the others belonged to Shewanella sp., Aquamicrobium sp., Marinimicrobium sp., Microbulbifer sp. and Janibacter sp. None of the denitrification genes could be detected in two of the isolates (CDN1 and 12) that reduced both nitrate and nitrite. RT-PCR analysis of all the Marinobacter isolates showed that nirS gene expression is better under anoxic than under oxic conditions indicating their ability to adapt to varying dissolved oxygen concentration. Results revealed that all the Marinobacter isolates are capable of denitrification under oxic, oxygen tolerant and anoxic conditions and indicated that nirS gene containing bacteria of the order Alteromonadales are one of the predominant denitrifying bacteria in brackishwater shrimp culture ponds of India. The study highlights the significance of such brackishwater ecosystems as study sites for future investigations on distribution and diversity of denitrifying bacteria and their role in the nitrogen cycle. [Copyright &y& Elsevier]

Abstract: Denitrification, anammox (Anx) and di-nitrogen fixation were examined in two mangrove ecosystems- the anthropogenically influenced Divar and the relatively pristine Tuvem. Stratified sampling at 2 cm increments from 0 to 10 cm depth revealed denitrification as the main process of N2 production in mangrove sediments. At Divar, denitrification was ∼3 times higher than at Tuvem with maximum activity of 224.51 ± 6.63 nmol N2 g−1 h−1 at 0–2 cm. Denitrifying genes (nosZ) numbered up to 2 × 107 copies g−1 sediment and belonged to uncultured microorganisms clustering within Proteobacteria. Anammox was more prominent at deeper depths (8–10 cm) mainly in Divar with highest activity of 101.15 ± 87.73 nmol N2 g−1 h−1 which was 5 times higher than at Tuvem. Di-nitrogen fixation was detected only at Tuvem with a maximum of 12.47 ± 8.36 nmol N2 g−1 h−1. Thus, in these estuarine habitats prone to high nutrient input, N2-fixation is minimal and denitrification rather than Anx serves as an important mechanism for counteracting N loading. [Copyright &y& Elsevier]

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]

Abstract: Denitrification is a microbial process during which nitrate or nitrite is reduced under anaerobic condition to gaseous nitrogen. The Arabian Sea contains one of the major pelagic denitrification zones and in addition to this, denitrification also takes places along the continental shelf. Prokaryotic microorganisms were considered to be the only players in this process. However recent studies have shown that higher microeukaryotes such as fungi can also adapt to anaerobic mode of respiration and reduce nitrate to harmful green house gases such as NO and N2O. In this study we examined the distribution and biomass of fungi in the sediments of the seasonal anoxic region off Goa from two stations. The sampling was carried out in five different periods from October 2005, when dissolved oxygen levels were near zero in bottom waters to March 2006. We isolated mycelial fungi, thraustochytrids and yeasts. Species of Aspergillus and thraustochytrids were dominant. Fungi were isolated under aerobic, as well as anaerobic conditions from different seasons. Four isolates were examined for their denitrification activity. Two cultures obtained from the anoxic sediments showed better growth under anaerobic condition than the other two cultures that were isolated from oxic sediments. Our preliminary results suggest that several species of fungi can grow under oxygen deficient conditions and participate in denitrification processes. [Copyright &y& Elsevier]

Abstract: [I.] Field studies were carried out 1 year to understand the distribution of culturable bacteria in the coastal waters in relation to the thermal discharge. [II.] Laboratory experiments were carried out to determine the effect of the two major stress factors, namely, temperature and chlorine, on bacterial strains isolated from the study site. [III.] Culturable aerobic heterotrophic bacteria (CAHB) populations at thermally impacted stations were less than those at control stations. However, richer were nitrate-reducing bacteria (NRB) population near the plant discharge, as compared with the control site. [IV.] Among the three species of bacteria tested, expression of the heat shock protein HSP 70 was evident in Pseudoalteromonas ruthenica (SBT033), but not in Staphylococcus sp. (SBT 120) and Bacillus sp. (SBT 324). [Copyright &y& Elsevier]

With the progradation of Godavari delta in the east coast of India, increase in iron (Fe) concentrations in the groundwater was observed. High concentrations of Fe (>10 mg/l) were observed in khondalite and charnockite formations. A lower portion of the Godavari river basin, viz. East Godavari district was chosen for the study of the distribution of iron with special reference to the existing geological formations and the geomorphology of the area. The concentration of iron was observed to vary from below detection limit to 69 mg/l in the groundwater while it was less than 1 mg Fe/l in river and spring waters. The Fe of river water was reduced due to seawater mixing and the electrical conductivity (EC) was increased approximately to half of the seawater conductivity. Unlike the mixing of seawater at the surface, the same seawater mixing with groundwater yielded a water having similar order of EC with relatively high Fe. Fe was inversely related with nitrate in the groundwater. Fe was found to correlate considerably better with manganese in fluvial and coastal alluvium zones. The locations having higher Fe in delta are suspected to be related to palaeo channels. The association between Fe and Mn and their negative association with NO3 may be due to the possible autotrophic denitrification that might have taken place in the subsurface. [ABSTRACT FROM AUTHOR]

Crop growth simulation models provide a means to quantify the effects of climate, soil and management on crop growth and biogeochemical processes in soil. The Denitrification and Decomposition (DNDC) model was evaluated for its ability to simulate methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from Indian rice fields with various management practices. The model was calibrated and validated for field experiments in New Delhi, India. The observed yield, N uptake and greenhouse gas (GHG) emissions were in good agreement with the values predicted by the model. The model was then applied for estimation of GHG emissions from rice fields in India using a newly compiled soil/climate/land use database. Continuous flooding of rice fields (42.25 million ha) resulted in annual net emissions of 1.07-1.10, 0.038-0.048 and 21.16-60.96 Tg of CH4-C, N2O-N and CO2-C, respectively, with a cumulated global warming potential (GWP) of 130.93-272.83 Tg CO2 equivalent. Intermittent flooding of rice fields reduced annual net emissions to 0.12-0.13 Tg CH4-C and 16.66-48.80 Tg CO2-C while N2O emission increased to 0.056-0.060 Tg N2O-N. The GWP, however, reduced to 91.73-211.80 Tg CO2 equivalent. The study suggests that the model can be applied for studying the GHG related issues in rice cropping systems of India. [ABSTRACT FROM AUTHOR]