Browsing by Author "P. Vishwakarma"

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Changes in methanotrophic community composition after rice crop harvest in tropical soils
(2010) P. Vishwakarma; M. Singh; S.K. Dubey
Four selected tropical field sites from India were studied to assess the diversity and community structure of methanotrophs in rice fields following crop harvest. The rate of methane oxidation ranged from 0.04 to 0.11 μmol L-1 h-1 g-1 dry weight in soils. Methanotrophic population size was high for the agriculture farm of Banaras Hindu University (BHU) site followed by agriculture farm of the Indian Institute of Vegetable Research (IIVR), Ghazipur, and Barkachcha. The cloning, restriction fragment length polymorphism, and sequence analyses of the pmoA gene fragment amplified from soil DNA extracts revealed the presence of type I and type II methanotrophs. The phylogenetic affiliation and community analysis based on the presence or absence of sequences showed that methanotrophs community composition in Barkachcha and Ghazipur soils was similar. IIVR soils, however, were quite different, while BHU soils were intermediate among the sites with regard to methanotrophic community composition. Diversity index of the methanotrophic community was high at the IIVR site. The study revealed that the rice harvest led to a change in type I methanotrophs from all the sites while type II community composition was almost uniform. © 2010 Springer-Verlag.
Kinetic and molecular analyses reveal isoprene degradation potential of Methylobacterium sp.
(Elsevier Ltd, 2017) Navnita Srivastva; P. Vishwakarma; Y. Bhardwaj; A. Singh; K. Manjunath; Suresh K. Dubey
Efforts were made to isolate and characterize bacteria capable of growing on methane and organic compounds, and to achieve the simultaneous degradation of more than one pollutant. Among the methanotrophs, species of Methylobacterium was able to catabolize a variety of hydrocarbons, including the branched-chain alkenes. Therefore, laboratory incubations experiments were carried out in batch mode to assess the potential of Methylobacterium sp. PV1 for degrading isoprene, the low-molecular-weight alkene, the most abundant non-methane volatile hydrocarbon present in the environment. Methylobacterium sp. PV1, isolated from paddy field soil, was characterized by pmoA and 16S rRNA gene sequencing and FAME analysis, and used for isoprene degradation. The kinetics of biodegradation is studied using the Michaelis-Menten model. The optimum degradation (80%) with maximum average relative degradation rate was observed at 150 ppm isoprene. The degradation products were also analyzed using FTIR. © 2017 Elsevier Ltd
Molecular ecological perspective of methanogenic archaeal community in rice agroecosystem
(Elsevier B.V., 2017) Singh Alpana; P. Vishwakarma; T.K. Adhya; K. Inubushi; S.K. Dubey
Methane leads to global warming owing to its warming potential higher than carbon dioxide (CO2). Rice fields represent the major source of methane (CH4) emission as the recent estimates range from 34 to 112 Tg CH4 per year. Biogenic methane is produced by anaerobic methanogenic archaea. Advances in high-throughput sequencing technologies and isolation methodologies enabled investigators to decipher methanogens to be unexpectedly diverse in phylogeny and ecology. Exploring the link between biogeochemical methane cycling and methanogen community dynamics can, therefore, provide a more effective mechanistic understanding of CH4 emission from rice fields. In this review, we summarize the current knowledge on the diversity and activity of methanogens, factors controlling their ecology, possible interactions between rice plants and methanogens, and their potential involvement in the source relationship of greenhouse gas emissions from rice fields. © 2017 Elsevier B.V.