Changes in methanotrophic community composition after rice crop harvest in tropical soils

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 A mu mol 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.