Agriculturally relevant microbial community structure in long-term fertilized paddy soils as revealed by phospholipid fatty acid (PLFA) and pyrosequencing analyses

Evidence linking the direct impact of fertilization on diversity, function and phylogeny of N-fixing and P-solubilizing bacteria in rice ecosystem is lacking. This study using phospholipid fatty acid (PLFA) and 454 pyrosequencing analyses was conducted in long-term fertilized (NP, NK, PK, NPK, compost, NPK + compost) paddy field soil, the objective being to examine the community structure of the functionally important beneficial soil microbial communities. Maximum total PLFAs were observed in organic fertilizer treatments, viz. compost (881.5 +/- 11.1 nmol g(-1)) and NPK + compost (866.5 +/- 10.8n mol g(-1)). Pyrosequencing revealed that the overall bacterial and eukaryal compositions at phyla level were not significant for all treatments, while the distribution of each phyla differed. Specifically, the major classified bacterial phyla for all treatments were Proteobacteria, Actinobacteria, Cyanobacteria and Firmicutes. Supported by the high throughput sequencing approach we hereby propose that the mechanism of N and P cycling under long-term balanced fertilization in a rice ecosystem is largely governed by microbes, notably by the free living N-fixing and/or P solubilizing heterocystous and/or non-heterocystous cyanobacteria, autotrophic bacteria and heterotrophic bacteria. The current study thus proposes that balanced fertilizers may be used without detrimental effects on rice soils in the long-term.