Metagenomic analysis of the microbial community in the rhizosphere of rice in Yuanyang Terrace

Terraces are known as areas that historically have been planted with rice for more than 1400 years. However, there are few reports about the characteristics of the local soil microbes. For this reason, Yuanyang terrace soil (YTS) characteristics and analytical metagenome analysis were investigated using chemical methods and Illumina HiSeq techniques. In this study, YTS samples had a higher content of organic matter than Greenhouse soil (GHS). Proteobacteria and Acidobacteria, consecutively, were the two dominant phyla accounting for almost 70% of the total sequence data. Within Proteobacteria, Geobacter and Bradyrhizobium accounted for an average of 11% and 4% of the GHS samples, while in the YTS samples they accounted for 4% and 0% (of the total sequences). The other substantial genera in the YTS samples were Methanoculleus (2%) and Methanosaeta (2%), which function in methane production and inhibit methane synthesis. The relative abundances of genes concerned in nitrogen absorption were higher in the GHS trails than in the YTS samples, particularly for the napA gene. Our results demonstrate that the YTS samples had an apparent higher relative abundance of genes involved in CO2 reduction and methane production which could provide protection to rice against attacks by pathogens.