Spatial shifts in purple photosynthetic bacterial community composition in paddy soils along the latitude

Purple phototrophic bacteria( PPB) are a diverse group of Proteobacteria that can use sulfur,hydrogen,iron,or organic compounds as electron donors during light harvesting reactions. Because of their metabolic diversity,PPBs are distributed in a wide variety of ecosystems. They participate in,as well as drive,the processes of the carbon cycle in ecosystems. Among terrestrial ecosystems,paddy soils are a preferred PPB habitat. However,gaps exist in our knowledge about PPB community composition in paddy soil and spatial shifts across a large geologic scale. We studied the spatial distribution of PPB in nine representative paddy sites,along a large latitudinal gradient ranging from 28.38[degrees] N to 47.43[degrees] N in China,using PCR-DGGE fingerprinting and phylogenetic analyses. Mechanisms for the spatial shifts in community composition were further elucidated by canonical correspondence analyses and cladograms. It was found that the dominant paddy PPB guilds are purple non-sulfur bacteria,affiliated with alpha and beta branches of Proteobacteria. Soil p H and air temperature( latitude) were the main environmental triggers that influenced PPB community composition in paddy soil. This knowledge will help us to better understand the key species in paddy soil. In addition,this information will contribute to the comprehensive understanding of spatial shifts in the transformation of organic matter along the Chinese latitudinal gradient.