Pleomorphomonas oryzae gen. nov., sp. nov., a nitrogen-fixing bacterium isolated from paddy soil of Oryza sativa

Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-Ku, Tokyo 113-0032, Japan Correspondence Cheng-Hui Xie aa37116{at}mail.ecc.u-tokyo.ac.jp Five strains of free-living diazotrophs isolated from rice were characterized by using a polyphasic approach. The strains were found to be very closely related, with 99–100 % 16S rRNA gene sequence similarity and DNA–DNA hybridization values greater than 70 %, suggesting that they represent a single species. When compared with other recognized species, they showed not more than 93 and 89 % similarity for the 16S rRNA and nifH gene sequences, respectively. Phylogenetic distances showed that these isolates were distinct from other taxa within the - Proteobacteria . Chemotaxonomic characteristics of these isolates included the DNA G+C content (62·1–63·1 mol%), the major quinone system (Q-10), predominant fatty acids (18 : 1 7 c , cyclo 19 : 0 8 c and 16 : 0) and major hydroxy fatty acids (14 : 0 3-OH, 18 : 0 3-OH and 16 : 0 3-OH). Based on phylogenetic and phenotypic analyses, these isolates are considered to represent a novel genus and species, for which the name Pleomorphomonas oryzae gen. nov., sp. nov. is proposed. The type strain is F-7 T (=IAM 15079 T =ATCC BAA-940 T =DSM 16300 T ). Abbreviations: PHB, poly- -hydroxybutyrate Published online ahead of print on 7 January 2005 as DOI 10.1099/ijs.0.63406-0. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains F-7 T , B-24, B-4, B-18 and B-32 are AB159680 and AB159682 –AB159685, respectively, and for the nifH gene sequences they are AB161454 , AB182912 , AB159683 , AB182911 and AB182913 , respectively. A neighbour-joining tree based on nifH gene sequences showing the position of the novel strains is available as supplementary material in IJSEM Online.