Fuscibacter oryzae gen. nov., sp. nov., a phosphate-solubilizing bacterium isolated from the rhizosphere of rice plant

Abstract

An ovoid to rod shaped, white to brown pigmented, facultative anaerobic, mesophilic, non-phototrophic, Gram-staining-negative, non-motile, multiply by binary fission designated strain KVB23(T), which was isolated from root of rice plant, near Ilsan, South Korea, was investigated for its taxonomic position by polyphasic approach. Optimal growth was found to occur at 30C, at pH 6.5 and in the absence of NaCl on R2A. Phylogenetic analysis based on the 16S rRNA gene sequence of strain KVB23(T) revealed that it formed a distinct lineage, as a separate deep branch within the family Rhodobacteriaceae, with < 96.5% sequence similarity to representatives of the genera Rhodobacter, Xinfangfangia, Tabrizicola, Falsirhodobacter, Haematobacter, Paenirhodobacter, Pseudorhodobacter and Pararhodobacter. Based in 16S rRNA sequences strain KVB23(T) was most closely related to Tabrizicola fusiformis KCTC 62105( T) (96.5%) and Rhodobacter thermarum KCTC 52712( T) (96.2%). The draft genome of strain KVB23(T) was 3.80 bp long with a DNA G + C content of 63.1%. Genome of strain KVB23(T) harboured gene clusters for tryptophan and cobalamin biosynthesis. The strain contained Q-10 as the sole respiratory quinone. The predominant fatty acids were found to consist of C-16:0, C-18:0 and summed feature 8 (comprising C-18:1 omega 7c and / or C-18:1 omega 6). The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, seven unidentified phosphoglycolipids, two unidentified aminophosphoglycolipid, one unidentified glycolipid and four unidentified lipids. Phosphate-solubilizing bacteria have the ability to dissolve insoluble phosphates and enhance the soil fertility. Strain KVB23(T) can solubilize calcium phosphate tribasic. Phosphate solubilizing and tryptophan biosynthesis property of strain KVB23(T) could be a possible factor for the increase in growth of rice plant. Differential phenotypic, chemotaxonomic and genotypic properties, together with the phylogenetic distinctiveness, demonstrated that strain KVB23(T) was found to represent a novel genus in the Rhodobacteriaceae family, for which the name Fuscibacter oryzae gen. nov., sp. nov. is proposed, with the type strain KVB23(T)(= KACC 21711( T) = NBRC 114716( T)).