Pleomorphomonas koreensis sp. nov., a nitrogen-fixing species in the order Rhizobiales

Abstract

A Gram-negative, non-motile, non-spore-forming, rod-shaped bacterium (strain Y9T) was isolated from a contaminated culture of the phototrophic bacterium Rhodopseudomonas palustris, and was investigated using a polyphasic taxonomic approach. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain Y9T belonged to the order Rhizobiales in the Alphaproteobacteria. Comparison of phylogenetic data indicated that it was most closely related to Pleomorphomonas oryzae (98.5 % similarity of 16S rRNA gene sequence), and the phylogenetic distance from any other species of the order Rhizobiales with a validly published name was greater than 7.5 % (i.e. less than 92.5 % similarity). The predominant ubiquinone was Q-10 and the major fatty acids were C18 : 1, C16 : 0, C19 : 0 cyclo ω8c and C18 : 0. The G+C content of genomic DNA of strain Y9T was 65.1 mol%. The results of DNA–DNA hybridization in combination with chemotaxonomic and physiological data demonstrated that strain Y9T represents a novel species within the genus Pleomorphomonas, for which the name Pleomorphomonas koreensis sp. nov. is proposed. The type strain is Y9T (=KCTC 12246T=NBRC 100803T)