Ideonella azotifigens sp nov., an aerobic diazotroph of the Betaproteobacteria isolated from grass rhizosphere soil, and emended description of the genus Ideonella

Strain 1a22(T), a nitrogen-fixing bacterium, was isolated from soil associated with the rhizosphere of a perennial grass growing in a fallow agricultural field in Ithaca, New York, USA. Analysis of the 16S rRNA gene sequence placed the strain in the Rubrivivax-Roseateles-Leptothrix-Azohydromonas-Aquincola-Ideonella branch of the Betaproteobacteria and the closest characterized relative was the type strain of Ideonella dechloratans (97.7 % 16S rRNA sequence similarity). Cells of strain 1a22(T) were Gram-negative, motile, straight rods, which formed polyhydroxybutyrate-like granules and were positive for oxidase and weakly positive for catalase. Cells were chemo-organotrophic, unable to grow by reduction of chlorate or nitrate and grew exclusively through aerobic respiration. Growth with mannitol on I solid media caused the strain to produce copious amounts of slime. The G + C content of the genomic DNA was 67.4 mol%. The major cellular fatty acids were C-16:1 cis-9 and C-16:0 and cells contained significant amounts of the hydroxy fatty acids C-10:0 3-OH, C-12:0 2-OH and C-12:0 3-OH. Based on DNA-DNA hybridization studies, 16S rRNA gene sequence analysis, fatty acid analysis, and morphological and physiological characteristics, strain 1a22(T) represents a novel species in the genus Ideonella, for which the name Ideonella azotifigens sp. nov. is proposed. The type strain of Ideonella azotifigens is 1a22(T) (=JCM 15503(T) = DSM 21438(T)).