Acidovorax radicis sp. nov., a wheat-root-colonizing bacterium

Abstract

Strain N35T was isolated from surface-sterilized wheat roots and is a Gram-negative, aerobic, motile straight rod. Strain N35T tested oxidase-positive and catalase-negative and grew optimally at pH 7.0, 30 °C and in the absence of NaCl. 16S rRNA gene sequence analysis showed over 97 % sequence similarity to strains of the environmental species Acidovorax delafieldii, A. facilis, A. defluvii, A. temperans, A. caeni and A. soli, as well as Acidovorax valerianellae, A. anthurii and Simplicispira metamorpha. DNA–DNA hybridization between strain N35T and phylogenetically closely related type strains was 25.3–55.7 %, which clearly separates the strain from these closely related species. Additionally, phenotypic properties, such as substrate metabolism profiles as determined by a Biolog GN2 assay and cell-wall fatty acid profiles, particularly contents of the fatty acids C16 : 0, C16 : 1ω7c/t, C17 : 0, C17 : 0 cyclo, C18 : 0 cyclo and C19 : 0 cyclo, facilitated the differentiation of the newly isolated strain N35T from its closest relatives. The isolate underwent phenotypic variation at high frequency in laboratory media. The DNA G+C content was 64.9 mol%. We propose that strain N35T is classified as a representative of a novel species within the genus Acidovorax, and suggest the name Acidovorax radicis sp. nov. The type strain is strain N35T ( = DSM 23535T  = LMG 25767T).