Oerskovia flava sp. nov., a deoxynivalenol (DON)-degrading actinomycete isolated from the rhizosphere soil of long-term continuous cropping cucumber

Abstract

The deoxynivalenol (DON)-degrading bacterium JB1-3-2 ^T was isolated from a rhizosphere soil sample of cucumber collected from a greenhouse located in Zhenjiang, Eastern China. The JB1-3-2 ^T strain is a Gram-stain-positive, nonmotile and round actinomycete. Growth was observed at temperatures between 15 and 40 ℃ (optimum, 35 ℃), in the presence of 15% (w/v) NaCl (optimum, 3%), and at pH 3 and 11 (optimum, 7). The major cellular fatty acids identified were anteiso-C_15:0, iso-C_16:0 and anteiso-C_17:0. Genome sequencing revealed a genome size of 4.11 Mb and a DNA G + C content of 72.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the JB1-3-2 ^T strain was most closely related to type strains of the Oerskovia species, with the highest sequence similarity to Oerskovia turbata NRRL B-8019 ^T (98.2%), and shared 98.1% sequence identity with other valid type strains of this genus. Digital DNA‒DNA hybridization (dDDH) and average nucleotide identity (ANI) showed 21.8–22.2% and 77.2–77.3% relatedness, respectively, between JB1-3-2 ^T and type strains of the genus Oerskovia. Based on genotypic, phylogenetic, chemotaxonomic, physiological and biochemical characterization, Oerskovia flava, a novel species in the genus Oerskovia, was proposed, and the type strain was JB1-3-2 ^T (= CGMCC 1.18555 ^T = JCM 35248 ^T). Additionally, this novel strain has a DON degradation ability that other species in the genus Oerskovia do not possess, and glutathione-S-transferase was speculated to be the key enzyme for strain JB1-3-2 ^T to degrade DON.