Rhodanobacter spathiphylli sp. nov., a gammaproteobacterium isolated from the roots of Spathiphyllum plants grown in a compost-amended potting mix

Three Gram-negative, yellow-pigmented strains were isolated from the rhizospheres of Spathiphyllum plants grown in a compost-amended potting mix. The strains showed biological control activity towards the root-rot plant pathogen Cylindrocladium spathiphylli, and were characterized to determine their taxonomic position. Cells of the strains were non-motile rods, and the strains were oxidase- and catalase-positive and unable to ferment most sugars tested. The three strains showed differences in growth temperature range, optimal growth temperature and some biochemical reactions. The majority of the fatty acids were branched, and large amounts of 15 : 0 iso and 17 : 1 iso omega9c were present. The 16S rRNA gene sequence (1,497 bp) of strain B39(T) showed the highest level of similarity (98.5 %) to that of Rhodanobacter fulvus IAM 15025(T), followed by Rhodanobacter lindaniclasticus LMG 18385(T) (96.0 %; strain no longer extant), Dyella koreensis CCUG 50883(T) (96.4 %), Dyella japonica DSM 16301(T) (96.3 %), Frateuria aurantia LMG 1558(T) (96.2 %) and Fulvimonas soli LMG 19981(T) (95.9 %). Less than 90 % 16S rRNA gene sequence similarity was observed for other members of the Gammaproteobacteria. The mean DNA-DNA reassociation value for the three strains was 100 % and was 25 % when the strains were compared with DNA from R. fulvus LMG 23003(T). The strains had a mean DNA G+C content of 67.6 mol%. On the basis of their phylogenetic, genomic and phenotypic properties, the three strains represent a novel species within the genus Rhodanobacter, for which the name Rhodanobacter spathiphylli sp. nov. is proposed. The type strain is strain B39(T) (=LMG 23181(T)=DSM 17631(T)).