Catellibacterium nectariphilum gen. nov., sp. nov., which requires a diffusible compound from a strain related to the genus Sphingomonas for vigorous growth

A bacterial strain, designated AST4T, was isolated from activated sludge. The bacterium did not show significant growth on nutrient broth, but growth was clearly stimulated by addition of supernatant from other bacterial cultures. Culture filtrate of a strain related to the genus Sphingomonas in particular increased the cell yield and growth rate of strain AST4T. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain AST4T is located within the ‘Rhodobacter group’ in the α-3 subclass of Proteobacteria, but is clearly distant from related genera in this group such as Paracoccus, Rhodobacter and Rhodovulum. Strain AST4T is a Gram-negative, non-motile, rod-shaped (0·6–0·8×1·3–2·0 μm) and aerobic bacterium. It was not able to reduce nitrate to nitrite or N2. No phototrophic growth was observed. Optimal growth occurred at 30 °C and pH 6·5–7·5. The dominant cellular fatty acid in the isolate was C18 : 1 cis11. Ubiquinone-10 was the major respiratory quinone. The G+C content was 64·5 mol% (by HPLC). Based on the phylogenetic and phenotypic traits, the name Catellibacterium nectariphilum gen. nov., sp. nov. is proposed for this isolate; the type strain is AST4T (=NBRC 100046T=JCM 11959T=DSM 15620T).