Tolumonas osonensis sp. nov., isolated from anoxic freshwater sediment, and emended description of the genus Tolumonas

Abstract

A polyphasic taxonomic study was performed on a strain of an unknown Gram-negative, non-motile, saccharolytic, facultatively anaerobic bacterium, strain OCF 7T, isolated from anoxic freshwater sediment. The strain grew optimally at 22 °C and pH 7.5, and was able to grow under strictly anaerobic conditions. Major fermentation products from glucose metabolism were formate, acetate, ethanol and lactate. Comparative 16S rRNA gene sequence analysis indicated that strain OCF 7T was phylogenetically related to the type strain of Tolumonas auensis (97.2 % similarity) within the family Aeromonadaceae of the Gammaproteobacteria. However, OCF 7T did not produce toluene from phenylacetate, phenylalanine, phenoxyacetate, phenylsuccinate or phenylbutyrate in the presence of glucose. Phenol was not produced from tyrosine or phenoxyacetate in the presence of glucose. Dominant fatty acids of this micro-organism included C16 : 0, C18 : 1ω7c and C16 : 1ω7c (and/or iso-C15 : 0 2-OH). Major polar lipids were phosphatidylglycerol and phosphatidylethanolamine, and the respiratory quinone was menaquinone MK-8. The genomic DNA G+C content of strain OCF 7T was 52.1 mol%. Based on phylogenetic and phenotypic evidence, strain OCF 7T should be classified as a representative of a novel species of Tolumonas, for which the name Tolumonas osonensis sp. nov. is proposed; the type strain is OCF 7T ( = DSM 22975T  = ATCC BAA-1908T). An emended description of the genus Tolumonas is also given.