Azonexus caeni sp nov., a denitrifying bacterium isolated from sludge of a wastewater treatment plant

A polyphasic taxonomic study was carried out to determine the taxonomic position of a newly isolated denitrifying bacterium, designated Slu-05(T), which had been isolated from sludge from the main aerobic treatment tanks of a municipal sewage treatment plant. Phylogenetic analysis based on comparative 16S rRNA gene sequencing indicated that strain Slu-05(T) was closely related to Azonexus fungiphilus LMG 19178(T) (96(.)4% sequence similarity), the sole species in the genus Azonexus. Strain Slu-05(T) comprised Gram-negative, motile, non-spore-forming and slightly curved rods. The predominant respiratory lipoquinone was Q-8. The major fatty acids were C-16:1 omega 7c, C-16:0, C-18:1 isomers and C-10:0 3-OH. The G+C content of the genomic DNA was 65.6 mol%. The results of DNA-DNA hybridization (15.6 %) together with phenotypic determination showed that strain Slu-5(T) could be distinguished from A. fungiphilus. Moreover, some phenotypic properties concerning enzyme activity, the substrates utilized as carbon sources and growth conditions distinguish strain Slu-5(T) from A. fungiphilus. On the basis of the results obtained in this study, Slu-05(T) (=DSM 17719(T) =KCTC 12530(T) = CCBAU 10199(T)) is the type strain of a novel species of Azonexus, for which the name Azonexus caeni sp. nov. is proposed.