Castellaniella caeni sp. nov., a denitrifying bacterium isolated from sludge of a leachate treatment plant.

A Gram-negative, non-motile, facultatively anaerobic, denitrifying bacterial strain, designated Ho-11(T), was isolated from sludge of a leachate treatment plant and was characterized taxonomically by using a polyphasic approach. The G+C content of the genomic DNA was 63.5 mol%. Strain Ho-11(T) contained ubiquinone Q-8 as the major respiratory lipoquinone and putrescine as the predominant polyamine. The major fatty acids were summed feature 4 (C(16:1)omega7c and/or iso-C(15:0) 2-OH; 29.3%), C(16:0) (28.0%) and summed feature 7 (C(18:1)omega7c, C(18:1)omega9t and/or C(18:1)omega12t; 19.8%). Comparative 16S rRNA gene sequence analysis showed that strain Ho-11(T) belonged to the family Alcaligenaceae, class Betaproteobacteria, and joined the evolutionary radiation enclosed by the genus Castellaniella. 16S rRNA gene sequence similarities between strain Ho-11(T) and the type strains of the two recognized species of the genus, Castellaniella denitrificans DSM 11046(T) and Castellaniella defragrans DSM 12141(T), were 97.8 and 97.4%, respectively. Levels of similarity between strain Ho-11(T) and all other recognized species of the family Alcaligenaceae were below 95.6%. Strain Ho-11(T) exhibited relatively low levels of DNA-DNA relatedness with respect to C. denitrificans DSM 11046(T) (33%) and C. defragrans DSM 12141(T) (28%). On the basis of its phenotypic and genotypic properties together with phylogenetic distinctiveness, strain Ho-11(T) (=KCTC 12197(T)=LMG 23411(T)) should be classified in the genus Castellaniella as the type strain of a novel species, for which the name Castellaniella caeni sp. nov. is proposed.