Taxonomical study of Gordonia sihwensis SPR2, a novel nitrate-reducing bacterium isolated from the wastewater of the lake, Sihwa

Abstract

A nitrate-reducing bacterium strain $SPR2^T$ was isolated from the wastewater of the lake, Sihwa, Korea. The strain was aerobic but could grow under anaerobic condition. It was Gram-positive, exhibited white rough colonies on complex nutrient agar, produced elementary branching hyphae which fragmented into rod/coccus like elements, and showed chemotaxonomic markers which were consistent with the classification of Gordonia, i.e. meso-diaminopimelic acid, arabinose and galactose in whole cell hydrolysates (cell wall chemotype IV), N-glycolylmuramic acid in the peptidoglycan wall, a fatty acid pattern composed of unbranched saturated and monounsaturated fatty acids plus tuberculostearic acid (TBSA), mycolic acids comprising 48-56 carbon atoms, and MK-9 $(H_2)$ as a predominant menaquinone. With 98.2 % and 97.9 % the 16S rDNA sequence of strain $SPR2^T$ showed the highest similarity to those of the type strains Gordonia amicalis DSM $44461^T$ and Gordonia hydrophobica DSM $44015^T$, respectively. These values were far below 99.5 % usually found at the intraspecies level and they were at the same range which separates species at the intrageneric level. The separate phylogenetic position of $SPR2^T$ was supported by differences in fatty acid and mycolic acid composition and in carbon utilization tests which distinguished strain $SPR2^T$ from all known Gordonia species. The combined genotypic and phenotypic data show that strain $SPR2^T$ merits recognition as a new species within genus Gordonia for which the name Gordonia sihwensis is proposed; the type strain is $SPR2^T (= DSM 44576^T)$.