Mesorhizobium denitrificans sp. nov., a novel denitrifying bacterium isolated from sludge

Abstract

A Gram-stain-negative, non-spore-forming, facultative, rod-shaped bacterium (designated LA-28^T) was isolated from a sludge sample from a wastewater treatment plant in Hanam city, Republic of Korea. On the basis of 16S rRNA gene sequencing, strain LA-28^T clustered with species of the genus Mesorhizobium and appeared closely related to M. jarvisii LMG 28313^T (96.8%), M. waimense ICMP 19557^T (96.7%), and M. huakuii LMG 14107^T (96.7%). Growth occurs at 18-40°C on R2A medium in the presence of 1-4% NaCl (w/v) and at pH 6-8. The DNA G+C content was 61.2 mol%, and the predominant quinone was ubiquinone-10 (Q-10). The major cellular fatty acids (> 5%) were C_16:0, C_19:0ω8c cyclo, C_18:1ω7c 11-methyl, and C_18:1ω7c and/or C_18:1ω6c (summed feature 8). Major polar lipids were phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidyl-N-methylethanolamine (PME), and phosphatidylcholine (PC). Physiological and biochemical characteristics indicated that strain LA-28^T represents a novel species of the genus Mesorhizobium, for which the name Mesorhizobium denitrificans sp. nov. is proposed. The type strain is LA-28^T (= KACC 19675^T = LMG 30806^T).

Keywords: 16S rRNA gene sequence; Mesorhizobium denitrificans; polyphasic taxomony; sludge.