Megasphaera hexanoica sp nov., a medium-chain carboxylic acid-producing bacterium isolated from a cow rumen

Abstract

Strain MHT, a strictly anaerobic, Gram-stain-negative, non-spore-forming, spherical coccus or coccoid-shaped microorganism, was isolated from a cow rumen during a screen for hexanoic acid-producing bacteria. The microorganism grew at 30-40 degrees C and pH 5.5-7.5 and exhibited production of various short-and medium-chain carboxylic acids (acetic acid, butyric acid, pentanoic acid, isobutyric acid, isovaleric acid, hexanoic acid, heptanoic acid and octanoic acid), as well as H-2 and CO2 as biogas. Phylogenetic analysis based on 16S rRNA gene sequencing demonstrated that MHT represents a member of the genus Megasphaera, with the closest relatives being Megapsphaera indica NMBHI-10(T) (94.1% 16S rRNA sequence similarity), Megasphaera elsdenii DSM 20460(T) (93.8 %) and Megasphaera paucivorans DSM 16981(T) (93.8 %). The major cellular fatty acids produced by MHT included C-12 : 0, C-16 : 0, C(18 : 1)cis 9, and C-18 : 0, and the DNA G+C content of the MHT genome is 51.8 mol%. Together, the distinctive phenotypic and phylogenetic characteristics of MHT indicate that this microorganism represents a novel species of the genus Megasphaera, for which the name Megasphaera hexanoica sp. nov. is herein proposed. The type strain of this species is MHT (=KCCM 43214(T)=JCM 31403(T)).