Aeromicrobium halocynthiae sp nov., a taurocholic acid-producing bacterium isolated from the marine ascidian Halocynthia roretzi

Abstract

A marine bacterium, strain KME 001(T), was isolated from the siphon tissue of a marine ascidian, Halocynthia roretzi, collected off the coast of Gangneung, Korea. Strain KME 001(T) was a Gram-positive, aerobic, non-spore-forming, rod-shaped and non-motile bacterium. Phylogenetic analysis using 16S rRNA gene sequences revealed that strain KME 001(T) clustered with the genus Aeromicrobium and was closely related to Aeromicrobium ginsengisoli, Aeromicrobium erythreum and Aeromicrobium ponti with 97.7, 97.6 and 97.5% sequence similarities, respectively. The strain was capable of growth at a variety of temperatures (10-42 degrees C) and over a broad pH range (5.0-10.0). NaCl was required for robust growth of the strain. The diagnostic diamino acid of the cell-wall peptidoglycan was LL-diaminopimelic acid. The predominant menaquinone was MK-9(H-4). The predominant fatty acids were C-18:1 omega 9c, C-16:0 and 10-methyl C-18:0. The DNA DNA hybridization analyses showed that DNA-DNA relatedness values between strain KME 001(T) and its nearest neighbours, A. ginsengisoli KCTC 19207(T), A. erythreum KCCM 41104(T) and A. ponti KACC 20565(T), were 49.6, 57.1 and 63.5%, respectively. The DNA G+C content of strain KME 001(T) was 75.9 mol%. Chemical investigation of the liquid culture medium of strain KME 001(T) led to the isolation of taurocholic acid as a major secondary metabolite. On the basis of phylogenetic and phenotypic data, strain KME 001(T) is classified as representing a novel species of the genus Aeromicrobium, for which the name Aeromicrobium halocynthiae sp. nov. is proposed. The type strain is KME 001(T) (=JCM 15749(T)=KCCM 90079(T)).