Halolactibacillus halophilus gen. nov., sp. nov. and Halolactibacillus miurensis sp. nov., halophilic and alkaliphilic marine lactic acid bacteria constituting a phylogenetic lineage in Bacillus rRNA group 1

Abstract

Eleven novel strains of marine-inhabiting lactic acid bacteria that were isolated from living and decaying marine organisms collected from a temperate area of Japan are described. The isolates were motile with peritrichous flagella and non-sporulating. They lacked catalase, quinones and cytochromes. Fermentation products from glucose were lactate, formate, acetate and ethanol. Lactate yield as percentage conversion from glucose was affected by the pH of the fermentation medium: ∼55 % at the optimal growth pH of 8·0, greater than ∼70 % at pH 7·0 and less than ∼30 % at pH 9·0. The molar ratio of the other three products was the same at each cultivation pH, approximately 2 : 1 : 1. Carbohydrates and related compounds were aerobically metabolized to acetate and pyruvate as well as lactate. The isolates were slightly halophilic, highly halotolerant and alkaliphilic. The optimum NaCl concentration for growth was 2·0–3·0 % (w/v), with a range of 0–25·5 %. The optimum pH for growth was 8·0–9·5, with a range of 6·0–10·0. The G+C content of the DNA was 38·5–40·7 mol%. The isolates constituted two genomic species (DNA–DNA relatedness of less than 41 %) each characterized by sugar fermentation profiles. The cell-wall peptidoglycan of both phenotypes containedmeso-diaminopimelic acid. The major cellular fatty acids were C16 : 0and a-C13 : 0. Comparative sequence analysis of the 16S rRNA genes revealed that these isolates represent novel species constituting a phylogenetic unit outside the radiation of typical lactic acid bacteria and an independent line of descent within the group composed of the halophilic/halotolerant/alkaliphilic and/or alkalitolerant species inBacillusrRNA group 1, with 94·8–95·1 % similarity to the genusParaliobacillus, 93·7–94·1 % to the genusGracilibacillusand 93·8–94·2 % toVirgibacillus marismortui. On the basis of possession of physiological and biochemical characteristics common to typical lactic acid bacteria withinBacillusrRNA group 1, chemotaxonomic characteristics and phylogenetic independence, a new genus and two species,Halolactibacillus halophilusgen. nov., sp. nov. andHalolatibacillus miurensissp. nov., are proposed. The type strains areHalolactibacillus halophilusM2-2T(=DSM 17073T=IAM 15242T=NBRC 100868T=NRIC 0628T) (G+C content 40·2 mol%) andHalolactibacillus miurensisM23-1T(=DSM 17074T=IAM 15247T=NBRC 100873T=NRIC 0633T) (G+C content 38·5 mol%).