Alkalibacterium gilvum sp nova, slightly halophilic and alkaliphilic lactic acid bacterium isolated from soft and semi-hard cheeses

Nine novel strains of halophilic and alkaliphilic lactic acid bacteria isolated from European soft and semi-hard cheeses by using a saline, alkaline medium (7 % NaCl, pH 9.5) were taxonomically characterized. The isolates were Gram-positive, non-sporulating and non-motile. They lacked catalase and quinones. In anaerobic cultivation condition, lactate was produced from glucose with the production of formate, acetate and ethanol with a molar ratio of approximately 2:1:1. In aerobic cultivation condition, acetate and lactate were produced from glucose. The isolates were slightly halophilic, highly halotolerant and alkaliphilic. The optimum NaCl concentration for growth ranged between 2.0 % and 5.0 %(w/v), with a growth range of 0-1% to 15-17.5 %. The optimum pH for growth ranged between 8.5 and 9.5, with a growth range of 7.0-7.5 to 9.5-10.0. Comparative sequence analysis of the 16S rRNA genes revealed that the isolates occupied a phylogenetic position within the genus Alkalibacterium, showing the highest similarity (98.2 %) to Alkalibacterium kapii T22-1-2(T). The isolates constituted a single genomic species with the DNA-DNA hybridization values of 79-100% among the isolates and those below 29% between the genomic species and other members of Alkalibacterium, from which the isolates were different in motility and flagellation, growth responses to NaCl concentrations and pH, and profiles of sugar fermentation. The G+C content of the DNA were between 36.0 and 37.6 %. The cell-wall peptidoglycan was type A4 beta, Orn-D-Asp. The major components of cellular fatty acids were C-14:0, C-16:0 and C-16:1 omega 9C. On the bases of phenotypic characteristics and genetic distinctness, the isolates are classified as a new species within the genus Alkalibacterium, for which the name Alkalibacterium gilvum sp. nov. is proposed. The type strain is 3AD-1(T) (DSM 25751(T)=JCM 18271(T)).