A facultatively alkaliphilic, lactic-acid-producing and halophilic strain, designated SG103(T), was isolated from a fermented Polygonum indigo (Polygonum tinctorium Lour.) liquor sample for dyeing prepared in a laboratory. 16S rRNA gene sequence phylogeny suggested that SG103(T) is a member of the genus Gracilibacillus with the closest relatives being 'Gracilibacillus xinjiangensis' J2 (similarity: 97.06 %), Gracilibacillus thailandensis TP2-8(T) (97.06 %) and Gracilibacillus halotolerans NN(T) (96.87 %). Cells of the isolate stained Gram-positive and were facultatively anaerobic straight rods that were motile by peritrichous flagella. The strain grew at temperatures between 13 and 48 °C with the optimum at 39 °C. It grew in the range pH 7-10 with the optimum at pH 9. The isoprenoid quinone detected was menaquinone-7 (MK-7) and the DNA G+C content was 41.3 mol%. The whole-cell fatty acid profile mainly (>10 %) consisted of iso-C15 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. Unlike other reported species of the genus Gracilibacillus, the strain lacked diphosphatidylglycerol as a major polar lipid. DNA-DNA hybridization experiments with strains exhibiting greater than 96.87 % 16S rRNA gene sequence similarity, 'G. xinjiangensis' J2, G. thailandensis TP2-8(T) and G. halotolerans NN(T), revealed 2±4 %, 4±9 % and 3±2 % relatedness, respectively. On the basis of the differences in phenotypic and chemotaxonomic characteristics, and the results of phylogenetic analyses based on 16S rRNA gene sequences and DNA-DNA relatedness data from reported species of the genus Gracilibacillus, strain SG103(T) merits classification as a members of a novel species, for which the name Gracilibacillus alcaliphilus sp. nov. is proposed. The type strain is SG103(T) ( = JCM 17253(T) = NCIMB 14683(T)).
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