Gracilibacillus lacisalsi sp. nov., a halophilic Gram-positive bacterium from a salt lake in China

Abstract

Two Gram-positive, motile, rod-shaped, halophilic bacteria showing optimum growth at 5-7 % (w/v) NaCl were isolated from a salt lake, Xin-Jiang Province, China. The strains, designated BH312 T and BH314, grew in the presence of 1-18 % (w/v) NaCl and at temperatures of 15-50 6C (optimum: 40 6C) and pH values of 5.5-10.0 (optimum: pH 7.5-8.0). The major cellular fatty acids were anteiso-C 15 : 0 , iso-C 15 : 0 and anteiso-C 17 : 0 . The DNA G+C content was 38.8-39.0 mol% and the predominant lipoquinone was MK-7. The major cellular phospholipids were phosphatidylglycerol, diphosphatidylglycerol and two unidentified phospholipids. Phylogenetic analyses based on 16S rRNA gene sequences showed that the isolates formed a cluster with Gracilibacillus orientalis XH-63 T within the genus Gracilibacillus. The levels of 16S rRNA gene sequence similarity with closely related type strains were lower than 96.2 %. On the basis of phylogenetic, phenotypic and chemotaxonomic properties, the isolates represent a novel species of the genus Gracilibacillus for which the name Gracilibacillus lacisalsi sp. nov. is proposed. The type strain is BH312 T (5KCTC 13129 T 5DSM 19029 T ).Moderately halophilic bacteria that grow optimally in media containing 3-15 % (w/v) NaCl are widely distributed in different marine environments and are made up of very heterogeneous physiological groups taxonomically, including both Gram-positive and Gram-negative microorganisms (Ventosa et al., 1998;Oren, 2002;Jeon et al., 2005a;Lim et al., 2005). Aerobic, spore-forming, halophilic, Gram-positive rods that were originally assigned to the genus Bacillus are also very diverse taxonomically and they form several phylogenetically distinct lineages (Ash et al., 1991;Stackebrandt & Liesack, 1993;Nielsen et al., 1994;Jeon et al., 2005b). Among them, the genus Gracilibacillus was first proposed by Wainø et al. (1999) to accommodate Gracilibacillus halotolerans, isolated from the Great Salt Lake, Utah (USA), and Gracilibacillus dipsosauri, transferred from Bacillus dipsosauri. Currently, the genus includes only four species: G. halotolerans, G. dipsosauri (Wainø et al., 1999), G. orientalis (Carrasco et al., 2006) and G. boraciitolerans (Ahmed et al., 2007). In the course of screening sediment of Ai-Ding Lake, Xin-Jiang Province, China, to isolate halophilic bacteria, two aerobic, Gram-positive, moderately halophilic bacteria, strains BH312 T and BH314, were isolated. Ai-Ding Lake (42 u 329 100-42 u 499 130 N 89 u 109 320-89 u 549 320 E) is located in the most arid area of China, where evaporation is significantly higher than precipitation. The lake is the lowest point in China (154 m below sea-level) and has been a target area for the study of halophilic microorganisms for many years. Water is largely supplied from the nearby glacier of Tian-Shan Mountain. Ai-Ding Lake is a typical chloride-sulfate saline lake with a slightly alkaline pH (7.2-7.6) and a salt concentration of 20-26 % (w/v). The content of Mg 2+ and Ca 2+ in the brine is very low. On the basis of phy...

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Microbial culturomics unravels the halophilic microbiota repertoire of table salt: description of Gracilibacillus massiliensis sp. nov.

“…This genus includes 12 species ( www.bacterio.net ) described with valid published names ( 7 ). Members of the genus Gracilibacillus are salty environmental bacteria isolated most often from soil ( 8 ), food ( 9 ), lakes and salty sea water ( 10 , 11 ).…”