Gracilibacillus pellucidus sp. nov., a moderately halophilic bacterium isolated from saline soil in Xinjiang province, China

Abstract

A motile, Gram-positive, moderately halophilic, catalase-positive and oxidase-negative, obligate aerobic, slender rod-shaped bacterium, strain S3-1-1^T was isolated from the plant rhizosphere soil in saline soil of Xinjiang Uygur Autonomous Region. Strain S3-1-1^T grew in the presence of 1–21% NaCl and at pH 7.0–9.0, with optimum growth at 3% NaCl and pH 7.5. It grew at 16–45 °C, with optimum growth at 40 °C.Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S3-1-1^T should be placed within the genus Gracilibacillus and formed a separate branch. It exhibited highest similarities to Gracilibacillus ureilyticus MF38^T (sequence similarity 97.7%), Gracilibacillus massiliensis Awa-1^T (sequence similarity 97.5%), Gracilibacillus xinjiangensis J2^T (sequence similarity 97.4%) and Gracilibacillus salitolerans SCU50^T (sequence similarity 97.4%). Genomic comparisons revealed that strain S3-1-1^T shares closest phylogenetic relationships with Gracilibacillus saliphilus YIM 91119^T (ANI 77.4%, AAI 78.4%), Gracilibacillus thailandensis TP2-8T (ANI 77.2%, AAI 78.3%), and Gracilibacillus salitolerans SCU50^T (ANI 77.3%, AAI 78.1%). However, the digital DNA-DNA hybridization (19.3–22.1%), average nucleotide identity (71.1–77.4%), and average amino acid identity (66.9–78.6%) values all fell below the recommended thresholds for species delineation, supporting its novel taxonomic status. The major cellular fatty acids were anteiso-C_15:0, C_16:0, iso-C_15:0, and anteiso-C_17:0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and aminophospholipids. On the basis of their phenotypic, physiological, biochemical and phylogenetic characteristics, S3-1-1^T represented a novel species of the genus Gracilibacillus, for which the name Gracilibacillus pellucidus sp. nov. is proposed, with S3-1-1^T (= JCM 36422^T = GDMCC 1.4017^T) as the type strain.