Identification of moderately halophilic strain DTY1 and study of its halotolerant mechanism
中度嗜盐菌DTY1的鉴定及其耐盐机制的初步分析

A bacterial strain DTY1 was isolated from Caragana rhizosphere in Wuzhai, Shanxi. It was identified as Bacillus alcalophilus according to its morphological, physiological, biochemical characters and the sequence analysis of the 16S rDNA. The growth salinity of strain DTY1 was between 0 - 1.2mol/L NaCl. The optimum growth temperature and pH was 32 degrees C and 7 - 10, respectively. Strain DTY1 could accumulate 1.40mg/g ectoine in LB medium containing 0.17mol/L NaCl quantified by high-performance liquid chromatography. And the yield of ectoine improved as increasing of medium salinity. In this study, an ectB gene which potentially encoded a L-2, 4-diaminobutyric acid transaminase enzyme and involved in biosynthesis of ectoine was cloned by PCR-mediated screening from the genomic library of strain DTY1. Nucleotide sequencing indicated that the ectB gene contains 1284bp, and is predicated to encode a peptide of 427 amino acids, which shares 81% identity to that of the EctB of B. halodurans C-125. One potential sigma70 promoter and a 23bp palindromic sequence were found to locate at the upstream of ectB gene.