中度嗜盐菌DTY1的鉴定及其耐盐机制的初步分析

Identification of moderately halophilic strain DTY1 and study of its halotolerant mechanism

菌株DTY1分离自山西省五寨县柠条种植区盐碱土壤，可在0-1．2mol／L NaCl的浓度培养基上生长，最适生长温度32℃，最适pH7-10。通过形态观察，生理生化测定与16S rDNA序列分析，将该菌株鉴定为嗜碱芽孢杆菌（Bacillus alcalophilus）。高压液相色谱分析，DTY1菌株在常规LB培养液中能够产生1．40mg／g四氢嘧啶，且在最适盐浓度条件下，盐浓度越高单位干重菌体所产生的四氢嘧啶含量越高。通过PCR介导的方法从DTY1的基因组文库中克隆到四氢嘧啶合成基因ectB。该基因长度为1284bp，编码427个氨基酸的肽链。此肽链与B．halodurans C-125 （BABO4638）中二氨基丁酸氨基转移酶同源性达81％。ectB基因可能存在典型的σ^70启动子，而且在启动子间有一段明显的23bp的回文序列。

A bacterial strain DTY1 was isolated from Caragana rhizosphere in Bacillus alcalophilus according to its morphological, physiological, biochemical Wuzhai, Shanxi. characters and the It was identified as 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℃ 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 σ^70 promoter and a 23bp palindromic sequence were found to locate at the upstream of ectB gene.