中文摘要：

基于gshB基因同源性分析设计引物，从采集的菜园地土壤中分离到1株具有谷胱甘肽（GSH）合成能力的乳酸乳球菌菌株CCSYU10100。测定了该菌株的16SrDNA序列并根据16SrDNA序列构建了系统发育树，结果显示该菌株与乳酸乳球菌乳脂亚种在进化关系上的地位最近。电镜分析表明，菌株CCSYU10100与乳酸乳球菌的形态特征基本一致。因此认为菌株CCSYU10100属于乳酸乳球菌乳脂亚种，命名为乳酸乳球菌乳脂亚种CCSYU10100。HPLC法鉴定出该菌株胞内除GSH外，还存在半胱氨酸-甘氨酸。乳酸乳球菌CCSYU10100的部分gshB基因与假单胞菌属的gshB基因高度同源，这是gshB基因在乳酸乳球菌中、甚至是革兰氏阳性菌中的首次发现。

英文摘要：

A bacterial strain that produces glutathione（GSH） was screened from vegetable garden soil based on a polymerase chain reaction （PCR） protocol which could rapidly and specifically identify the gshB gene coding for GSH synthetase. Phylogenetic analysis based on 16S rDNA revealed that this strain belongs to L. lactis ssp. cremoris. Scanning deotren microscope analysis indiczated that its morpholegy characteristics were most consistent with Lactococcus/actis. So we suggested that the strain belonged to L. lactis ssp. cremoris and named L. lactis CCSYU10100. The intracellular level of GSH in stationary-phase cells of strain CCSYU10100 grown aerobically in chemically-defined medium was 2.39 ± 0.21 nmol/mg protein. Other than GSH, cysteinylglycine was identified by HPLC. The partial gshB gene sequence and the deduced amino acid sequence of strain CCSYU10100 were highly similar with that of Pseudomonas among different microorganisms, which indicated that strain CCSYU10100 probably possesses independent gshB gene. Noticeably, the GC content of the partial gshB gene of strain CCSYU10100 was 61.55%, and the GC content of whole genome of L. lactis is 35% - 40%, which seggusted that the gshB gene might not be an inherent part of strain CCSYU10100.Considering Pseudomonasfluorescens exists in the soil widely, it was speculated that the origin of gshB gene of strain CCSYU10100 was from Pseudomonas fluorescens by lateral gene transfer. The deduced amino acid sequence of strain CCSYU 10100 contained two conserved domain, i.e., prekaryotic GSH synthetase, N-termlnal domain （2^nd 58^th amino acid residues） （identities 44.5% ） and prokaryotic GSH synthetase, ATP-binding domain（61^st -221^s1 amino acid residues） （identities 93.4% ）. To our knowledge, this is the first report showing gshB gene exists in Lactococcus,lactis even in Gram-positive bacteria.