Andresen P A, Kaasen I, Styrvold O B, Boulnois G, Strøm A R
Institute of Fisheries, University of Tromsø, Norway.
J Gen Microbiol. 1988 Jun;134(6):1737-46. doi: 10.1099/00221287-134-6-1737.
An analysis of the bet genes governing the osmoregulatory choline-glycine betaine pathway of Escherichia coli was performed. A 9 kb BamHI fragment, located 30 to 39 kb counterclockwise of the EcoRI site of lacZ, coded for all known Bet activities. The following genes were identified: the betA gene for the choline dehydrogenase, the betB gene for the betaine aldehyde dehydrogenase, and the betT gene or operon for the high-affinity choline transport. The betB and the betT genes were named in this paper, and the clockwise gene order was shown to be betA,B,T. Subcloning gave plasmids which expressed each of the three Bet activities separately. The cloned bet genes remained osmotically regulated, indicating the existence of several osmotically regulated promoters in the bet region. Salmonella typhimurium, which carried the bet region of E. coli in the broad-host-range vector pRK293 expressed the three Bet activities and displayed increased osmotic tolerance in the presence of choline.
对大肠杆菌中调控渗透调节胆碱 - 甘氨酸甜菜碱途径的bet基因进行了分析。一个位于lacZ的EcoRI位点逆时针方向30至39 kb处的9 kb BamHI片段编码了所有已知的Bet活性。鉴定出了以下基因：编码胆碱脱氢酶的betA基因、编码甜菜碱醛脱氢酶的betB基因以及编码高亲和力胆碱转运的betT基因或操纵子。本文对betB和betT基因进行了命名，并且显示顺时针方向的基因顺序为betA、B、T。亚克隆得到了分别表达三种Bet活性的质粒。克隆的bet基因仍受渗透压调节，这表明在bet区域存在多个受渗透压调节的启动子。携带大肠杆菌bet区域的鼠伤寒沙门氏菌在广宿主范围载体pRK293中表达了三种Bet活性，并且在胆碱存在的情况下表现出更高的渗透压耐受性。
