Dietrich Christiane, Nato Aimé, Bost Bruno, Le Maréchal Pierre, Guyonvarch Armel
CNRS, Orsay F-91405, France.
Université Paris-Sud, IGM, UMR 8621, Orsay F-91405, France.
Microbiology (Reading). 2009 Apr;155(Pt 4):1360-1375. doi: 10.1099/mic.0.022004-0.
Corynebacterium glutamicum is a biotin-auxotrophic bacterium and some strains efficiently produce glutamic acid under biotin-limiting conditions. In an effort to understand C. glutamicum metabolism under biotin limitation, growth of the type strain ATCC 13032 was investigated in batch cultures and a time-course analysis was performed. A transient excretion of organic acids was observed and we focused our attention on lactate synthesis. Lactate synthesis was due to the ldh-encoded l-lactate dehydrogenase (Ldh). Features of Ldh activity and ldh transcription were analysed. The ldh gene was shown to be regulated at the transcriptional level by SugR, a pleiotropic transcriptional repressor also acting on most phosphotransferase system (PTS) genes. Electrophoretic mobility shift assays (EMSAs) and site-directed mutagenesis allowed the identification of the SugR-binding site. Effector studies using EMSAs and analysis of ldh expression in a ptsF mutant revealed fructose 1-phosphate as a highly efficient negative effector of SugR. Fructose 1,6-bisphosphate also affected SugR binding.
谷氨酸棒杆菌是一种生物素营养缺陷型细菌，一些菌株在生物素限制条件下能高效生产谷氨酸。为了了解生物素限制条件下谷氨酸棒杆菌的代谢情况，我们在分批培养中研究了模式菌株ATCC 13032的生长，并进行了时间进程分析。观察到有机酸的短暂排泄，我们将注意力集中在乳酸合成上。乳酸合成是由ldh编码的L-乳酸脱氢酶（Ldh）引起的。分析了Ldh活性和ldh转录的特征。结果表明，ldh基因在转录水平上受SugR调控，SugR是一种多效转录阻遏物，也作用于大多数磷酸转移酶系统（PTS）基因。电泳迁移率变动分析（EMSA）和定点诱变确定了SugR结合位点。使用EMSA进行的效应物研究以及对ptsF突变体中ldh表达的分析表明，1-磷酸果糖是SugR的高效负效应物。1,6-二磷酸果糖也影响SugR结合。
