Lemos José A C, Brown Thomas A, Abranches Jacqueline, Burne Robert A
Department of Oral Biology, University of Florida College of Dentistry, 1600 SW Archer Road, Gainesville, FL 32610-0424, USA.
FEMS Microbiol Lett. 2005 Dec 15;253(2):251-7. doi: 10.1016/j.femsle.2005.09.045. Epub 2005 Oct 13.
Two pairs of genes were identified in Streptococcus mutans with similarity to relBE and mazEF toxin-antitoxin (TA) modules of Escherichia coli. Transcription of mazEF and relBE was repressed by amino acid starvation, and relBE expression was repressed by low pH. Mutants lacking MazF, RelE, or both toxins (MRT1) grew in broth media and formed biofilms as well as the parent. Biofilm populations of MRT1 were more resistant to acid killing than the parent or single mutants. MRT1 also exhibited a longer diauxie during growth on glucose and inulin and displayed decreased phosphoenolpyruvate:sugar phosphotransferase activity. This is the first report that demonstrates a physiological role for TA modules in Gram-positive bacteria.
在变形链球菌中鉴定出两对与大肠杆菌的relBE和mazEF毒素-抗毒素（TA）模块相似的基因。mazEF和relBE的转录受氨基酸饥饿抑制，relBE的表达受低pH抑制。缺乏MazF、RelE或两种毒素的突变体（MRT1）在肉汤培养基中生长并形成生物膜，与亲本相同。MRT1的生物膜群体比亲本或单突变体对酸杀伤更具抗性。MRT1在葡萄糖和菊粉上生长时还表现出更长的二次生长现象，并且磷酸烯醇丙酮酸：糖磷酸转移酶活性降低。这是第一份证明TA模块在革兰氏阳性菌中具有生理作用的报告。
