Cao Min, Helmann John D
Department of Microbiology, Cornell University, Ithaca, New York 14853-8101, USA.
J Bacteriol. 2002 Nov;184(22):6123-9. doi: 10.1128/JB.184.22.6123-6129.2002.
Bacitracin resistance is normally conferred by either of two major mechanisms, the BcrABC transporter, which pumps out bacitracin, or BacA, an undecaprenol kinase that provides C(55)-isoprenyl phosphate by de novo synthesis. We demonstrate that the Bacillus subtilis bcrC (ywoA) gene, encoding a putative bacitracin transport permease, is an important bacitracin resistance determinant. A bcrC mutant strain had an eightfold-higher sensitivity to bacitracin. Expression of bcrC initiated from a single promoter site that could be recognized by either of two extracytoplasmic function (ECF) sigma factors, sigma(X) or sigma(M). Bacitracin induced expression of bcrC, and this induction was dependent on sigma(M) but not on sigma(X). Under inducing conditions, expression was primarily dependent on sigma(M). As a consequence, a sigM mutant was fourfold more sensitive to bacitracin, while the sigX mutant was only slightly sensitive. A sigX sigM double mutant was similar to a bcrC mutant in sensitivity. These results support the suggestion that one function of B. subtilis ECF sigma factors is to coordinate antibiotic stress responses.
杆菌肽抗性通常由两种主要机制之一赋予，即BcrABC转运蛋白（它将杆菌肽泵出）或BacA（一种十一异戊二烯醇激酶，通过从头合成提供C(55)-异戊烯基磷酸）。我们证明，编码假定的杆菌肽转运通透酶的枯草芽孢杆菌bcrC（ywoA）基因是一个重要的杆菌肽抗性决定因素。一个bcrC突变株对杆菌肽的敏感性高八倍。bcrC的表达从一个单一启动子位点起始，该位点可被两种胞外功能（ECF）σ因子之一σ(X)或σ(M)识别。杆菌肽诱导bcrC的表达，且这种诱导依赖于σ(M)而不依赖于σ(X)。在诱导条件下，表达主要依赖于σ(M)。因此，一个sigM突变株对杆菌肽的敏感性高四倍，而sigX突变株只是稍有敏感性。一个sigX sigM双突变株在敏感性上与bcrC突变株相似。这些结果支持了枯草芽孢杆菌ECF σ因子的一个功能是协调抗生素应激反应这一观点。
