The Maltose ABC Transporter in Lactococcus lactis Facilitates High-Level Sensitivity to the Circular Bacteriocin Garvicin ML
The Maltose ABC Transporter in Lactococcus lactis Facilitates High-Level Sensitivity to the Circular Bacteriocin Garvicin ML
复制标题
DOI：
10.1128/aac.00314-12
复制
发表时间：
2012-06-01
影响因子：
4.9
通讯作者：
Diep, Dzung B.
中科院分区：
文献类型：
--
作者：
Gabrielsen, Christina;Brede, Dag A.;Diep, Dzung B.
我们产生并表征了一系列乳酸乳球菌IL 1403的自发突变体，其对环状细菌素Garvicin ML（GarML）的敏感性平均降低6至11倍。碳水化合物发酵测定突出了这些突变体中碳水化合物代谢的变化，特别是代谢淀粉和麦芽糖的能力的丧失。PCR和测序结果表明，在GarML抗性突变体中自发发生了一个13.5-kb的染色体缺失，包含12个开放阅读框，主要涉及淀粉和麦芽糖的利用。生长实验揭示了对GarML的敏感性与碳分解代谢物阻遏（CCR）之间的相关性;即，当野生型细胞在麦芽糖和半乳糖作为唯一的碳水化合物上生长时，对GarML的敏感性显著增加，这种作用通过葡萄糖的存在而减轻。突变体中缺失的基因包括malEFG，它编码CCR调节的膜结合麦芽糖ABC转运蛋白。这三个基因的突变体的互补恢复正常的敏感性细菌素，这表明麦芽糖ABC转运蛋白的抗菌活性的GarML中的重要作用。这一观点得到了以下事实的支持：对GarML的敏感性水平是剂量依赖性的，随着malEFG表达水平的提高而增加，超过50倍。据我们所知，这是第一次一个特定的蛋白质复合物已被证明参与敏感性的环状细菌素。
We generated and characterized a series of spontaneous mutants of Lactococcus lactis IL1403 with average 6- to 11-fold-lowered sensitivities to the circular bacteriocin garvicin ML (GarML). Carbohydrate fermentation assays highlighted changes in carbohydrate metabolism, specifically loss of the ability to metabolize starch and maltose, in these mutants. PCR and sequencing showed that a 13.5-kb chromosomal deletion encompassing 12 open reading frames, mainly involved in starch and maltose utilization, had spontaneously occurred in the GarML-resistant mutants. Growth experiments revealed a correlation between sensitivity to GarML and carbon catabolite repression (CCR); i.e., sensitivity to GarML increased significantly when wild-type cells were grown on maltose and galactose as sole carbohydrates, an effect which was alleviated by the presence of glucose. Among the genes deleted in the mutants were malEFG, which encode a CCR-regulated membrane-bound maltose ABC transporter. The complementation of mutants with these three genes recovered normal sensitivity to the bacteriocin, suggesting an essential role of the maltose ABC transporter in the antimicrobial activity of GarML. This notion was supported by the fact that the level of sensitivity to GarML was dose dependent, increasing with higher expression levels of malEFG over a 50-fold range. To our knowledge, this is the first time a specific protein complex has been demonstrated to be involved in sensitivity to a circular bacteriocin.