Mechanisms of Resistance to Bacteriocins Targeting the Mannose Phosphotransferase System
Mechanisms of Resistance to Bacteriocins Targeting the Mannose Phosphotransferase System
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DOI：
10.1128/aem.02602-10
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发表时间：
2011-05-01
影响因子：
4.4
通讯作者：
Diep, Dzung B.
中科院分区：
文献类型：
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作者：
Kjos, Morten;Nes, Ingolf F.;Diep, Dzung B.
甘露糖磷酸转移酶系统(Man-PTS)的膜蛋白IIC和IID共同形成一个膜定位的复合体，作为几种不同细菌素的受体，包括小儿茶素样IIa细菌素和IIc类细菌素乳球菌素A。对IIa类细菌素敏感的细菌在细菌素暴露后很容易产生耐药突变。因此，在本研究中，我们研究了乳酸乳球菌的乳霉素A抗性突变株以及对IIa类细菌素具有不同敏感性的自然食品分离株单核细胞增生性李斯特菌。我们发现了两种主要的抗药性机制。第一个涉及下调Man-PTS基因的表达，这既发生在自发耐药突变中，也发生在自然耐药菌株中。第二个涉及Man-PTS系统的正常表达，但这些细胞的潜在耐药机制尚不清楚。在某些情况下，抗性表型与代谢的变化有关，即由于Man-PTS表达的减少而减少了对葡萄糖的生长，同时伴随着对另一种糖(如半乳糖)的促进生长。对这些发现在代谢异质性方面的意义进行了讨论。
The membrane proteins IIC and IID of the mannose phosphotransferase system (Man-PTS) together form a membrane-located complex that serves as a receptor for several different bacteriocins, including the pediocin-like class IIa bacteriocins and the class IIc bacteriocin lactococcin A. Bacterial strains sensitive to class IIa bacteriocins readily give rise to resistant mutants upon bacteriocin exposure. In the present study, we have therefore investigated lactococcin A-resistant mutants of Lactococcus lactis as well as natural food isolates of Listeria monocytogenes with different susceptibilities to class IIa bacteriocins. We found two major mechanisms of resistance. The first involves downregulation of Man-PTS gene expression, which takes place both in spontaneous resistant mutants and in natural resistant isolates. The second involves normal expression of the Man-PTS system, but the underlying mechanism of resistance for these cells is unknown. In some cases, the resistant phenotype was linked to a shift in the metabolism; i.e., reduced growth on glucose due to reduction in Man-PTS expression was accompanied by enhanced growth on another sugar, such as galactose. The implications of these findings in terms of metabolic heterogeneity are discussed.