A σ54-dependent PTS permease of the mannose family is responsible for sensitivity of Listeria monocytogenes to mesentericin Y105

Sensitivity of Listeria monocytogenes to the bacteriocin mesentericin Y105 was previously shown to be dependent on the σ54 subunit of the RNA polymerase. This points towards expression of particular σ54-dependent genes. The present study describes first, ManR, a new σ54-associated activator, and second, \(EII_{t}^{Man}\) , a new σ54-dependent PTS permease of the mannose family, both involved in sensitivity to mesentericin Y105, since interruption of their corresponding genes led to resistance of L. monocytogenes EGDe. \(EII_{t}^{Man}\) is likely composed of three subunits encoded by the mpt operon (mptA, mptC and mptD genes). Interruption of either the proximal (mptA) or distal (mptD) gene led to resistance, supporting results obtained in Enterococcus faecalis. Accordingly, such PTS permeases of the mannose family should be involved in sensitivity of different target strains to mesentericin Y105. In L. monocytogenes, expression of the mpt operon is shown to be controlled by σ54 and ManR and to be induced by both glucose and mannose. The latter result indicates that these sugars are transported by the \(EII_{t}^{Man}\) permease. Moreover, these sugars correlatively induce sensitivity of L. monocytogenes to mesentericin Y105, strongly favouring the primary role of \(EII_{t}^{Man}\) . MptD, a membrane subunit of \(EII_{t}^{Man}\) , presents an additional domain compared to most IIDMan subunits described in data banks. An in-frame deletion of this domain in mptD led to resistance of L. monocytogenes, showing its connection with sensitivity and suggesting that it could be directly involved in the recognition of the target cell by mesentericin Y105. Taken together, the results of this work demonstrate that \(EII_{t}^{Man}\) is prominent in sensitivity to mesentericin Y105 and could be a receptor for subclass IIa bacteriocins.