CHALON Miriam Carolina
congresos y reuniones científicas
Enterocin CRL35 is active against Gram-negative bacteria regardless of a specific receptor when is anchored in the membrane
CHALÓN, M.C; BARRAZA, D; ACUÑA, L; SESMA, F; MORERO. R.D; MINAHK, C.J; BELLOMIO, A
San Miguel de Tucumán
Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL; 2011
Sociedad Argentina de Microbiología General (SAMIGE)
Enterocin CRL35 is a pediocin-like bacteriocin (subclass IIa) produced by Enterococcus mundtii CRL35. Subclass IIa bacteriocins act on the cell membrane of gram positive bacteria through a pore formation. Apparently, the peptides bind to the cytoplasmic membrane through a very specific receptor, the mannose phosphotransferase system. There are two theories on the mechanism of pore formation: i) they would induce a conformational changes in the receptor to form a channel that remains open or , ii) they would use the receptor simply as an anchor and then form the pore in the membrane. In both cases, the pore formation leads to the leakage of ions, dissipation of proton motive force and release of ATP and essential metabolites. In order to study the mechanism by which enterocin CRL35 induces the loss of membrane integrity, we led the bacteriocin to the cell membrane of E. coli, by fusing it with EtpM, a protein of the type II secretion system from E. coli O157: H7. Previously in our laboratory, we carried out a transcriptional fusion between structural genes of enterocin CRL35 and colicin V thus obtaining the chimera MunA-CvaC active against Gram-positive and Gram- negative bacteria. In this work we constructed the fusions etpM-munA and etpM-munA-cvaC under the tight control of the pBAD promoter (repressed by glucose and induced by arabinose). In addition we carried out the co-expression of EtpM-MunA and EtpM-MunA-CvaC with the enterocin CRL35 and colicin V immunity proteins. This result is surprising because it is shown for the very first time that enterocin CRL35 is capable of acting on Gram-negative bacteria when it is anchored in the plasma membrane, independently of its specific receptor.