title: How bacteria protect themselves against channel-forming colicins.
abstract: Here we review the mechanisms that bacterial cells use to protect themselves against channel-forming colicins. Four mechanisms are examined: immunity, resistance, tolerance and PacB character. Immunity confers protection to colicinogenic cells against the colicin they produce, since the colicinogenic plasmid bears the genetic determinant for such immunity protein. Resistance is provided by modifications on colicin receptors located on the outer membrane. It prevents colicin adsorption and protects against those colicins sharing a common receptor. Tolerance is achieved by changes in the translocation system. The adsorbed colicin is not translocated toward the periplasmic space. This impedes its insertion into the cell membrane as well as the formation of the transmembrane channel. Tolerance confers protection against colicins that share the same translocation system. Finally, we discuss the PacB character, that confers protection against all known channel-forming colicins. The latter property is encoded by non-colicinogenic plasmids in the H-incompatibility complex.
authors.affiliation: Experimental Biology Institute, Faculty of Science, Venezuelan Central University, Caracas. galonso@neblina.reaccium.ve
authors.forename: G
authors.initials: G
authors.lastname: Alonso
authors.forename: G
authors.initials: G
authors.lastname: Vílchez
authors.forename: V
authors.initials: V
authors.lastname: Rodríguez Lemoine
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects*; D003087:Colicins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D011815:R Factors / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology; D013691:Tellurium / Q000494:pharmacology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; C028593:colicin receptor, E coli; D013691:Tellurium