Examinando por Autor "Vásquez, CC"

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    The ompW (porin) gene mediates methyl viologen (paraquat) efflux in Salmonella enterica serovar Typhimurium
    (Elsevier, 2007-07-01) Gil, F; Ipinza, F; Fuentes, J; Pumeron, P; Villarreal, JM; Aspée, A; Mora, GC; Vásquez, CC; Saavedra, C
    Porins are channels that enable passive diffusion of hydrophilic solutes, nutrients and toxins through the outer bacterial membrane. This explains in part the ability of Gram-negative microorganisms to grow in several different environments, as well as their drug resistance. OmpD is an outer membrane channel that works with the inner membrane pump YddG to expel methyl viologen (MV) from Salmonella enterica serovar Typhimurium: this occurs independently of SmvA, also involved in MV resistance. On the other hand, Delta tolC strains show increased MV resistance when compared to wild-type cells, suggesting that there may be other porin(s) that could function with SmvA to pump MV out of S. typhimurium. A strong candidate is OmpW. Here we show that Delta ompW strains of S. typhimurium are 2.5-fold more sensitive to MV than the wild-type strain. Transcriptional fusions replacing ompW by lacZ show that ompW is induced at least 2-fold in the presence of MV. This result was observed both at the mRNA and protein levels, suggesting that ompW participates in MV resistance. In addition, Delta smvA Delta ompW strains are not fully complemented by smvA, suggesting that OmpW may function through an independent pathway different from that used by SmvA to move MV outside the cell. (C) 2007 Elsevier Masson SAS. All rights reserved.
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    The product of the qacC gene of Staphylococcus epidermidis CH mediates resistance to β-lactam antibiotics in Gram-positive and Gram-negative bacteria
    (Elsevier, 2005-05-01) Fuentes, DE; Navarro, CA; Tantaleán, JC; Araya, MA; Saavedra, CP; Pérez, JM; Calderón, IL; Youderian, PA; Mora, GC; Vásquez, CC
    We have characterized a natural isolate of Staphylococcus epidermidis resistant to heavy metals that carries a small 2391-bp plasmid, pSepCH, encoding the qacC gene. The S. epidermidis qacC gene confers resistance to a number of beta-lactam antibiotics and to ethidium bromide in its natural host and in Escherichia coli K12 and Salmonella enterica sv. Typhimurium. This is the first communication of a small multidrug resistance (SMR) pump involved in resistance to beta-lactam antibiotics. Experiments using tolC, ompW and ompD mutant strains of S. Typhimurium demonstrated that the beta-lactam antibiotic resistance conferred by this pump does not depend on these outer membrane proteins. (c) 2005 Elsevier SAS. All rights reserved.