Intracellular zinc accumulation increases MccJ25 resistance in Escherichia coli

SOCIAS, SERGIO BENJAMIN; VALLEJOS CECILIA; SALOMON, RAÚL A.

San Miguel de Tucumán, Tucumán

Congreso; Congreso de la Sociedad Argentina de Investigacion en Bioquímica y Biología Molecula; 2009

We have observed an intrinsic resistance to the antibiotic MccJ25 in several E. coli strains. In order to identify genes responsible for this phenotype, a genomic library in MudII4042 was constructed from MC4100 Mucts DyojI (pEG109) and used to infect the sensitive strain AB1133. Muductants were selected in the presence of MccJ25. Plasmid DNA was extracted from a MccJ25-resistant clone, digested with HindIII and cloned into pACYC177. This plasmid, named pAC521H, conferred resistance to MccJ25 when transformed into a sensitive strain. The fragment carried by pAC521H was sequenced and located on the 41-min region of the E. coli chromosome. Additional subclones of this plasmid in the vector pACYC184 were constructed. One of them, containing a 4 kb fragment encompassing the genes znuA, znuB and znuC, which encode for the zinc importer ZnuABC, was able to confer resistance to MccJ25. Several experiments showed that ZnuABC neither acts as a MccJ25 pump nor activates one. Interestingly, the individual expression of these genes did not affect the susceptibility to MccJ25, suggesting that the complex ZnuABC is required to confer resistance to the antibiotic. Moreover, the absence of the native zinc exporter, ZntA, leads to an increased resistance to MccJ25. Taken together, the results suggest that the intracellular accumulation of zinc increases the resistance to MccJ25 in E coli.