Role of the high-affinity zinc uptake znuABC system in Salmonella enterica serovar typhimurium virulence

Abstract

The Salmonella enterica serovar Typhimurium znuABC genes encoding a high-affinity zinc uptake system and its regulatory zur gene have been cloned. Salmonella serovar Typhimurium zur and znuC knockout mutants have been constructed by marker exchange. The 50% lethal dose of the znuC mutant increased when either orally or intraperitoneally inoculated in BALB/c mice, while virulence of the zur mutant decreased only when mice were intraperitoneally challenged.

FIG. 1.

Chromosomal DNAs from Salmonella serovar Typhimurium ATCC 14028 wild-type strain (lanes 2 and 4) and the zur (lane 1) and znuC (lane 3) mutants were subjected to PCR analysis with primer pairs ZurA-ZurB (lanes 1 and 2) and ZnuC1-ZnuC2 (lanes 3 and 4). Kilobase pairs are indicated on the left.

FIG. 2.

Expression of zur and znuC genes in wild-type (wt), Zur⁻, and ZnuC⁻ strains of Salmonella serovar Typhimurium determined as β-galactosidase activity through either zur-lacZ or znuC-lacZ fusions. Transcription of the znuC gene in wild-type cells in the presence of EDTA with or without ZnSO₄ (Zn) is also shown. Concentrations of EDTA and ZnSO₄ used were 1.5 and 1 mM, respectively. β-Galactosidase was measured in mid-logarithmic phase cultures growing in LB medium as described previously (6). Data presented are the averages of three independent experiments with duplicate samples.