Identification and Characterization of a Putative Manganese Export Protein in Vibrio cholerae

Abstract

ABSTRACT Manganese plays an important role in the cellular physiology and metabolism of bacterial species, including the human pathogen Vibrio cholerae . The intracellular level of manganese ions is controlled through coordinated regulation of the import and export of this element. We have identified a putative manganese exporter (VC0022), named mneA ( m a n ganese e xporter A ), which is highly conserved among Vibrio spp. An mneA mutant exhibited sensitivity to manganese but not to other cations. Under high-manganese conditions, the mneA mutant showed an almost 50-fold increase in intracellular manganese levels and reduced intracellular iron relative to those of its wild-type parent, suggesting that the mutant's manganese sensitivity is due to the accumulation of toxic levels of manganese and reduced iron. Expression of mneA suppressed the manganese-sensitive phenotype of an Escherichia coli strain carrying a mutation in the nonhomologous manganese export gene, mntP , further supporting a manganese export function for V. cholerae MneA. The level of mneA mRNA was induced approximately 2.5-fold after addition of manganese to the medium, indicating regulation of this gene by manganese. This study offers the first insights into understanding manganese homeostasis in this important pathogen. IMPORTANCE Bacterial cells control intracellular metal concentrations by coordinating acquisition in metal-limited environments with export in metal-excess environments. We identified a putative manganese export protein, MneA, in Vibrio cholerae . An mneA mutant was sensitive to manganese, and this effect was specific to manganese. The mneA mutant accumulated high levels of intracellular manganese with a concomitant decrease in intracellular iron levels when grown in manganese-supplemented medium. Expression of mneA in trans suppressed the manganese sensitivity of an E. coli mntP mutant. This study is the first to investigate manganese export in V. cholerae .