A streptococcal NRAMP homologue is crucial for the survival ofStreptococcus agalactiaeunder low pH conditions

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Abstract

Summary

Streptococcus agalactiaeor Group BStreptococcus(GBS) is a commensal bacterium of the human gastrointestinal and urogenital tracts as well as a leading cause of neonatal sepsis, pneumonia and meningitis. Maternal vaginal carriage is the main source for GBS transmission and thus the most important risk factor for neonatal disease. Several studies in eukaryotes identified a group of proteins natural resistance-associated macrophage protein (NRAMP) that function as divalent cation transporters for Fe2+ and Mn2+ and confer on macrophages the ability to control replication of bacterial pathogens. Genome sequencing predicted potential NRAMP homologues in several prokaryotes. Here we describe for the first time, a pH-regulated NRAMP Mn2+/Fe2+ transporter in GBS, designated MntH, which confers resistance to reactive oxygen species (ROS) and is crucial for bacterial growth and survival under low pH conditions. Our investigation implicates MntH as an important colonization determinant for GBS in the maternal vagina as it helps bacteria to adapt to the harsh acidic environment, facilitates bacterial adherence, contributes to the coexistence with the vaginal microbiota and plays a role in GBS intracellular survival inside macrophages.

Group B Streptococci are human commensals capable of causing neonatal sepsis, pneumonia and meningitis. Maternal vaginal carriage is the most important risk factor for neonatal disease. In eukaryotes, the Natural Resistance-Associated Macrophage Protein (NRAMP) functions as a divalent cation transporters for Fe2+ and Mn2+ and confers on macrophages the ability to control replication of bacterial pathogens. Here we describe for first time, a pH-regulated NRAMP transporter in GBS, designated MntH, as an important colonization determinant for GBS as it helps bacteria to adapt the harsh acidic environments, facilitates bacterial adherence, contributes to the coexistence with the vaginal microbiota and plays a role in GBS survival inside macrophages.

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