Zinc Import Mediated by AdcABC is Critical for Colonization of the Dental Biofilm by Streptococcus mutans in an Animal Model

In this study, we sought to identify and characterize the zinc uptake system(s) ofS. mutans, a keystone pathogen in dental caries and a causative agent of bacterial endocarditis. Different than other pathogenic bacteria, including several streptococci, that encode multiple zinc import systems, bioinformatic analysis indicated that theS. mutans core genome encodes a single, highly conserved, zinc importer commonly known as AdcABC. Inactivation of the genes coding for the metal ‐binding AdcA (ΔadcA) or both AdcC ATPase and AdcB permease ( ΔadcCB) severely impaired the ability ofS. mutans to grow under zinc ‐depleted conditions. Intracellular metal quantifications revealed that both mutants accumulated less zinc when grown in the presence of a sub‐inhibitory concentration of a zinc‐specific chelator. Notably, the ΔadcCB strain displayed a severe colonization defect in a rat oral infection model. Both Δadc strains were hypersensitive to high concentrations of manganese, showed reduced peroxide tolerance, and formed less biofilm in sucrose ‐containing media when cultivated in the presence of the lowest amount of zinc that support their growth, but not when zinc was supplied in excess. Collectively, this study identifies AdcABC as the major high affinity zinc importer ofS. mutans and provides preliminary evidence that zinc is a growth ‐limiting factor within the dental biofilm.
Source: Molecular Oral Microbiology - Category: Microbiology Authors: Tags: ORIGINAL ARTICLE Source Type: research