[W10-5/ODP-198] Classification and characterization of bacteriocin immunity factors in Streptococcus mutans
Streptococcus mutans is a pathogen associated with dental caries and systemic diseases such as stroke and endocarditis. They produce bacteriocins known as mutacins to compete with other bacteria and possess immune factors for self-protection. Here, we investigated the elements responsible for nisin A (a bacteriocin produced by Lactococcus lactis) resistance in S. mutans and their contribution to mutacins resistance. Based on genome sequences of 124 S. mutans isolates, we classified the nisin A-resistance regions into six types based on the different combinations of 3 immunity factors, mutFEG, nsrX, and mutXYZ, and the presence of mutacin synthesis operon upstream of mutF. Data shows that NsrX effectively acts against nisin A but not mutacins, while the newly identified ABC transporter MutXYZ acts against three mutacins but not nisin A. Three types of MutFEG are classified based on their amino acid sequences, and each type conferred a different resistance ability. Additionally, mutFEG-like structures could be found in various streptococcal species isolated from humans, chimpanzees, monkeys, bears, and hamsters. Our findings suggest that the evolution and mobility of immunity factors may promote bacteriocin resistance among streptococcal species, making the intraspecies and interspecies competition even more complicated and consequently altering the bacterial flora composition.