9.A.38 The Bacteriocin Immunity Protein (BIP) Family
Bacteria utilize quorum-sensing systems to modulate environmental stress responses. The quorum-sensing system of Streptococcus mutans is mediated by the competence-stimulating peptide (CSP), whose precursor is encoded by the comC gene. A comC mutant of strain GS5 exhibited enhanced antimicrobial sensitivity to a wide variety of different agents. Since the addition of exogenous CSP does not complement this phenotype, the increased tetracycline, penicillin, and triclosan sensitivities must have resulted from repression of the putative bacteriocin immunity protein gene, bip, which is located immediately upstream of comC (Matsumoto-Nakano and Kuramitsu, 2006). Inactivation of bip or smbG (TC# 3.A.1.111.4), another bacteriocin immunity protein gene present within the smb operon in S. mutans GS5, affected sensitivity to a variety of antimicrobial agents. Furthermore, both the bip and smbG genes were upregulated in the presence of low concentrations of antibiotics and were induced during biofilm formation relative to planktonic cells. These results suggest that the antimicrobial sensitivities of a bacterium can be modulated by bacteriocin immunity proteins.
The transport reaction believed to be catalyzed by Bip is:
bacteriocins and antibiotics (in) → bacteriocin and antibiotics (out)