The group I strain of Streptococcus mutans, UA140, produces both the lantibiotic mutacin I and a nonlantibiotic bacteriocin, mutacin IV.
Strains of Streptococcus mutans produce at least three mutacins, I, II, and III. Mutacin II is a member of subgroup AII in the lantibiotic family of bacteriocins, and mutacins I and III belong to subgroup AI in the lantibiotic family. In this report, we characterize two mutacins produced by UA140, a group I strain of S. mutans. One is identical to the lantibiotic mutacin I produced by strain CH43 (F. Qi et al., Appl. Environ. Microbiol. 66:3221-3229, 2000); the other is a nonlantibiotic bacteriocin, which we named mutacin IV. Mutacin IV belongs to the two-peptide, nonlantibiotic family of bacteriocins produced by gram-positive bacteria. Peptide A, encoded by gene nlmA, is 44 amino acids (aa) in size and has a molecular mass of 4,169 Da; peptide B, encoded by nlmB, is 49 aa in size and has a molecular mass of 4,826 Da. Both peptides derive from prepeptides with glycines at positions -2 and -1 relative to the processing site. Production of mutacins I and IV by UA140 appears to be regulated by different mechanisms under different physiological conditions. The significance of producing two mutacins by one strain under different conditions and the implication of this property in terms of the ecology of S. mutans in the oral cavity are discussed.
Qi
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Department of Oral Biology, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA. fqi@mail.dental.uab.edu
Chen
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Caufield
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PW
D000192:Actinomycetales / Q000187:drug effects; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001430:Bacteriocins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003731:Dental Caries / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010455:Peptides; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000382:microbiology; D013291:Streptococcus / Q000187:drug effects; D013295:Streptococcus mutans / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D010455:Peptides; C416548:mutacin I; C425769:mutacin IV