title: Genomic island TnSmu2 of Streptococcus mutans harbors a nonribosomal peptide synthetase-polyketide synthase gene cluster responsible for the biosynthesis of pigments involved in oxygen and H2O2 tolerance.
abstract: The oral biofilm community consists of >800 microbial species, among which Streptococcus mutans is considered a primary pathogen for dental caries. The genomic island TnSmu2 of S. mutans comprises >2% of the genome. In this study, we demonstrate that TnSmu2 harbors a gene cluster encoding nonribosomal peptide synthetases (NRPS), polyketide synthases (PKS), and accessory proteins and regulators involved in nonribosomal peptide (NRP) and polyketide (PK) biosynthesis. Interestingly, the sequences of these genes and their genomic organizations and locations are highly divergent among different S. mutans strains, yet each TnSmu2 region encodes NRPS/PKS and accessory proteins. Mutagenesis of the structural genes and putative regulatory genes in strains UA159, UA140, and MT4653 resulted in colonies that were devoid of their yellow pigmentation (for strains UA140 and MT4653). In addition, these mutant strains also displayed retarded growth under aerobic conditions and in the presence of H(2)O(2). High-performance liquid chromatography profiling of cell surface extracts identified unique peaks that were missing in the mutant strains, and partial characterization of the purified product from UA159 demonstrated that it is indeed a hybrid NRP/PK, as predicted. A genomic survey of 94 clinical S. mutans isolates suggests that the TnSmu2 gene cluster may be more prevalent than previously recognized.
authors.affiliation: College of Dentistry, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Chenggang
authors.initials: C
authors.lastname: Wu
authors.forename: Robert
authors.initials: R
authors.lastname: Cichewicz
authors.forename: Yihong
authors.initials: Y
authors.lastname: Li
authors.forename: Jinman
authors.initials: J
authors.lastname: Liu
authors.forename: Bruce
authors.initials: B
authors.lastname: Roe
authors.forename: Joseph
authors.initials: J
authors.lastname: Ferretti
authors.forename: Justin
authors.initials: J
authors.lastname: Merritt
authors.forename: Fengxia
authors.initials: F
authors.lastname: Qi
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D023061:Gene Order; D044404:Genomic Islands; D006861:Hydrogen Peroxide / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation; D016877:Oxidants / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010453:Peptide Synthases / Q000235:genetics*; D010860:Pigments, Biological / Q000096:biosynthesis / Q000378:metabolism*; D048630:Polyketide Synthases / Q000235:genetics*; D011110:Polymorphism, Genetic; D013295:Streptococcus mutans / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D016877:Oxidants; D010860:Pigments, Biological; D048630:Polyketide Synthases; D006861:Hydrogen Peroxide; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase; D010100:Oxygen