title: Fatty-acid profiles and expression of the fabM gene in a fluoride-resistant strain of Streptococcus mutans.
abstract: OBJECTIVE
  The aim of this study was to compare the membrane fatty acid profile and expression of the fabM gene in a fluoride-resistant Streptococcus mutans strain with those of its wild-type counterpart. Additionally, we aimed to investigate whether mutations were present in the fabM gene of the fluoride-resistant strain.
  
  
  METHODS
  A fluoride-resistant strain of S. mutans was obtained by step-by-step induction in vitro. The fluoride-resistant strain and its wild-type counterpart were grown anaerobically in a brain heart infusion broth, harvested and resuspended in a salt solution for an acid survival assay and a pH-drop experiment. The membrane fatty acid profile was determined by gas chromatography-mass spectrometry. Expression of the fabM gene was quantified by real-time PCR. The fabM gene was also sequenced.
  
  
  RESULTS
  The ability of the fluoride-resistant strain to resist acid stress was greater than that of the wild-type strain. A significant difference in the amount of long-chain monounsaturated fatty acids between the fluoride-resistant strain and the wild-type strain was detected in acidic condition (P<0.01). In addition, the level of fabM mRNA in the fluoride-resistant strain was significantly higher than that of the wild-type strain in the acidic condition as well (P<0.01). However, the sequence of the fabM gene from the fluoride-resistant strain was 100% homologous with that from the wild-type strain.
  
  
  CONCLUSIONS
  The membrane fatty acid profile and expression of the fabM gene in the fluoride-resistant strain were altered compared to the wild-type strain in acidic conditions, but no differences were found in the sequence of the fabM gene.
authors: Department of Endodontics and Operative Dentistry, Ninth People's Hospital, Shanghai Key Laboratory of Stomatology, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Shanghai, China.
authors: Laikuan
authors: L
authors: Zhu
authors: Zhimin
authors: Z
authors: Zhang
authors: Jingping
authors: J
authors: Liang
mesh_terms: D000704:Analysis of Variance; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D003731:Dental Caries / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism*; D005459:Fluorides / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009154:Mutation; D060888:Real-Time Polymerase Chain Reaction; D013295:Streptococcus mutans / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005229:Fatty Acids, Monounsaturated; D005459:Fluorides