title: [Development of pulsed field gel electrophoresis and application for characterization and identification of Lactobacillus and Streptococcus thermophilus].
abstract: OBJECTIVE
  To develop a pulsed field gel electrophoresis (PFGE) method for molecular typing of Lactobacillus and Streptococcus thermophilus (S. thermophilus) and to apply it in identification and characterization of both bacteria isolated from yoghurt collected from Beijing supermarket.
  
  
  METHODS
  The five most useful restriction enzymes including Apa I, Not I, Sfi I, Xba I and Sma I were chosen to cut DNA of 52 strains of Lactobacillus, S. thermophilus as well as associated standard bacteria strains. The endonucleases and electrophoresis conditions for PFGE analysis were optimized and applied in molecular typing of Lactobacillus and S.thermophilus isolates. Cluster analysis based on the PFGE data was conducted. The identification results of PFGE were compared with those obtained in biochemical and 16s ribosomal RNA PCR identification tests.
  
  
  RESULTS
  Not I was suitable for L. bulgaricus, L. fermentum and L. delbrueckii digestion. While Apa I was an appropriate endonuclease for S. thermophilus, L. acidophilus and L. casei digestion. The results of molecular typing indicated that 24 strains of L.bulgaricus and 15 strains of S. thermophilus were grouped into 8 types by PFGE method, respectively. While 7 strains of L.acidophilus were grouped into 3 types and 2 strains of L. delbrueckii were grouped into 2 different PFGE types.
  
  
  CONCLUSIONS
  The results of PFGE analysis are in compliance with those of 16s rRNA PCR and biochemical identification. The PFGE method developed in this study is suitable for molecular characterization of both Lactobacillus and S. thermophilus.
authors.affiliation: Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
authors.forename: Yin-ping
authors.initials: YP
authors.lastname: Dong
authors.forename: Sheng-hui
authors.initials: SH
authors.lastname: Cui
authors.forename: Hong-xia
authors.initials: HX
authors.lastname: Yu
authors.forename: Feng-qin
authors.initials: FQ
authors.lastname: Li
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods*; D007778:Lactobacillus / Q000145:classification / Q000302:isolation & purification*; D048249:Streptococcus thermophilus / Q000145:classification / Q000302:isolation & purification*