title: Further characterization of a bacteriocin produced by Lactobacillus paracasei HL32.
abstract: OBJECTIVE
  Purification, identification and partial characterization of bacteriocin produced by Lactobacillus paracasei HL32. It has been shown to have activity against Porphyromonas sp.
  
  
  RESULTS
  The purification of bacteriocin consisting of gel exclusion followed by anion exchange chromatography produced a single band upon an electrophoresis gel with a molecular weight corresponding to 56 kDa. The isolated protein contained 171 amino acids and the first 151 were sequenced. The bacteriocin contained a high percentage of cationic amino acids near the N-terminus, hydrophobic amino acids in the central region (Leu, Ile, Val, Phe, Trp and Gly) and hydrophilic residues (Ser, Asn and Gln) at the C-terminus. This structure did not match with that of previously reported bacteriocins. The antimicrobial activity of the bacteriocin was determined against some pathogens and normal microbiota (P. gingivalis, P. intermedia, T. forsythensis, S. salivarius and S. sanguinis) found in saliva and crevicular fluid. The bacteriocin was found to inhibit P. gingivalis at the minimum bactericidal concentration (MBC) of 0.14 mmol l(-1), but was found not to inhibit the other oral micro-organisms. The bacteriocin was found from transmission electron microscopy studies to cause pore formation in the cytoplasmic membranes of P. gingivalis at the pole and induce potassium efflux. Bacteriocin concentrations of two to four times of MBC were shown to induce haemolysis. The bacteriocin was heat-stable, surviving at 110 degrees C under pressure and possessed activity over a pH range of 6.8-8.5. Only a small reduction of activity was found to occur after incubation in biological fluids (saliva and crevicular fluid).
  
  
  CONCLUSIONS
  A novel bacteriocin has been identified that has selective activity against Porphyromonas sp. associated with periodontal disease.
  
  
  CONCLUSIONS
  The findings of this work gained the knowledge of specific antibacterial activity of bacteriocin against Porphyromonas gingivalis.
authors.affiliation: Department of Stomatology, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla, Thailand.
authors.forename: K
authors.initials: K
authors.lastname: Pangsomboon
authors.forename: S
authors.initials: S
authors.lastname: Bansal
authors.forename: G P
authors.initials: GP
authors.lastname: Martin
authors.forename: P
authors.initials: P
authors.lastname: Suntinanalert
authors.forename: S
authors.initials: S
authors.lastname: Kaewnopparat
authors.forename: T
authors.initials: T
authors.lastname: Srichana
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000627:therapeutic use*; D001430:Bacteriocins / Q000302:isolation & purification / Q000627:therapeutic use*; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000187:drug effects; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000378:metabolism*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010518:Periodontitis / Q000188:drug therapy*; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000648:ultrastructure; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins