title: Characterization of a new virulent phage (MLC-A) of Lactobacillus paracasei.
abstract: A new virulent bacteriophage (MLC-A) was recently isolated in Argentina from a probiotic dairy product containing a strain of Lactobacillus paracasei. Observation of the lysate with an electron microscope revealed bacteriophage particles with an icosahedral capsid of 57 +/- 2 nm; with a collar and a noncontractile tail of 156 +/- 3 nm terminating with a baseplate to which a tail fiber was attached. Therefore, phage MLC-A belongs to the Siphoviridae family. This phage was able to survive the pasteurization process and was resistant to alcohols and sodium hypochlorite (400 mg/kg). Only peracetic acid could inactivate high-titer suspensions of phages in a short time. The maximum rates of phage adsorption to its host cells were obtained at 30 degrees C with a pH between 5 and 7, and in the presence of calcium or magnesium ions. The host range of phage MLC-A encompassed L. paracasei and Lactobacillus casei strains, but it was not able to infect Lactobacillus rhamnosus or Lactobacillus gasseri strains. One-step growth kinetics of its lytic development revealed latent and burst periods of 30 and 135 min, respectively, with a burst size of about 69 +/- 4 plaque-forming units per infected cell. Phage MLC-A had a distinctive restriction profile when compared with the 2 well-studied Lactobacillus phages, PL-1 and J-1. The genome size of the MLC-A phage was estimated to be approximately 37 kb. This study presents the description of the first phage specific for L. paracasei isolated in Argentina. The isolation of phage MLC-A indicates that, beside lactic acid bacteria starters, probiotic cultures can also be sensitive to virulent phages in industrial processes.
authors.affiliation: Instituto de Lactología Industrial (INLAIN), Facultad de Ingeniería Química (Universidad Nacional del Litoral), Santiago del Estero 2829, 3000 Santa Fe, Argentina. mcapra@fbcb.unl.edu.ar
authors.forename: M L
authors.initials: ML
authors.lastname: Capra
authors.forename: A
authors.initials: A
authors.lastname: Del L Quiberoni
authors.forename: H-W
authors.initials: HW
authors.lastname: Ackermann
authors.forename: S
authors.initials: S
authors.lastname: Moineau
authors.forename: J A
authors.initials: JA
authors.lastname: Reinheimer
mesh_terms: D000327:Adsorption; D000438:Alcohols / Q000494:pharmacology; D001118:Argentina; D001435:Bacteriophages / Q000254:growth & development / Q000302:isolation & purification* / Q000648:ultrastructure; D002413:Cations, Divalent / Q000494:pharmacology; D004279:DNA, Viral / Q000032:analysis; D003611:Dairy Products / Q000382:microbiology / Q000821:virology; D005285:Fermentation; D005511:Food Handling / Q000379:methods; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000821:virology*; D008854:Microscopy, Electron; D010463:Peracetic Acid / Q000494:pharmacology; D019936:Probiotics; D017906:Siphoviridae / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D012973:Sodium Hypochlorite / Q000494:pharmacology; D010948:Viral Plaque Assay
chemical_list: D000438:Alcohols; D002413:Cations, Divalent; D004279:DNA, Viral; D012973:Sodium Hypochlorite; D010463:Peracetic Acid