Characterization of a New Virulent Phage (MLC-A) of Lactobacillus paracasei

MARÍA LUJÁN CAPRA; ANDREA DEL LUJÁN QUIBERONI; HANS-W. ACKERMANN; SYLVAIN MOINEAU; JORGE ALBERTO REINHEIMER

JOURNAL OF DAIRY SCIENCE

American Dairy Science Association

Lugar: Savoy; Año: 2006 vol. 89 p. 2414 - 2423

0022-0302

A new virulent bacteriophage (MLC-A) was recentlyisolated in Argentina from a probiotic dairy productcontaining a strain of Lactobacillus paracasei. Observationof the lysate with an electron microscope revealedbacteriophage particles with an icosahedral capsid of57 ± 2 nm; with a collar and a noncontractile tail of 156± 3 nm terminating with a baseplate to which a tailfiber was attached. Therefore, phage MLC-A belongs tothe Siphoviridae family. This phage was able to survivethe pasteurization process and was resistant to alcoholsand sodium hypochlorite (400 mg/kg). Only peraceticacid could inactivate high-titer suspensions of phagesin a short time. The maximum rates of phage adsorptionto its host cells were obtained at 30°C with a pH between5 and 7, and in the presence of calcium or magnesiumions. The host range of phage MLC-A encompassedL. paracasei and Lactobacillus casei strains, butit was not able to infect Lactobacillus rhamnosus orLactobacillus gasseri strains. One-step growth kineticsof its lytic development revealed latent and burst periodsof 30 and 135 min, respectively, with a burst sizeof about 69 ± 4 plaque-forming units per infected cell.Phage MLC-A had a distinctive restriction profile whencompared with the 2 well-studied Lactobacillus phages,PL-1 and J-1. The genome size of the MLC-A phagewas estimated to be approximately 37 kb. This studypresents the description of the first phage specific for L.paracasei isolated in Argentina. The isolation of phageMLC-A indicates that, beside lactic acid bacteria starters,probiotic cultures can also be sensitive to virulentphages in industrial processes.