CONICET | Buscador de Institutos y Recursos Humanos

Twenty-two Lactobacillus paracasei phages were isolated from an industrial plant that manufactures a probiotic dairy product. Basically selected by different restriction profiles, morphology, host range, calcium-dependency and thermal resistance of 8 phages were investigated. High-pressure homogenization was applied on two phages. Many common restriction fragments might evidence certain evolutive relationship among isolates. All belonged to Siphoviridae family (B1 morphotype), were specific for Lb. casei and paracasei strains showing identical host spectrum, and only one was independent of calcium for completing its lytic cycle. Phages showed extraordinary heat resistance, while different responses were found for both tested phages when high-pressure homogenization was applied. All studied phages might derive from a singular phage that originally infected the factory. Then, interacting with the only host strain and trying to survive to the adverse environment, evolved genetically and generated a family of close related phages, which settle down in different industrial plant areas.