Phage resistant mutants of Lactobacillus delbrueckii may have functional properties that differ from those of parent strains

VINDEROLA, G.; BRIGGILER-MARCÓ, M.; GUGLIELMOTTI, D.; PERDIGÓN, G.; GIRAFFA, G.; REINHEIMER, J.; QUIBERONI, A.

INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY

Elsevier

Año: 2007 vol. 116 p. 96 - 102

0168-1605

Three commercial phage sensitive Lactobacillus delbrueckii strains (identified as Ab1, YSD V and Ib3), and four spontaneous phage-resistantmutants isolated from them were tested for their capacity to activate the gut mucosal immune response in mice, as indicated by the numbers ofIgA-producing cells. Random Amplified Polymorphic DNA (RAPD) analysis revealed a strong genetic homology between the sensitive strainsand their respective derivatives. The phage-resistant mutants exhibited high levels of phage resistance, elevated stability of this phenotype andtechnological properties comparable to those of their respective parent strains. The tolerance to acidic conditions, bile salts and lysozyme wasstrain dependent and total cell viability losses as a result of exposure to all three stresses ranged from 2.0 to 3.7 log units. All the strains werehighly resistant to a simulated gastric solution of pH 3, while significant additional losses in cell viability were observed when acid treated cellswere exposed to bile salts and lysozyme. BALB/c mice received pure cultures of Lb. delbrueckii sensitive and phage-resistant strains for 2, 5 or7 consecutive days. The ability of the parent strains to activate the small intestine immune response was preserved or enhanced in phage-resistantmutants. The maximal proliferation of IgA+ cells was observed at day 5 or 7, depending on the strain. Mutants isolated in this study using naturalselection strategies had improved phage resistance, adequate technological properties and satisfactory gut mucosal immunostimulation ability, andso would be good candidates for industrial applications in functional foods.