Studies On Lysogenic Lactobacillus Fermentum And Its Temperate Bacteriophages

As the major fermented dairy products in China, yogurts can promote human health and be favorite for most consumers. The starter culture of a traditional yogurt normally includes a combination of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. At the present, the traditional Lactobacillus delbrueckii subsp. bulgaricus culture in many yogurt products has been replaced by or combinated with Bifidobacterium and Lb. acidphilus. To improve a yogurt's health value and manufacture various characteristic yogurts from other materials such as amylaceous material and corn and so on, it is necessary to investigate the physiological features of other Lactobacilli. Like the fermentation process of cheese, one of the greatest hazards of the manufacture process of yogurts is bacteriophage infection, which is capable of slowing or even stopping production. In recent years, phage infection of cultures used in yogurt production has become more frequent because of increased plant scale and heavier production schedules in China. To our knowledge, little is known about the lactic acid bacteria bacteriophage from Chinese fermented dairy products. The objective of this study was to isolate and characterize the strains of Lactobacillus and their bacteriophages so as to effective prevent the infection of bacteriophage.20 isolates isolated from 20 various brands of yogurt were further confirmed to be lactobacilli by its rod cell morphology, gram-positive stains, and catalase-negative reaction. Seven strains among the 20 lactobacilli were found to be lysogenic strains by Mitomycin (MMC) induction. And the induced bacteriophages from the lysogenic strains have hexagonal heads, long non-contractile tail, belonging to the Caudovirales order and Siphoviridae family (morphotype B1). They were furthermore confirmed to be the same bacteriophage by identical restriction patterns and were named ΦYB5. Its lysogenic strain was named YB5. SDS-PAGE profile showed that the phage had one major structure protein about 31.9 kDa. Comparing the genomic restriction...