Akademik Veri Yönetim Sistemi
APPLIED AND ENVIRONMENTAL MICROBIOLOGY, cilt.62, sa.6, ss.2111-2116, 1996 (SCI-Expanded)
Yogurt and acidophilus milk that contain Lactobacillus acidophilus could promote human health because L. acidophilus can inhibit enteric and food-borne microbial pathogens. To evaluate the stability of dairy L. acidophilus cultures, we studied whether some dairy lactobacilli could be inhibited by phages or bacteriocins released by other dairy lactobacilli, From 20 yogurts and two acidophilus milks purchased at local food markets, 38 Lactobacillus strains were isolated, Eight Lactobacillus type strains were used as controls. With mitomycin induction and agar spot assay, phages and bacteriocins were isolated from these strains and their activities were analyzed, Lactobacillus strains from 11 yogurts released phages, while the strains from most of the remaining products released bacteriocins, One phage, designated phi y8, was characterized, It was spontaneously released from its host strain, L. acidophilus Y8, at a rate of about 10(4)/ml, This phage lysed nine other daily Lactobacillus strains tested, It had a burst size of 100, an elongated prolate head of 39 by 130 nm, a long, flexible but noncontractile tail of 300 nm, and a 54.3-kb linear double-stranded DNA. DNA fingerprinting analysis indicated that L. acidophilus phages of nine yogurts in this study belonged to the same type as phi y8, Although they may be sensitive to bacteriocins, all lysogens resisted further phage attacks, whereas most nonlysogens were sensitive to both phages and bacteriocins, Therefore, Lactobacillus cultures of some American yogurts and acidophilus milks may be unstable or unsafe because they can either he inhibited by phages or bacteriocins or release them to inhibit lactobacilli of other dairy products.