Instituto de Lactología Industrial (Universidad Nacional del Litoral - CONICET), Santiago del Estero 2829, S3000AOM Santa Fe, Argentina.
Int J Food Microbiol. 2011 Jan 5;144(3):503-10. doi: 10.1016/j.ijfoodmicro.2010.11.009. Epub 2010 Nov 13.
Prophages account for most of the genetic diversity among strains of a given bacterial species, and represent a latent source for the generation of virulent phages. In this work, a set of 30 commercial, collection and dairy-isolated Lactobacillus casei group strains were used. A species-specific PCR assay allowed a reclassification, mainly of strains previously considered Lactobacillus casei, into either Lactobacillus paracasei or Lactobacillus rhamnosus. All the strains were induced with mitomycin C, allowing direct recovering of phage DNA in 25 cases, which corroborates the widely occurrence of lysogeny on Lactobacillus genomes, including probiotic strains of Lactobacillus casei group. Ten out of 11 commercial strains studied contained prophages, evidencing the potential risks of their use at industrial scale. Strains were also induced by treatment with different concentrations of hydrogen peroxide but, however, this agent was not able to evidence a prophage release for any of the strains tested. According to a RAPD-PCR fingerprinting with M13, 1254 and G1 primers, most of the commercial strains presented a high degree of homology and, regarding BglII- and BamHI-restriction profiles of phage DNA, six of them harboured the same prophage. Surprisingly, both Lactobacillus paracasei ATCC 27092 and Lactobacillus paracasei ATCC 27139 shared a second prophage with both an INLAIN collection and a commercial Lactobacillus paracasei strains, whereas two collection strains shared a third one. On the other hand, mitomycin C-inducible prophages were detected only on about a half of the strains isolated from dairy products, which had (with only one exception) from moderate to high correlation coefficients according to RAPD-PCR fingerprinting. After induction, supernatants were filtered and tested against nine Lactobacillus strains of the set sensitive to previously assayed virulent phages, allowing isolation of two new virulent phages: ф iLp1308 and ф iLp84. Both phages were able to lyse all but one strains sensitive to previously assayed phage MLC-A.
原噬菌体在给定细菌物种的菌株中占大多数遗传多样性，并代表了产生毒性噬菌体的潜在来源。在这项工作中，使用了一组 30 种商业、收集和乳制品分离的乳杆菌属乳杆菌组菌株。种特异性 PCR 检测允许重新分类，主要是将先前被认为是乳杆菌乳杆菌的菌株分类为副干酪乳杆菌或鼠李糖乳杆菌。所有菌株均用丝裂霉素 C 诱导，在 25 种情况下可直接回收噬菌体 DNA，这证实了溶原性在乳杆菌基因组中广泛存在，包括乳杆菌属乳杆菌组的益生菌株。在所研究的 11 种商业菌株中有 10 种含有原噬菌体，这表明其在工业规模上使用的潜在风险。用不同浓度的过氧化氢处理也诱导了菌株，但该试剂未能证明任何测试菌株的噬菌体释放。根据 M13、1254 和 G1 引物的 RAPD-PCR 指纹分析，大多数商业菌株具有高度的同源性，并且关于噬菌体 DNA 的 BglII 和 BamHI 限制图谱，其中 6 种含有相同的原噬菌体。令人惊讶的是，副干酪乳杆菌 ATCC 27092 和副干酪乳杆菌 ATCC 27139 与 INLAIN 集合和商业副干酪乳杆菌菌株共享第二个原噬菌体，而两个集合菌株共享第三个原噬菌体。另一方面，仅从乳制品中分离出的菌株中约有一半检测到丝裂霉素 C 诱导的原噬菌体，根据 RAPD-PCR 指纹分析，这些菌株具有从中等到高度相关系数。诱导后，将上清液过滤并针对该组中对先前检测到的毒性噬菌体敏感的 9 种乳杆菌菌株进行测试，允许分离出两种新的毒性噬菌体：ф iLp1308 和 ф iLp84。两种噬菌体都能够裂解除对先前检测到的噬菌体 MLC-A 敏感的菌株之外的所有菌株。
