Zago M, Suarez V, Reinheimer J A, Carminati D, Giraffa G
CRA - Istituto Sperimentale Lattiero Caseario, Lodi, Italy.
J Appl Microbiol. 2007 Feb;102(2):344-51. doi: 10.1111/j.1365-2672.2006.03101.x.
To determine the presence, diffusion and variability of the integrase (int) gene in Lactobacillus delbrueckii ssp. lactis isolated from natural whey starters used for the production of Italian hard cheeses.
A PCR-based protocol aimed to amplify an internal fragment of the int gene was optimized taking into account phage genome sequences available from public databases. Thirty-seven of the 39 strains tested showed the presence of the putative int gene. Southern blot hybridization experiments confirmed data obtained by PCR. The presence of the putative int gene was observed also in 20 of 23 Lact. delbrueckii ssp. lactis lytic phages isolated from the same starter cultures used to isolate strains. Phylogenetic analysis of partial int gene revealed a high similarity both within and between strain- and phage-derived sequences. Sixty per cent of the int-positive strains resulted inducible with mitomycin C, and two of them released active phage particles.
Our preliminary findings seem to suggest that an important number of Lact. delbrueckii ssp. lactis strains associated with the whey starters are lysogenic.
Further contribution to obtain a clearer picture of the complex relationship between thermophilic lactic acid bacteria phage and host in whey starters for Italian, hard-cooked cheeses.
确定从用于生产意大利硬奶酪的天然乳清发酵剂中分离出的德氏乳杆菌乳酸亚种中整合酶(int)基因的存在、扩散和变异性。
考虑到从公共数据库中获取的噬菌体基因组序列,优化了一种基于PCR的方案,旨在扩增int基因的内部片段。在测试的39株菌株中,有37株显示存在推定的int基因。Southern印迹杂交实验证实了PCR获得的数据。在从用于分离菌株的相同发酵剂培养物中分离出的23株德氏乳杆菌乳酸亚种裂解性噬菌体中,也观察到了推定的int基因的存在。对部分int基因的系统发育分析显示,菌株来源和噬菌体来源的序列在内部以及之间都具有高度相似性。60%的int阳性菌株对丝裂霉素C有诱导性,其中两株释放出活性噬菌体颗粒。
我们的初步研究结果似乎表明,与乳清发酵剂相关的大量德氏乳杆菌乳酸亚种菌株是溶源性的。
进一步有助于更清楚地了解用于意大利硬煮奶酪的乳清发酵剂中嗜热乳酸菌噬菌体与宿主之间的复杂关系。