Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
J Dairy Sci. 2013 Aug;96(8):4928-37. doi: 10.3168/jds.2013-6688. Epub 2013 Jun 5.
The microbial composition of raw and pasteurized milk is assessed on a daily basis. However, many such tests are culture-dependent, and, thus, bacteria that are present at subdominant levels, or that cannot be easily grown in the laboratory, may be overlooked. To address this potential bias, we have used several culture-independent techniques, including flow cytometry, real-time quantitative PCR, and high-throughput DNA sequencing, to assess the microbial population of milk from a selection of commercial milk producers, pre- and postpasteurization. The combination of techniques employed reveals the presence of a previously unrecognized and diverse bacterial population in unpasteurized cow milk. Most notably, the use of high-throughput DNA sequencing resulted in several bacterial genera being identified in milk samples for the first time. These included Bacteroides, Faecalibacterium, Prevotella, and Catenibacterium. Our culture-independent analyses also indicate that the bacterial population of pasteurized milk is more diverse than previously appreciated, and that nonthermoduric bacteria within these populations are likely to be in a damaged, nonculturable form. It is thus apparent that the application of state-of-the-art approaches can provide a detailed insight into the bacterial composition of milk and could potentially be employed in the future to investigate the factors that influence the composition of these populations.
我们每天都会对生奶和巴氏杀菌奶的微生物组成进行评估。然而，许多此类测试都是基于培养的，因此，可能会忽略那些处于次要水平或难以在实验室中生长的细菌。为了解决这个潜在的偏差，我们使用了多种非培养依赖性技术，包括流式细胞术、实时定量 PCR 和高通量 DNA 测序，以评估来自一些商业牛奶生产商的生奶和巴氏杀菌奶的微生物种群。所采用的技术组合揭示了未经巴氏杀菌的牛奶中存在以前未被识别的多样细菌种群。值得注意的是，高通量 DNA 测序的使用首次在牛奶样本中鉴定出了几个细菌属。其中包括拟杆菌属、粪杆菌属、普雷沃氏菌属和卡特尼氏菌属。我们的非培养分析还表明，巴氏杀菌奶的细菌种群比以前认为的更加多样化，并且这些种群中的非耐热细菌可能处于受损的、不可培养的状态。因此，很明显，应用最先进的方法可以深入了解牛奶的细菌组成，并有可能在未来用于研究影响这些种群组成的因素。
