ena-STUDY-TEAGASC-09-01-2015-14:08:37:721-140
The microbial content of raw and pasteurised cow’s milk as determined by molecular approaches including sequencing
The microbial composition of raw and pasteurised milk is assessed by industry on a daily basis. However, many such tests are culture-dependent and thus bacteria that are present at sub-dominant levels and/or that cannot be easily grown in the laboratory may be overlooked. To address this potential bias, we have employed a number of culture-independent techniques, including flow cytometry, real-time qPCR and high throughput sequencing, to assess the microbial population of milk from a selection of commercial milk producers, pre- and post-pasteurisation. The combination of techniques employed reveals the presence of a previously unrecognised and diverse bacterial population in unpasteurised cow’s milk. Most notably, the use of high throughput sequencing resulted in a number of 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 pasteurised milk is more diverse than previously appreciated but that non-thermoduric bacteria within these populations are likely to be in a damaged, non-culturable 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.
The microbial composition of raw and pasteurised milk is assessed by industry on a daily basis. However, many such tests are culture-dependent and thus bacteria that are present at sub-dominant levels and/or that cannot be easily grown in the laboratory may be overlooked. To address this potential bias, we have employed a number of culture-independent techniques, including flow cytometry, real-time qPCR and high throughput sequencing, to assess the microbial population of milk from a selection of commercial milk producers, pre- and post-pasteurisation. The combination of techniques employed reveals the presence of a previously unrecognised and diverse bacterial population in unpasteurised cow’s milk. Most notably, the use of high throughput sequencing resulted in a number of 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 pasteurised milk is more diverse than previously appreciated but that non-thermoduric bacteria within these populations are likely to be in a damaged, non-culturable 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.