The gastrointestinal (GI) tract is a diverse ecosystem with nearly 100 trillion microbial cells. Many of these microbes provide beneficial functions including nutrient uptake and immune development. Dietary probiotics, including yogurt has received interest over the past several years because of its beneficial effects. The aim of this study was to determine if there were quantifiable changes in microbial community structure and diversity within the human GI tract associated with regular consumption of yogurt.
A commercial yogurt was selected based on high Lactobacillus (5.3 x 108 CFUs/mL) and Bifidobacterium (4.2 x 108 CFUs/mL) counts using selective media. The dietary study was conducted with 5 human test subjects (males and females). Subjects refrained from yogurt consumption for 14 days, at the end of which fecal samples were collected. Subjects then followed a daily consumption of 250 g of yogurt for 42 days. Fecal samples were collected every seven days following DNA extraction and terminal restriction fragment length polymorphisms analyses. Lactobacillus, Lac1 and Lac2, and Bifidobacteria, G-Bifid-F and G-Bifid-R primers were used to amplify 16s rRNA, construct clone libraries and for quantitative PCR.
Nonmetric Multidimensional Scaling (NMDS) ordination of tRFLP taxa showed clustering of all test subjects indicating that individuals had similar community structure over time. Shannon Weiner Diversity index increased from day 0 to day 28 and decreased by day 42. qPCR from test subject B indicated that Lactobacillus genes increased by 1.8 orders of magnitude after 42 days of yogurt consumption. Data from clone libraries are currently being analyzed.