Honors Theses

Date of Award

2016

Document Type

Undergraduate Thesis

Department

Biology

First Advisor

Colin Jackson

Relational Format

Dissertation/Thesis

Abstract

A diverse bacterial community makes up the human gut microbiome and is essential not only to digestion, but also to other physiological processes. This bacterial community is subject to change due to external factors including, but not limited to, age, diet, and lifestyle. This study observed the effects of oral probiotic supplements on this bacterial community. Fecal samples were collected from a single subject once each week during alternating two- to six-week cycles of taking and abstaining from the probiotic supplement. The samples were purified, the bacterial cells within lysed, and the enclosed DNA was collected. A portion of the 16S rRNA gene was amplified and sequenced. Sequences were identified and compared to determine whether there were measurable effects of taking the probiotic on the subject's gut microbial community. Firmicutes and Bacteroidetes were the dominant bacterial Phyla, with smaller proportions of Proteobacteria and Actinobacteria. Fluctuations in the subject's gut microbiome were seen at the phylum level and at multiple taxonomic levels within these phyla from the start to the end of the study, but did not generally correspond to cycles of taking the probiotic. Furthermore, the relative abundance of Bacillus coagulans, the bacterial species within the probiotic supplement, did not change dramatically. This study showed that taking this particular probiotic supplement did not cause substantial changes in the relative abundances of bacterial taxonomic groups in the human gut, and that the fluctuations seen were likely due to other factors — for example, normal and expected variations in the individual's gut bacteria, intestinal permeability caused by the subject's food allergies, or other external influences.

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