Date Approved


Degree Type

Open Access Senior Honors Thesis

Department or School


First Advisor

Daniel L. Clemans

Second Advisor

Kristin E. Judd

Third Advisor

Marianne Laporte


Lactobacillus rhamnosus GG (LGG) is one of the best studied probiotic organisms. The ability of probiotics to adhere to other microorganisms and the intestinal epithelium is thought to play a major role in their protective functions. Coaggregation is an important mechanism for biofilm formation by microorganisms. The goals of this study were to examine the ways in which nutrient variation affects intercellular interactions between LGG and other gut microbes and the hydrophobic character of LGG. We hypothesized that nutritional variation may affect the ability of LGG to coaggregate and form biofilms and thus affect its probiotic characteristics and ability to colonize the gastrointestinal tract. Lactobacillus rhamnosus GG was cultured anaerobically in different formulations of tryptone, yeast extract, and glucose (TYG) medium in order to simulate a milk-based, plant-based, and meat-based diet. Since the gut is mainly colonized by microorganisms belonging to the Firmicutes and Bacteroidetes phyla, we tested the coaggregation ability between LGG and Bacteroides spp. and Parabacteroides spp. Our results suggest that coaggregation varies by media type, with LGG cultured in BeYG [Beef extract (meat protein), yeast extract, and glucose] medium exhibiting the highest coaggregation scores. Hydrophobicity values of LGG cells cultured in varying nutrient conditions differed significantly by media type, and LGG cultured in BeYG exhibited the highest hydrophobicity scores. These results indicate that different nutrient conditions may enhance the ability of LGG to colonize the human gut microbiome and enhance its ability to act as a successful probiotic.

Included in

Biology Commons