Date of Award

Spring 2009

Document Type

Restricted Thesis

Terms of Use

© 2009 Tristan Bice. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts



First Advisor

Amy Cheng Vollmer

Second Advisor

Sara Hiebert Burch


Gut bacteria play essential roles in host organisms to complete digestion, protect against pathogens; and assist in normal development and functioning of the digestive tract and immune system. Gut bacterial profiles are partially genetically determined but change in response to variations in diet. Host-gut-microbial interactions are poorly understood presently, but gut bacteria have been implicated in host energy balance and are involved in fatty acid (FA) metabolism and consequently the host's response to dietary changes. Fecal pellets were collected during a past study on FA dietary preference in mice. In this past study mice were first acclimated to a high fat (10% fat) diet during a baseline period and then were shown to consume significantly different increased of polyunsaturated fatty acids in response to cold (4°C) versus warm (25°C) environments during an experimental period. To investigate whether gut bacterial profiles were shifting in response to the observed dietary change, bacterial 16 DNA was extracted from mouse fecal pellets before and after the baseline period and after the experimental period. Extracted DNA was amplified through PCR using conserved primers for the eubacterial 16S rRNA gene. Amplified sequences were cloned, sequenced, and classified to compare profiles shifts in response to the dietary difference. The two most prevalent phyla of bacteria present in the mouse colon, Bacteroidetes and Firmicutes, did not change significantly over the course of the experiment or with respect to treatment during the experimental phase. Analysis at the familial level revealed a significant increase of Lachnospiraceae species in control mice following the experimental period. No other families showed significant differences across the experimental period. Lachnospiraceae species have been implicated in metabolism of unsaturated fatty acids and may play an important role in dietary-fatty-acid-dependent host energy balance.