Biology ETDs

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This research reports the effects of two metabolic groups of bacteria on physiological activity and cognitive function in C57BL/6 mice. In one experiment, the mice on a diet supplemented with red kidney bean for 24 hr were able to complete an eight-arm radial learning maze in a shorter time than mice on a diet without red kidney beans. The median time required for mice to complete the maze when fed red kidney beans was 118 sec while the median time for mice on standard diet to finish the maze was 270 sec. Based on the cycle threshold values when using universal bacterial primers on mid-small intestine contents, the mice fed the red kidney bean diet had a greater number of gene copies of bacteria as compared to the intestinal contents of mice receiving the standard diet. The introduction of 1 X 109 live cells of Desulfovibrio vulgaris into the stomach of mice by gavage resulted in reducing the rate at which contents in the small intestine traveled and impaired cognitive function as assessed using the eight arm radial learning maze. The impaired performance of mice in the learning maze occurred only with actively metabolizing cells of D. vulgaris and not with heat-killed cells of D. vulgaris, or substituting saline or fermentable sugars for live cells of D. vulgaris. The amount of time spent in the center of the maze for mice receiving live D. vulgaris cells was 34 sec as compared to mice receiving heat-killed cells of D. vulgaris was 15 sec, saline was 13.5 sec and lactulose plus mannitol instead of live cells of D. vulgaris was 15.5 sec. Mice receiving live cells of D. vulgaris had almost ten times as many errors in completion of the maze than mice in the control groups. A contributing factor for impaired maze performance may be the high level of H2S in the mouse intestine.

Project Sponsors

Winkler Bacterial Overgrowth Fund




H2S, intestinal motility, hydrogen sulfide, radial arm maze, bacterial overgrowth, fermentation, working memory, gut, microbiota, microbiome

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Lin, Henry

Second Committee Member

Barton, Larry