Acid and base, as measured by pH, are important to promote and/or control bacterial growth and survival in all environments, from soil and water to the human skin and intestine. Microbes form acids during food production, and acids are important food preservatives. Acid and base influence microbial production of biofuels and pharmaceuticals. Acid and base production change the external environment of growing bacteria but mechanisms of transport and metabolism help bacterial cells maintain near-constant pH inside, under acid or base stress from outside. Most of what is currently understood on bacterial adaptation to changes in the external environment applies to aerated cultures grown in liquid medium under laboratory conditions. This research will identify how the bacterium Escherichia coli responds to acid stress and base stress under conditions found in natural environments, such as low oxygen and biofilms. Undergraduate researchers will employ fluorescence microscopy and laboratory evolution to address: (1) How do bacterial cells regulate pH as they divide and undergo polar aging? (2) How does pH stress cause oxidation stress (3) How do bacteria evolve under acid stress to grow at lower pH than the ancestral strain The answers to these questions will help the fermentation industry devise improved food preservatives and processes for biotechnology.
BROADER IMPACTS: The project will contribute to the nation's human resources by continuing a productive research program run by undergraduates. Each year, 10 first-year student researchers will be recruited from the Kenyon College STEM programs and science classes, as well as 2 high school students. Students will learn fundamental techniques of microbiological research while working with more advanced peers in BIOL 385 Research in Biology and BIOL 497 Senior Honors. They will write their own mini-proposals, design and conduct the experiments, and draft the manuscript for publication. Many undergraduates attracted to work on this project decide to pursue careers in science. Students will also serve as judges for the high-school science fair, and provide materials and demonstrations for members of an economically underserved community.
