Some simple single-celled organisms provide models for understanding complex biological problems. In sensory neuroscience, one of the areas important to understand is the process of transduction, in which capture of some form of stimulus is transformed into a cellular signal of some kind. In chemosensory transduction, for example smell, an odor molecule binds with a particular receptor protein on the membrane of the olfactory sensory cell, and internal biochemical reactions lead to the sending of a nerve impulse to the brain. This project continues work on the common bacterium E. coli, as a model system for chemoreception. This unicellular organism lives in liquid medium, and propels itself toward attractant chemicals like nutrients, and away from others. It has been found that the mechanism for this chemically-cued movement, called chemotaxis, depends in part on the role of calcium ions in solution. Calcium ions are known to be extremely important in other cellular signaling systems, including between nerve cells. This project combines biochemical work with genetic mutant strains of bacteria to test steps in the chemotactic response for calcium sensitivity, to find out how changes in local calcium concentration affect the chemotaxis, and to see whether pharmacological agents that block calcium responses in other systems work the same way in bacteria. Results are important beyond simply bacterial chemotaxis because they are highly relevant to understanding sensory transduction in general, and to understanding how calcium can exert important and widespread effects in more complex systems.
