Sensory Adaptation and Chemotaxis in Bacillus Subtilis

178 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.Bacterial chemotaxis is the process by which bacteria sense chemicals in their environment and respond to them by migrating up attractant gradients or down repellent gradients. Bacteria in isotropic medium alternately swim smoothly or tumble. Swimming is correlated with counterclockwise rotation of the flagella (as viewed down the flagellum toward the cell body), and tumbling is correlated with clockwise rotation of the flagella. When a chemical attractant is added to a suspension of bacteria, one observes an increase in the length of time that the bacteria swim. The opposite occurs upon addition of repellents. After this initial response, the bacteria resume their prestimulus behavior even though the chemical stimulus is still present. This phenomenon is referred to as adaptation.This thesis investigates the role protein methylation plays in the response of Bacillus subtilis to amino acid attractants. By performing in vivo methylation experiments, the effects of amino acids on the methylation profiles of B. subtilis methyl-accepting chemotaxis proteins (MCPs) was investigated. Both increases and decreases have been found to occur in the level of methylation of these proteins. By using Conway diffusion cells, one can correlate the demethylation event with the adaptation process. Gas chromatography indicates that methanol is evolved upon demethylation of these proteins. As more attractant receptors are titrated, corresponding increases in methanol evolution result. During the period of increased methanol production, bacteria swim smoothly. The methylesterase responsible for this demethylation has been purified and an in vitro system has been developed to study attractant effects on protein methylation. A calcium binding substance has also been partially purified that influences the methylation reactions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD