Potentiation, desensitization, and inversion of response in bacterial sensing of chemical stimuli.

Abstract

Behavior patterns of chemotactic mutants of Salmonella typhimurium were compared to those of the wild type by using the quantitative tumble frequency assay. Some cheU mutants were completely inverted in their responses, e.g., attractants produce responses expected for repellents and repellents produce responses expected for attractants. Still others swam smoothly and did not respond to any stimuli. Mutants of other complementation groups exhibited exact additivity or potentiation in response to multiple stimuli but the wild type showed desensitization. The cheU gene product apparently acts as a switch at the interface between the sensing system and the motor response. The system is finely tuned so that changes in individual proteins can produce potentiation, desensitization, exact additivity or inversion of responses.