Thermosensory transduction in Escherichia coli: inhibition of the thermoresponse by L-serine.

Information processing of the thermoresponse in Escherichia coli was compared with that of the chemoresponse. Competition experiments between various chemical stimuli and the thermal stimulus showed that only L-serine was a potent inhibitor of the thermosensory transduction. The concentration of L-serine necessary for complete inhibition of the thermoresponse was about 0.1 mM. L-Serine at this concentration did not inhibit chemoresponses to many amino acids. Pleiotropic aspartate-taxis mutants (tar) showed normal thermoresponse but pleiotropic serine-taxis mutants (tsr) showed decreased or almost no thermoresponse. These results suggest that the thermosensory transducing system in E. coli has an intimate interaction with the chemosensory transducing pathway specific for L-serine. A simple model for the thermosensory transduction is discussed.