Chemosensory and thermosensory excitation in adaptation-deficient mutants of Escherichia coli.
Methyl-accepting chemotaxis protein-methyltransferase-deficient mutants, cheR mutants, of Escherichia coli showed a tumble response to repellents only at low temperatures, and the resultant tumbling lasted unless the condition was changed. The swimming pattern of the repellent-treated cells was different at different temperatures, indicating that the absolute temperature is a determinant of the tumbling frequency of those cells. The tumbling of those cells was also suppressed by the addition of attractants. Under a suitable repellent concentration, the tumbling frequency of the cells was found to be simply determined by the ligand occupancy of chemoreceptors for many attractants. In a methyl-accepting chemotaxis protein-methylesterase-deficient mutant, a cheB deletion mutant, the tumbling frequency was also determined by receptor occupancy of some attractants. These results indicate that in the adaptation-deficient mutants, sensory signals are produced in proportion to the amount of ligand-bound or of thermally altered receptors and transmitted to the flagellar motors without any modification. Thus, it is concluded that the adaptation system, namely, the methylation-demethylation system of methyl-accepting chemotaxis proteins, is not concerned with the step of chemosensory or thermosensory excitation. A simple model is proposed to explain how the swimming pattern of the adaptation-deficient mutants is determined.
D001426:Bacterial Proteins; D002465:Cell Movement; D002630:Chemotactic Factors / Q000235:genetics*; D002633:Chemotaxis; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development*; D008565:Membrane Proteins / Q000235:genetics*; D000072236:Methyl-Accepting Chemotaxis Proteins; D009154:Mutation; D011496:Protein Methyltransferases / Q000235:genetics*; D013045:Species Specificity; D013696:Temperature
D001426:Bacterial Proteins; D002630:Chemotactic Factors; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011496:Protein Methyltransferases