Free calcium transients in chemotactic and non-chemotactic strains of Escherichia coli determined by using recombinant aequorin.
Intracellular Ca2+ has been previously implicated in the chemotactic response of Escherichia coli. However, no correlative measurements of intracellular free Ca2+ have been made during bacterial chemotaxis, essential if this is to be established. In order to monitor internal free Ca2+ in E. coli during challenge with chemotactic agents, the Ca(2+)-activated photoprotein aequorin was expressed in a chemotactic strain (AB1157) and a non-chemotactic strain [BL21(DE3)] of E. coli. Repellents were found to cause an increase (50-150 nM) in intracellular free Ca2+, whereas attractants caused a small but consistent decrease in intracellular free Ca2+. These data are in agreement with the proposed model that an increase in intracellular free Ca2+ causes tumbling. The effect of increasing external Ca2+ on the regulation of intracellular free Ca2+ in both strains was monitored by using aequorin. The resting level of free Ca2+ in E. coli (AB1157) was found to be 100 nM, which agrees with previous data [Gangola and Rosen (1987) J. Biol. Chem. 262, 12570-12574]. As these results also show differences in the regulation of intracellular free Ca2+ between the two strains in the presence of high external Ca2+ concentrations, this may have implications for the effect of high-Ca2+ environments on E. coli.
Watkins
N J
NJ
Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff, U.K.
Knight
M R
MR
Trewavas
A J
AJ
Campbell
A K
AK
D000331:Aequorin / Q000235:genetics / Q000494:pharmacology*; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002633:Chemotaxis / Q000235:genetics; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology
D017931:DNA Primers; D011994:Recombinant Proteins; D000331:Aequorin; D002118:Calcium