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 dur...

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Bibliographic Details
Published in:Biochemical journal 1995-03, Vol.306 ( Pt 3) (3), p.865-869
Main Authors: Watkins, N J, Knight, M R, Trewavas, A J, Campbell, A K
Format: Article
Language:English
Subjects:
Aequorin - genetics
Aequorin - pharmacology
Base Sequence
Calcium - metabolism
Chemotaxis - genetics
DNA Primers
Escherichia coli - genetics
Escherichia coli - metabolism
Molecular Sequence Data
Recombinant Proteins - genetics
Recombinant Proteins - pharmacology
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Summary: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.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj3060865