Slow changes in cytosolic free Ca2+ in Escherichia coli highlight two putative influx mechanisms in response to changes in extracellular calcium

Jones, Helen E., Holland, I. B., Baker, Helen Louise and Campbell, Anthony Keith 1999. Slow changes in cytosolic free Ca2+ in Escherichia coli highlight two putative influx mechanisms in response to changes in extracellular calcium. Cell Calcium 25 (3) , pp. 265-274. 10.1054/ceca.1999.0028

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Abstract

Free intracellular Ca2+([Ca2+]i) inEscherichia coliwas measured using the bioluminescent protein aequorin. Overall, the bacteria maintained a tight control on their free [Ca2+]i. The results indicated a slow Ca2+influx, the magnitude of the initial rise in free [Ca2+]ibeing dependent upon the concentrations of external Ca2+. This was followed by the slow removal of free Ca2+until normal levels were restored. Specifically, addition of external Ca2+(0.25–10 mM) resulted in a gradual rise in intracellular free Ca2+from a basal level of approximately 272 nM, maximally reaching a peak of 0.85–5.4 μM within 30–40 min. This was followed by a slow fall over the next 30 min, culminating in an oscillatory pattern of free [Ca2+]i(range 0.3–0.7 μM for 0.25 mM external Ca2+). In the presence of EGTA, free [Ca2+]iwas dramatically reduced. Neither the influx of Ca2+nor restoration of intracellular free Ca2+required protein synthesis. Moreover, preincubation with Ca2+increased the rising phase of intracellular Ca2+in response to further exposure to external Ca2+. This was further evidence against a specific adaptation process such as the synthesis of calcium exporters. A putative Ca2+influx channel was demonstrated in stationary phase cells in particular, which could be blocked by La3+. This channel was consistent with the voltage-activated poly-3-hydroxybutyrate/polyphosphate Ca2+channels previously detailed by Reusch et al. [23] Even in the presence of La3+, however, the free [Ca2+]iof log phase and stationary phase bacteria still increased two-fold over resting values in response to external Ca2+. This suggested the presence of at least two Ca2+influx processes, one inhibited by La3+and the other not.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences Medicine Pharmacy
Subjects:	Q Science > QD Chemistry R Medicine > RM Therapeutics. Pharmacology
Publisher:	Elsevier
ISSN:	0143-4160
Last Modified:	05 Feb 2020 03:32
URI:	https://orca.cardiff.ac.uk/id/eprint/22523

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