Watkins N J, Knight M R, Trewavas A J, Campbell A K
Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff, U.K.
Biochem J. 1995 Mar 15;306 ( Pt 3)(Pt 3):865-9. doi: 10.1042/bj3060865.
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.
此前已有研究表明细胞内钙离子与大肠杆菌的趋化反应有关。然而，在细菌趋化过程中尚未进行细胞内游离钙离子的相关测量，而若要确定这一关系，此类测量必不可少。为了在趋化剂刺激期间监测大肠杆菌细胞内的游离钙离子，在大肠杆菌的趋化菌株（AB1157）和非趋化菌株[BL21(DE3)]中表达了钙离子激活的光蛋白水母发光蛋白。研究发现，驱避剂会导致细胞内游离钙离子增加（50 - 150 nM），而吸引剂则会使细胞内游离钙离子出现小幅但持续的下降。这些数据与细胞内游离钙离子增加会导致翻滚的模型一致。通过使用水母发光蛋白监测了增加外部钙离子对两种菌株细胞内游离钙离子调节的影响。发现大肠杆菌（AB1157）中游离钙离子的静息水平为100 nM，这与先前的数据[Gangola和Rosen（1987年）《生物化学杂志》262卷，12570 - 12574页]相符。由于这些结果还显示在高外部钙离子浓度下两种菌株在细胞内游离钙离子调节方面存在差异，这可能对高钙离子环境对大肠杆菌的影响具有启示意义。
