Chemotactic-like response of Escherichia coli cells lacking the known chemotaxis machinery but containing overexpressed CheY
We describe a chemotactic-like response of Escherichia coli strains lacking most of the known chemotaxis machinery but containing high levels of the response regulator CheY. The bacteria accumulated in aspartate-containing capillaries, they formed rings on tryptone-containing semisolid agar, and the probability of counterclockwise flagellar rotation transiently increased in response to stimulation with aspartate (10−10–10−5 M; the response was inverted at > 10−4 M). The temporal response was partial and delayed, as was the response of a control wild-type strain having a high CheY level. α-Methyl-DL-aspartate, a non-metabolizable analogue of aspartate as well as other known attractants of E. Coli, glucose and, to a lesser extent, galactose, maltose and serine caused a similar response. So did low concentrations of acetate and benzoate (which, at higher concentrations, act as repellents for wild-type E. coli ). Other tested repellents such as indole, Ni2+ and Co2+ increased the clockwise bias. These observations raise the possibility that, at least when the conventional signal transduction components are missing, a non-conventional chemotactic signal transduction pathway might be functional in E. coli. Potential molecular mechanisms are discussed.
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Document Type: Research Article
Affiliations: The Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel.
Publication date: February 1, 1999