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The use of flash photolysis for a high‐resolution temporal and spatial analysis of bacterial chemotactic behaviour: CheZ is not always necessary for chemotaxis
Author(s) -
Dowd John P.,
Matsumura Philip
Publication year - 1997
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1997.4631830.x
Subject(s) - chemotaxis , biology , flash (photography) , mutant , escherichia coli , bacteria , flash photolysis , biophysics , gene , biological system , microbiology and biotechnology , genetics , physics , kinetics , optics , receptor , quantum mechanics , reaction rate constant
The purpose of this work was to develop a high‐resolution analysis of behaviour as an assay of the physiological consequences of mutations in the che genes and also to examine the role of CheZ in chemotaxis. Recent advances in flash photolysis have made it possible to expose cells to an unstable chemical gradient created by a square‐wave increase in attractant concentration. The response of individual cells can be tracked in the order of milliseconds using real‐time motion analysis. The tumble frequency of wild‐type Escherichia coli exposed to photoreleased aspartate falls very quickly to smooth‐swimming levels, and the swimming speed of these cells rises. As a consequence of these behavioural changes, there is an increase in the number of bacteria present in the centre of the flashed area, that is the bacteria’s response to the transient gradient generated by flash photolysis was to swim into the centre of the flash area. This allowed the rapid quantitative measurement of chemotaxis. Deletion of various che genes resulted in predictable changes in chemotactic behaviour. cheZ null mutants are non‐chemotactic when measured by classical techniques but demonstrate a definite chemotactic response to photoreleased attractant.