The use of flash photolysis for a high‐resolution temporal and spatial analysis of bacterial chemotactic behaviour: CheZ is not always necessary for chemotaxis

Abstract

SummaryThe 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.

The CheZ Binding Interface of CheA S Is Located in α-Helix E

“…2). The RCD values for the complemented ⌬cheA strain were in the range from 600 to 800 degrees/s, as seen previously with wild-type bacteria (3,7). RP1616 (⌬cheZ) showed tumbling behavior (RCD, ϳ1,500 degrees/s) (Fig.…”

“…The dephosphorylation of CheY is enhanced by CheZ (the CheY phosphatase) and CheA S (20). Cells lacking CheZ fail to respond appropriately to attractant stimuli (3). It is known that CheZ localization to the polar chemoreceptor clusters requires CheA S (2,17).…”

Role of motility and chemotaxis in the pathogenesis of Dickeya dadantii 3937 (ex Erwinia chrysanthemi 3937)

“…However, it has been reported that a cheB mutant of Azospirillum brasilense showed a reduced chemotactic response (Stephens et al, 2006). Interestingly, Dowd & Matsumura (1997), using a flash photolysis technique, demonstrated that an E. coli cheZ mutant (which is non-chemotatic by classical techniques) retains partial chemotaxis ability; these authors hypothesized that this is a consequence of the spontaneous dephosphorylation of CheY.…”

Identification of a chemotaxis gene region from Pseudomonas putida

“…CheZ is not always required for chemotaxis to occur in E. coli [11]. Three orfs were identi¢ed upstream of cheY.…”