The thermal impulse response of Escherichia coli
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Edited by Howard C. BergHarvard UniversityCambridgeMA approved January 82008 (received for review October 18, 2007)
Abstract
Swimming Escherichia coli responds to changes in temperature by modifying its motor behavior. Previous studies using populations of cells have shown that E. coli accumulate in spatial thermal gradients, but these experiments did not cleanly separate thermal responses from chemotactic responses. Here we have isolated the thermal response by studying the behavior of single, tethered cells. The motor output of cells grown at 33°C was measured at constant temperature, from 10° to 40°C, and in response to small, impulsive increases in temperature, from 23° to 43°C. The thermal impulse response at temperatures < 31°C is similar to the chemotactic impulse response: Both follow a similar time course, share the same directionality, and show biphasic characteristics. At temperatures > 31°C, some cells show an inverted response, switching from warm- to cold-seeking behavior. The fraction of inverted responses increases nonlinearly with temperature, switching steeply at the preferred temperature of 37°C.
Footnotes
- †To whom correspondence should be addressed. E-mail: wsryu{at}princeton.edu
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Author contributions: W.S.R. and E.P. designed research; E.P. performed research; and W.S.R. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
- © 2008 by The National Academy of Sciences of the USA
