POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Poster #31<br />
THERMOSENSING FUNCTION OF Aer, A REDOX SENSOR OF E. COLI<br />
So-ichiro Nishiyama 1 , Shinji Ohno 2 , Noriko Ohta 3 , Akihiko Ishijima 4 1, 5<br />
and Ikuro Kawagishi<br />
1<br />
Department <strong>of</strong> Frontier Bioscience, Faculty <strong>of</strong> Bioscience and Applied Chemistry, Hosei<br />
<strong>University</strong><br />
2<br />
Department <strong>of</strong> Material Chemistry, Faculty <strong>of</strong> Engineering, Hosei <strong>University</strong><br />
3<br />
Division <strong>of</strong> Biological Science, Graduate School <strong>of</strong> Science, Nagoya <strong>University</strong><br />
4<br />
Institute <strong>of</strong> Multidisciplinary, Research for Advanced Materials, Tohoku <strong>University</strong><br />
5<br />
Department <strong>of</strong> Frontier Bioscience, Faculty <strong>of</strong> Engineering, Hosei <strong>University</strong><br />
Some motile bacteria can sense temperature and move to temperatures best-suited to<br />
growth. This behavior, called thermotaxis, has been extensively studied in Escherichia coli.<br />
Our early studies revealed that E. coli thermotaxis is mediated by chemoreceptors that also<br />
sense amino acids or sugars: Tsr (serine), Tar (aspartate and maltose) and Trg (ribose and<br />
galactose) function as warm sensors, producing counter-clockwise or clockwise flagellar rotation<br />
signals upon temperature upshift and downshift, respectively. Tap (dipeptides, pyrimidines)<br />
functions as a cold sensor, producing CW and CCW signals upon temperature increases and<br />
decreases, respectively. Unique among these temperature sensors, Tar switches from a warm<br />
sensor to a cold sensor after adaptation to its ligand, aspartate. Intensive studies <strong>of</strong> Tar<br />
revealed that the receptor’s transmembrane and methylation domains play important roles in<br />
thermotactic responses, but what part <strong>of</strong> the chemoreceptor molecule actually senses<br />
temperature, remains unknown.<br />
In this study, we found that the aerotaxis transducer Aer also has temperature-sensing<br />
ability. An otherwise receptor-less strain expressing only aer showed extremely smooth<br />
swimming and did not show any thermoresponse. However, after imposing a CW rotational<br />
bias by adding the general repellent, glycerol (up to 10% w/v) or by co-expressing a cytoplasmic<br />
fragment <strong>of</strong> Tar that does not mediate a thermoresponse, the cells showed CCW and CW<br />
responses to temperature upshifts and downshifts, respectively. These results suggest that Aer<br />
functions as a warm sensor, even though, unlike the Tar, Tap, Tsr, and Trg chemoreceptors,<br />
Aer does not have a periplasmic ligand-binding domain. Thus, temperature sensing by E. coli<br />
chemoreceptors may be a general attribute <strong>of</strong> their highly-conserved cytoplasmic signaling<br />
domain (or their less conserved transmembrane domain).<br />
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