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 #23<br />
THE Cyclic-di-GMP RECEPTOR PROTEIN YcgR LOCALIZES TO THE FLAGELLAR BASAL<br />
BODY AND CHANGES MOTOR BIAS IN SALMONELLA<br />
Vincent Nieto* and Rasika Harshey<br />
Section <strong>of</strong> Molecular Genetics and Microbiology, <strong>University</strong> <strong>of</strong> Texas at Austin, Texas 78712<br />
Cyclic-di-GMP (cdG) is a bacterial second messenger that plays a central role in the<br />
transition between motile and sessile states. In Salmonella enterica, absence <strong>of</strong> the cdG<br />
phosphodiesterase YhjH is known to elevate cdG levels, inhibit motility, and promote bi<strong>of</strong>ilm<br />
formation. YcgR, a cdG -binding protein, is required for this phenomenon. We show in this study<br />
that the absence <strong>of</strong> YhjH inhibits chemotaxis, and that this inhibition is more pronounced when<br />
YcgR is overexpressed from a plasmid. In liquid media, the bacteria were predominantly smooth<br />
swimming. Tethering experiments showed a pronounced shift to CCW rotation with a significant<br />
slowing <strong>of</strong> motor rotation. Inhibition <strong>of</strong> chemotaxis was therefore at the level <strong>of</strong> either production,<br />
or activity <strong>of</strong> the chemotaxis response regulator CheY~P, which acts at the switch to change the<br />
default CCW bias to CW. Expression <strong>of</strong> a GFP-tagged cdG-binding protein YcgR in a yhjH<br />
mutant background, resulted in punctate fluorescent dots along the cell membrane. Presence <strong>of</strong><br />
the puncta was dependent on the presence <strong>of</strong> flagellar basal bodies, but not on presence <strong>of</strong><br />
chemotaxis signaling components, suggesting that YcgR inhibits chemotaxis by acting at the<br />
switch. Inhibition <strong>of</strong> chemotaxis may represent a novel strategy to prepare for a sedentary<br />
existence by disfavoring migration away from a substrate on which a bi<strong>of</strong>ilm is to be formed.<br />
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