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 #64<br />
A NOVEL PAS-GGDEF-EAL PROTEIN INVOLVED IN REGULATION OF MOTILITY IN<br />
PSEUDOMONAS PUTIDA<br />
Herrera Seitz, K 1 and Shingler, V 2<br />
1 2<br />
IIB, FCEyN, Univ. Nac. del Mar del Plata, Molecular Biology Department, Umeå <strong>University</strong>,<br />
Sweden.<br />
Chemotaxis allows motile bacteria to respond to chemical gradients to relocate<br />
themselves near the source <strong>of</strong> nutrients. Soil Pseudomonads are known to be able to grow in a<br />
wide variety <strong>of</strong> carbon sources, including many that are considered environmentally toxic. Unlike<br />
previously characterized chemotactic responses in Pseudomonas strains, taxis <strong>of</strong> P. putida<br />
CF600 and P. putida KT2440 towards methyl-phenols is dependent upon its ability to<br />
metabolize the compound, rather than on a classical ligand-binding chemoreceptor. E. coli<br />
metabolism-dependent taxis responses are mediated by the Aer receptor that is closely related<br />
to chemoreceptors, but which contains a FAD-binding PAS sensory domain. P. putida<br />
possesses three aer-like genes. During analysis <strong>of</strong> the Aer-like receptors <strong>of</strong> P. putida, Aer-1 was<br />
found to be encoded in a dicistonic operon with PP2258, a PAS-GGDEF-EAL domain protein.<br />
Our attention was drawn to PP2258 because a null mutant was found to exhibit a general<br />
motility defect on solid, but not in liquid, media (Sarand et al., 2008).<br />
GGDEF- and EAL-domains are associated with diguanylate cyclase and<br />
phosphodiesterase activities that are involved in turnover <strong>of</strong> the near ubiquitous bacterial<br />
second messenger c-di-GMP. The levels <strong>of</strong> c-di-GMP can modify cells behavior and motility;<br />
therefore we reasoned that PP2258 link to motility via c-di-GMP signaling. As a first approach to<br />
test this idea, the biochemical properties <strong>of</strong> wild type and mutant derivatives <strong>of</strong> PP2258 were<br />
studied using over expression <strong>of</strong> the protein both in E. coli and P. putida.<br />
When PP2258 was over expressed in E. coli or P. putida cells, c-di-GMP levels were<br />
markedly increased compared to those <strong>of</strong> control cells, although accumulation <strong>of</strong> c-di-GMP was<br />
much lower in E. coli than in P. putida extracts. Alanine substitutions <strong>of</strong> the GGDEF domain<br />
associated with c-di-GMP synthesis causes a major decrease c-di-GMP accumulation, while an<br />
alanine substitution in EAL domain associated with c-di-GMP hydrolysis led to a >7-fold<br />
increase in accumulation. Together, these results suggest that PP2258 could be one <strong>of</strong> the rare<br />
examples <strong>of</strong> a dual GGDEF-EAL domain protein where both domains are catalytically active.<br />
References:<br />
Sarand, I., Österberg, S., Holmqvist, S., Holmfeldt, P. Skärfstad, E., Parale, R. E., & Shingler, V.<br />
(2008) Metabolism-dependent taxis towards (methyl)phenols is coupled through the most<br />
abundant <strong>of</strong> three polar localized Aer-like proteins <strong>of</strong> Pseudomonas putida. Environ.<br />
Microbiology. 10:1320-1334<br />
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