POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
<strong>BLAST</strong> X Poster #18<br />
CYTOCHROME d BUT NOT CYTOCHROME o RESCUES THE TOLUIDINE BLUE GROWTH<br />
SENSITIVITY OF arc MUTANTS IN E. COLI<br />
Adrián F. Alvarez, Roxana Malpica, Martha Contreras, Edgardo Escamilla, Everardo Ramírez<br />
and Dimitris Georgellis.<br />
Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional<br />
Autónoma de México, 04510 México D.F., México<br />
The Arc (anoxic redox control) two-component signal transduction system, consisting <strong>of</strong><br />
the ArcB sensor kinase and the ArcA response regulator, allows adaptive responses <strong>of</strong><br />
Escherichia coli to changes <strong>of</strong> O2 availability. Under anaerobic conditions, the ArcB sensor<br />
kinase autophosphorylates and then transphosphorylates ArcA, which in this form acts as a<br />
global transcriptional regulator that controls the expression <strong>of</strong> many operons involved in<br />
respiratory or fermentative metabolism. Under aerobic conditions, the system is inactivated<br />
through the inhibition <strong>of</strong> the kinase activity <strong>of</strong> ArcB by the quinone electron carriers, and the<br />
subsequent ArcA dephosphorylation. The arcA gene was previously known as the dye gene<br />
because null mutants were growth sensitive to the photosensitizer redox dyes toluidine blue and<br />
methylene blue, a phenotype whose molecular basis still remains elusive. Toluidine blue is a<br />
redox dye that, in presence <strong>of</strong> light, allows the production <strong>of</strong> reactive oxygen species (ROS). In<br />
this study we report that the toluidine blue O effect on the arc mutants is light independent, and<br />
only observed during aerobic growth conditions. Moreover, seventeen suppressor mutants with<br />
restored growth were generated and analyzed. Thirteen <strong>of</strong> those possessed insertion elements<br />
(IS) upstream the cydAB operon, rendering its expression ArcA independent. Finally, it was<br />
found that, in contrast to cythocrome d, cythocrome o was not able to confer toluidine blue<br />
resistance to arc mutants, thereby representing an intriguing difference between the two<br />
terminal oxidases.<br />
69