?The molecular logic of cold sensing in bacteria?

DIEGO DE MENDOZA

Cuatro Cienegas

Congreso; Tercer Congreso de Bioquimica y Biologia Molecular de Bacterias; 2013

Conferencia Plenaria The ability of bacteria to control the biophysical properties of their membrane phospholipids allows them to thrive in a wide range of physical environments. When bacteria are exposed to temperatures below those of their normal conditions, the lipids of their membrane become rigidified, leading to a suboptimal functioning of cellular activities. These organisms can acclimate to such new conditions by an increase in the desaturation of the acyl chain of membrane phospholipids. Phospholipids containing unsaturated fatty acids have a much lower transition temperature than those lipids made of saturated fatty acids. As a result, the physical properties (fluidity) of the membrane lipids return to their original state, or close to it, with restoration of normal cell activity at the lower temperature. We discovered that in the model Gram-positive bacterium Bacillus subtilis the transcription of the gen des, coding for an acyl lipid desaturase, is controlled by a biological thermometer that senses changes in the membrane properties due to abrupt temperature change. This thermosensor, named DesK, is a bifunctional histidin kinase/phosphatase that senses membrane biophysical properties and transmits this signal to the transcriptional apparatus. In this talk, experimental evidence for the regulation of the distinct DesK catalytic mechanisms and for signal transduction through the membrane to the cytoplasmic domain will be discussed.