Time-resolved polarized fluorescence studies of the temperature adaptation in Bacillus subtilis using DPH and TMA-DPH fluorescent probes.
The validity of the concept of homeoviscous adaptation was tested for bacteria Bacillus subtilis. The Bacillus subtilis grown at 20 degrees C (referred to as Bs20) exhibit a considerable increase of branched anteiso-C15, the major fatty acid component of membrane lipids, relative to membranes grown at 40 degrees C (Bs40). The time-resolved fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) showed that these changes in the lipid composition are accompanied by changes in a mean lipid order. In particular, the DPH order parameters <P2> and <P4> measured in Bs20 membranes at 18 degrees C and in Bs40 membranes at 45 degrees C, respectively, tend to be equal. This effect was less pronounced for TMA-DPH. Our observations suggest that a physical parallel to the changes of lipid composition is the maintenance of an optimal lipid order in the hydrophobic core of the cytoplasmic membranes. It can be interpreted as a tendency of Bacillus subtilis to keep the lateral pressure in its membranes at an optimal value, independent of the temperature of cultivation.
Herman
P
P
Department of Biophysics, Charles University, Prague, Czech Republic.
Konopásek
I
I
Plásek
J
J
Svobodová
J
J
D000222:Adaptation, Physiological; D001412:Bacillus subtilis / Q000502:physiology*; D004161:Diphenylhexatriene / Q000031:analogs & derivatives; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D013696:Temperature
D005456:Fluorescent Dyes; D004161:Diphenylhexatriene