Abstract
We studied the mechanism of cold adaptation in B. subtilis under anaerobic conditions. We found that in anaerobiosis the induction of des expression after temperature downshift was not downregulated.
However, the transfer to aerobic conditions rapidly restored the downregulation. Under both conditions, the induction of des expression was substantially reduced by the addition of external fluidizing oleic acid and was fully dependent on the DesK-DesR regulatory system.
There was no desaturation after des induction under anaerobic conditions despite the presence of high levels of the des protein product. The cold adaptation of B. s. in anaerobiosis is therefore mediated exclusively by the increased anteiso/iso ratio of branched-chain fatty acids and not by the temporarily increased level of unsaturated fatty acids that is typical under aerobic conditions.
The degrees of membrane fluidization (DPH fluorescence anisotropy) were found to be similar under both aerobic and anaerobic conditions.