Transcriptional regulation of fatty acid cis-trans isomerization in the solvent-tolerant soil bacterium, Pseudomonas putida F1.

One key to the success of Pseudomonas spp. is their ability to reside in the hostile environments. Pseudomonas spp. possess a cis-trans isomerase (Cti) an enzyme that converts the cis-unsaturated fatty acids of the membrane lipids to their trans-isomers to rigidify the membrane and thereby resist stresses. Whereas the posttranslational Cti regulation has been previously reported, transcriptional cti regulation remains to be studied in more details. Here, we have studied cti transcriptional regulation in the solvent-tolerant strain P. putida F1. Two cti transcriptional start sites (cti-279 and cti-77) were identified with cti-279 transcript being dominant. Expression of cti was found to increase with temperature increase, addition of the organic solvent, octanol and in the stationary growth phase. We found that cti expression was repressed by the cyclic-AMP receptor protein (Crp) and repression required the cyclic-AMP ligand of Crp. Production of trans- unsaturated fatty acids was found to decrease after 24 h of growth. Although this decrease was accompanied by an increase of cyclopropane fatty acid content, this was not at the expense of trans-unsaturated fatty acids demonstrating the absence of competition between Cti and Cfa in fatty acid modification. This article is protected by copyright. All rights reserved.