Department of Microbiology, University of Illinois, Urbana, IL 61801, USA.
Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA.
Environ Microbiol. 2019 May;21(5):1659-1676. doi: 10.1111/1462-2920.14546. Epub 2019 Mar 12.
One key to the success of Pseudomonas spp. is their ability to reside in hostile environments. Pseudomonas spp. possess a cis-trans isomerase (Cti) an enzyme that converts the cis-unsaturated fatty acids (FAs) 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 Pseudomonas 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 FAs was found to decrease after 24 h of growth. Although this decrease was accompanied by an increase in cyclopropane FA content, this was not at the expense of trans-unsaturated FAs demonstrating the absence of competition between Cti and Cfa in FA modification.
铜绿假单胞菌成功的一个关键是其能够在恶劣环境中生存。铜绿假单胞菌具有顺反异构酶（Cti），这是一种酶，可以将膜脂中的顺式不饱和脂肪酸（FAs）转化为其反式异构体，从而使膜变硬，抵抗应激。虽然已经报道了翻译后 Cti 的调节，但转录 Cti 调节仍需要更详细地研究。在这里，我们研究了溶剂耐受菌株铜绿假单胞菌 F1 中的 cti 转录调节。鉴定了两个 cti 转录起始位点（cti-279 和 cti-77），cti-279 转录本占主导地位。发现 cti 的表达随温度升高、有机溶剂辛醇的添加和静止生长阶段而增加。我们发现 cti 的表达受到环腺苷酸受体蛋白（Crp）的抑制，抑制作用需要 Crp 的环腺苷酸配体。在生长 24 小时后，发现反式不饱和 FAs 的产量下降。尽管这种减少伴随着环丙烷 FA 含量的增加，但这并不是以牺牲反式不饱和 FAs 为代价的，这表明 Cti 和 Cfa 在 FA 修饰中不存在竞争。
