Compensatory role of the cis‐trans‐isomerase and cardiolipin synthase in the membrane fluidity of Pseudomonas putida DOT‐T1E

Abstract

In Gram-negative bacteria, cell membrane fluidity is influenced by phospholipid head group composition and linked fatty acids. Exposure of Pseudomonas putida to stressing agents results in short- and long-term modifications in membrane lipids. The main adaptive change observed in response to organic solvents in the short term is the cis- to trans-isomerization of unsaturated fatty acids in a reaction mediated by cis/trans-isomerase (CTI); whereas in the long term an increase in cardiolipin content takes place. Despite the interest of these genes in the context of stress responses, the transcriptional regulation of the cti and cls genes has not been studied before. The cti and cls (cardiolipin synthase) genes in the solvent-tolerant P. putida DOT-T1E strain form monocistronic units and are expressed from sigma-70 promoters. Expression from the cls promoter is sixfold higher in the stationary phase than in the log phase, and expression of the cls gene is not influenced by solvents. The cti gene is expressed at fairly constant levels in the log and stationary phase, but its level of expression is moderately upregulated in response to toluene. We used fluorescence polarization assays to show that mutants deficient in the cti gene exhibit less rigid membranes than the wild-type strain, whereas mutants with a knockout in the cls gene exhibit increased membrane rigidity. A double cti/cls mutant has similar membrane rigidity as the wild-type strain, which points towards a compensatory effect of the mutations with regard to membrane fluidity. However, the cls and cls/cti mutants were more sensitive to solvents than the wild-type and the cti mutant because of the impaired functioning of efflux drug transporters.

Bacterial cell membrane adaptation responses on stress caused with the environmental pollutants

“…Control experiment was performed without PCBs or 3-CBA, PCB0 -PCBs were added at the time of inoculation, PCB3 -PCBs were added to three-day cultivation, CBA0 -3-CBA was added at the time of inoculation, CBA3 -3-CBA was added to three-day cultivation. Effect of PCBs and 3-CBA on membrane adaptation Previous works described an increase in saturation of membrane phospholipids in the presence of toxic organic compounds as phenol, PAHs, and organic solvents (Heipieper et al 1994;Čertík et al 2003;Dercová et al 2004;Bernal et al 2007;Mrozik et al 2010). However, information about the effect of PCBs is rarely accessible.…”

Pentanol and Benzyl Alcohol Attack Bacterial Surface Structures Differently

“…It was suggested that organic solvents accumulate in cellular membranes and disorganize the structures, and the resultant losses of intracellular ions and metabolites lead to cell death (19,20). Organic solvents also induce various cellular responses, including structural changes of the membrane (21,22), and upregulation or downregulation of various other genes, as revealed by transcriptomic analyses (19,23). Nonetheless, with regard to the simultaneous addition of cationic agents and alcohols, many questions remain, such as how each agent acts individually on microbes.…”

Adaptation beyond the Stress Response: Cell Structure Dynamics and Population Heterogeneity in Staphylococcus aureus

“…3). Such multi-layered interconnected survival strategies, together with the general or specialized horizontal gene transfer systems (7,64), are key features in understanding how S. aureus has developed as such a successful pathogen.…”

“…A general strategy among bacteria is to change phospholipid composition in response to growth phase or environmental stress such as osmolality (74), pH (31,51), temperature and the presence of organic solvents (7,73). In the 1970's, the molecular mechanism of staphylococcal salt resistance was studied, focusing on a phospholipid, cardiolipin (CL), which constitutes about 30% of the cell membrane in the stationary phase of growth (80).…”