Implication of Mn-cofactored superoxide dismutase in the tolerance of swarmer Pseudomonas aeruginosa to polymixin, ciprofloxacin and meropenem antibiotics.

The protective role of superoxide dismutase (Sod) against oxidative stress, resulting from the common antibiotic pathway of action, has been studied in the wild type and mutant strains of swarmer Pseudomonas aeruginosa, lacking Cytosolic Mn-Sod (sodM), Fe-Sod (sodB) or both Sods (sodMB).Our results showed that inactivation of sodB genes leads to significant motility defects and tolerance to meropenem. This resistance is correlated with a greater membrane unsaturation as well as an effective intervention of Mn-Sod isoform, in antibiotic tolerance.Moreover, loss of Mn-Sod in sodM mutant, leads to polymixin intolerance and is correlated with membrane unsaturation. Effectivelty, sodM mutant showed an enhanced swarming motility and a conserved rhamnolipid production. Whereas, in the double mutant sodMB, ciprofloxacin tolerance would be linked to an increase in the percentage of saturated fatty acids in the membrane, even in the absence of superoxide dismutase activity.The overall results showed that Mn-Sod has a protective role in the tolerance to antibiotics, in swarmer P.aeruginosa strain. It has been further shown that Sod intervention in antibiotic tolerance is through change in membrane fatty acid composition.

Damage of the swarmer Pseudomonas soil isolate cell by UVc as revealed by transmission electron microscopy.

The modeling of the response of living organisms to a change in environment is an important issue of current interest. An example is the effect of ultraviolet radiation on biological systems. In this paper, molecular and analytical identification of Pseudomonas isolate were reported. Then, swarmer Pseudomonas cells were exposed to UVc radiations. The spatiotemporal response of swarmer Pseudomonas, to UVc exposure, was followed. Observing alterations in bacterial membrane integrity by electron microscopy can help to clarify the detailed mechanisms of resistance to UVc. The most evident changes were related to membrane structures. In the cytoplasm, the main finding was the appearance of round mesosomes as intracellular bilayered membranes. Another impact of UVc on Pseudomonas was evident from the appearance of additional membrane structures. In accordance with the viability results, UVc-induced ultrastructural changes of Pseudomonas membrane structures were identified, resulting in cell death, through a multistage model of UVc inactivation.