Abstract
Swarming is the most rapid surface motility allowing Pseudomonas aeruginosa bacteria to rapidly colonize new surfaces. However, swarming behavior is affected by environmental factors like ultraviolet irradiation (UVc). UVc radiation is the most disinfection technology usually applied for wastewater and proven to be effective to inactivate microorganisms. However, efficiency against motile bacteria is not yet studied. This study aims to explain the mechanisms of resistance of swarmer P. aeruginosa cells toward UVc exposure. P. aeruginosa liquid cultures were allowed to swarm across a semisolid surface for 18 h and directly exposed to UVc radiations. Emergent swarmer colonies, revealed after re-incubation, were selected to study biofilm formation, fatty acid (FA) composition, and ultrastructure. Our results showed that membrane adaptation to UVc radiations was seen in Pseudomonas cells by an increase of cyclic fatty acid (CFA) content, confirming the role of cyclopropane in radio-resistance of swarmer cells. Furthermore, electron microscopic study confirmed that over production of S-layer is believed to be a protective form adopted by P. aeruginosa swarmer cells to resist after 5 min of UVc exposure. Moreover, membrane disintegration is the lethal effect observed after 15 min of UVc exposure. In the other hand, study of biofilm production showed an enhancement of biofilm formation, of swarmer cells mainly after 15 min of UVc exposure. There results confirmed that swarming process is highly correlated with particular FA composition of P. aeruginosa membrane and that radio-resistance of swarmer cells is highly supported by CFA biosynthesis and S-layer overproduction.
Highlights
Pseudomonas aeruginosa is adept at coordinating individual cells to contribute in some surfaceassociated behaviors
For prolonged exposure time (15 min), we noticed a narrowing of the migration surface accompanied with the emergence of multiple resistant colonies (Figure 1A-T15)
Our results showed that untreated P. aeruginosa swarmer cells were unable to produce biofilm on the air–liquid interface of glass tubes
Summary
Pseudomonas aeruginosa is adept at coordinating individual cells to contribute in some surfaceassociated behaviors. Swarming motility involves synchronized and Pseudomonas Swarmer Cells Exposed to UVc fast movement of a bacterial population across a semisolid surface (Fraser and Hughes, 1999). This movement is frequently typified by a dendritic colonial appearance. Rhamnolipids are supposed to enable swarming cells to surmount the surface tension of the water, in swarming media (Overhage, 2008). This form of motility is an early state in biofilm formation and is extremely important in the structuring of the biofilm. The linkage between biofilm formation and motility tends to be multifaceted because both processes involve similar components
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