Study On The Interplay Between Myxococcus Xanthus And Pseudomonas Aeruginosa

Pseudomonas aeruginosa and Myxococcus xanthus as model environmental strains,both have excellent surface motilities,and could produce extracellular matrix to regulate their motility behavior and biofilm formation.Although a large amount of work has been done,our understanding on how they might interact each other is still far from complete.In this work,by employing bacterial tracking techniques,we try to get a better understanding on the interplay between these two species from two aspects: one is whether and how the exopolysaccharides(EPS)of Myxococcus xanthus can affect the surface motility of Pseudomonas aeruginosa,and the other is the predation of Myxococcus xanthus on Pseudomonas aeruginosa.To investigate the effect of EPS of Myxococcus xanthus on Pseudomonas aeruginosa surface movement,we first prepare EPS-modified and Psl-modified glass surfaces by incubating Myxococcus xanthus DK1622 and Pseudomonas aeruginosa,respectively,on the surface for a while,which is then followed by getting rid of the cells from the surface.Then new injected Pseudomonas aeruginosa cells are monitored in situ on the modified surfaces using high-throughput cell-tracking techniques.The results show that compared with the case of bare glass surfaces,when Pseudomonas aeruginosa cells move on the EPS-modified glass surfaces,the speed of surface movement and the surface expansion are reduced,and the resulted trajectories of cells are more concentrated.Moreover,compared with Psl knockout strain ?pslBCD,it seems that wild-type PAO1 is more affected by EPS-modified surfaces,which indicates that Psl has a role in mediating the interaction between EPS and bacterial cell bodies.As a control,we also studied the motility behavior of Pseudomonas aeruginosa on Psl-modified glass surface.Similarly,the results show that the surface movement of P.aeruginosa cells are confined on Psl-modified glass surfaces,but contrary to the case of EPS-modified glass surfaces,?pslBCD is more affected by Psl-modified surfaces than WT PAO1.These results further support that Psl helps mediating the interaction between EPS and cell bodies.To further illustrate the role of Psl,we observed Psl response deficient strain ? sia D movement on Psl-modified glass surfaces and found that there is little difference in the surface movement of ?sia D on bare glass surfaces and Psl-modified glass surfaces,which agrees with the results of earlier studies.Simultaneously,we studied the predatory behavior of Myxococcus xanthus DK1622 on Pseudomonas aeruginosa PAO1 both at single-cell and collective level.By analyzing the single cell behavior of Myxococcus xanthus,we found that Myxococcus xanthus cells displayed reduced speed,more curved trajectories and more frequent change of moving directions during prey,which quantify the influcence of physical contact for prey.Using the mutants of Myxococcus xanthus including motility mutants(A+S-,A-S+)and antibiotic TA mutant(TA-),we further studied the roles of motility as well as TA in the predation,and the results show that motility ability affects the predation more than TA does.