Analysis of the swimming activity of Pseudomonas aeruginosa by using photonic force microscope

Swimming activity of flagella is a main factor of the motility of bacteria. Flagella expressed on the surface of bacterial species serve as a primary means of motility including swimming. We propose to use optical tweezers to analyze the swimming activity of bacteria. The sample bacteria in this work are Pseudomonas aeruginosa, and it is a gram-negative bacterium and it often causes leading to burn wound infections, urinary-tract infections, and pneumonia. The single polar flagellum of P. aeruginosa has been demonstrated to be important virulence and colonization factor of this opportunistic pathogen. We demonstrate a gene to regulate the bacterial swimming activity in P. aeruginosa PAO1 by biological method. However, the change of flagellar morphology was not observed by electron microscopy analysis, suggesting that the gene regulates the flagellar rotation that could not be detected by biological method. Photonic Force Microscope (PFM) first developed by E. Stelzer of European Molecular Biology Laboratory, is an advanced version of optical tweezers Equipped with an optional high-sensitivity quadrant photo detector (QPD), PFM is capable of trapping a micro object and monitoring the prompt and random Brownian fluctuations of the trapped object simultaneously. It exhibits a spatial resolution of a few nanometers to detect the relative position of the probe at an acquisition rate over 1 MHz. By capturing a flagella, we expect the rotation of the flagella could be detected. It is expected that the study of the swimming activity of P. aeruginosa provide potent method for the pathogenic role of the flagella in P. aeruginosa.