The mobility of Ps.fluroscens

Three patterns used in the experiment of E. coli, the plaza zone, the parallel tracks and the irregular blocks, have also been applied in the research of Ps. Fluroscens. As mentioned in introduction, the Ps. Fluroscens has a type of specific protein that enables the bacteria to present a bright green color under the UV lights. Then, it will be clearer to observing the Ps. Fluorescens under a dark background as all the figures present. Firstly, in the plaza zone, cells of Ps. Fluroscens in this area are generally in random movements as Figure 1 presented, and the trajectories of cell are similar to an irregular wave form. The average speed measured and calculated by the Image J due to the trajectories recorded is around the 14.01 um/s with an error of -6.57 um/s. The error is mainly resulted from the wave-liked routines of Ps. Fluroscens movements. Image J can only record and measure the projection distance of the wavy routines on the surface. So the vertical distance in microfluidics channel has not been involved in the calculations as the part of the movements of Ps. Fluroscens cells.

This phenomenon is also existed in the Ps. Fluroscens movements in parallel tracks. However, the measured mobility of bacteria in parallel tracks has not been influenced much by this phenomenon, since the channel is much narrower to the bacteria comparing to the plaza zone, and the Ps. Fluroscens cells have smaller free space to vary the directions. Velocities of bacteria in track six, seven and eight have been calculated. The speed of bacteria in these three tracks are in a range from 10 um/s to 29.14 um/s and the average speed is about 24.975 um/s. From the observation, the lowest speed of the bacterium can mainly be explained as the trajectory in microfluidics is going deeper inside of the channel rather than going forward as Figure 2 and 3 shows. As the Image J can only measure the displacement projected on the surface, the measured length of trace is smaller than the actual length, and the speed in calculation is smaller in consequence as well.

Figure 1 Trajectories in plaza zone

Figure 2 Ps. fluroscens enter the tracks first

Figure 3 Ps. Fluroscens going deeper in the tracks

Irregular block

Since the pseudomonas fluorescens can produce fluorescence when they are exposed by UV light, the observation of the mobility of pseudomonas fluorescens in the irregular block area become intuitionistic to see. It can be seen that the movement of them varied significantly from that of E. coli. Pseudomonas fluorescens did not resemble E. coli which preferred to swim straight in the microchannels or even turn at smaller angles. The majority of pseudomonas fluorescens just tended to stick together and remained their location with only small swing of their body. This phenomenon was generated by one of characteristics of ps. Fluorescens, which is the flagella of them prefers to adhere to the wall or other place for a long time. In that case, bacteria are not capable to leave although they dislike being stable. Hence, some bacteria who struggled to be free just could rotate themselves with fixed flagella. The figure 4 shows that two pseudomonas fluorescens were stable to keep their location in parallel at initial time and then one of bacteria spun to change its orientation. This phenomenon also indicated that some of them had the will to move in the microchannels. It can also be concluded that the bulk of them stayed at the corner of each irregular block without any shift in displacement and since the longtime of being irradiated by UV light, they became dim. The bacteria in the plaza-like space which is separated by the irregular block could be divided in several groups rather than distributed anywhere (figure 5). All the observations demonstrated that pseudomonas fluorescens processed the property to stick to the substance and the probability of moving was lower than others.

Figure 4 Ps. fluroscens stick together

Figure 5 Ps.fluroscens in groups