Question

1. How does true motility differ from Brownian movement? 2. What could happen if you would touch the bottom of the motility agar with your needle during inoculation? 3 Explain why the following steps are essential during subculturing: a) Flaming the loop or needle prior to and after each inoculation. b) Cooling the loop or needle prior to obtaining the microorganism c) Holding the test tube caps in the hand as opposed placing them on the bench top. d) Flaming the neck of the tubes immediately after uncapping and before recapping. 4 How can you ascertain whether a culture grown on an agar slant is contaminated? 5 How could you explain if a four-quadrant streak plate culture shows more growth in quadrant IV than in quadrant III?

Answer 1

1. True motility is the movement of molecules in a particular path or consistent direction. Molecules may be twisting and turning along the path.While, in browninan movement molecules of a suspending liquid collide with the organism. the movemnt is jerky or irregular or the cells appear to be vibrating.

Also, in true motility cells show independent movement as compared to in brownian movement.

2. if needle touches the bottom it will puncture the agar.hence, the growth of colonies will be hard to detect.

3.a) flaming the loop prior to each inoculation is essential in oreder to sterilize the loop so that there is no other contamination other than your inoculum/sample. flaming the loop after each inoculation helps sterilize any left over sample so that the next sample is not contaminated with the previous sample.

b)Cooling is done in order to avoid killing the inoculum.

c)there is a higher chance of contaminants being present on the bench top as compared to the hand, since gloves are worn and sterilized by alcohol prior to the experiment.hence, it is advised not to place test tube caps on benchtop.

d)Flaming is done to eliminate any chance of contaminants entering the tube. flaming kills any micoroganism on the lip of the tube.

4.if there is a fungal contamination it appears as a fuzzy, filamentous hair like growth.if there is a bacterial contamination in a bacterial culture,there will be a difference in morphology.