Question

Think of an experiment to perform if you continue to obtain more than one morphology in your phage preparations (e.g., some plaques are large and clear, and some are much smaller and cloudy). How would you determine that an individual phage yielded two different morphologies? What would be a possible mechanism by which one phage could yield two different morphologies? In one to two sentences, describe how each of the following might look: a. Doing a titer procedure and forgetting to add the bacteria b. Contaminated bacteria c. PB contaminated with phage d. PB contaminated with bacteria or fungus e. Doing a spot test and forgetting to add the top agar f. Using top agar that is not completely melted

Answer 1

Ans 16) In this if there is more than one morphology obtained in the phage preparation, an experiment which can help is streaking experiment with selective media. In the streaking technique, it helps in isolating the pure strain from species and hence it produces colonies from that species that is easy to identify. In order to determine that an individual phage yielded 2 different morphologies, it can be observed through the size and pattern of the colony formation. One possible mechanism using which one phage could yield two different morphologies is through dilution method and followed by streaking.

Ans 17)

1. In this the phage will look completely clear as no bacteria has been added to the same
2. In case of the contaminated bacterial colonies, the colonies will be differently colored and have morphological difference
3. The phage can be visualized with naked eyes and hence it will appear in different forms and color on the plate
4. If the PB is contaminated with fungus or bacteria, the solution becomes cloudy and yellow in color
5. On forgetting to add Top agar to spot less, middle of the plate will see a large spot
6. If the Top agar is not melted properly the plate will have spots from the particles of TA that could not melt properly