Question

You will also need to know about UV sensitivity. For example, explain what is going on with the plates pictured below? The organism was S. mar so it is pink when it grows at room temp fyi.

Answer 1

The bacteria S. mar grows on plates that have growth media into a pink lawn. The bacteria, however, when exposed to UV light undergoes mutation. If the exposure is high enough, the bacteria will not be able to divide and the cells would die.

Here, we can see that there are white patches of specific shape over those red lawns. This implies that only these specific areas were treated with UV exposure. The exposure was intense enough to kill the bacteria in the exposed patch.

This can be achieved by covering the plates by papers that have a shape cut. The UV cannot penetrate the paper and hence would kill the bacteria only at the cut spaces that are exposed. This gives the desired shapes as seen in the above plates.