Your bacterium is growing on a type of medium called casein agar, which contains milk protein (casein). There is a clear zone around the growth area of the bacterium, showing that it is synthesizing the enzymes needed to catalyze the breakdown of casein. These enzymes are considered .

The correct answer is: Exozymes.

Explanation:

Enzymes can be defined as the biological molecules, which are mostly proteins, and are capable of increasing the speed of a biochemical reaction by lowering the activation energy barrier for the particular biochemical reaction.The enzymes are highly specific for the substrate molecules on which they act.Exozymes are those enzymes which are secreted from the cells from the interior to the external environment where they act on substrate molecules absent in the cell interior by present in the cell exterior.In the given question, a clear zone formed on the casein agar plate by the growth of the bacteria is due to the digestion of the casein protein by the particular exozyme (probably, rennin or chymosin) produced and secreted by the bacteria.