Is the statement true or false? A halo around bacterial growth on a starch plate after the addition of iodine indicates hydrolysis of starch.

The statement is true. A halo around bacterial growth on a starch plate after adding iodine indicates that the starch in the medium has been hydrolyzed, or broken down, by the bacteria.

When starch is present in the growth medium, it can be utilized by certain bacteria that possess the enzyme amylase. This enzyme breaks down starch into smaller sugar units. After incubation, when iodine is added to the plate, it reacts with the intact starch and produces a blue-black color. However, in areas where starch has been hydrolyzed due to bacterial activity, a clear zone will appear around the bacterial growth, indicating the absence of starch where the hydrolysis occurred. This phenomenon is a common method used in microbiology to identify amylase-producing bacteria.

The clarity of the halo is crucial because a distinct clear area confirms that starch breakdown has indeed taken place, validating the original statement regarding hydrolysis. This specificity of response to iodine color change underlines the biochemical activity of the bacteria concerning starch utilization.