Final answer:
In the presence of lactose and X-gal during the lag phase, bacteria with a functional lac operon will produce β-galactosidase, an enzyme necessary for lactose metabolism. This can result in a color change if X-gal is present in the media.
Step-by-step explanation:
During the lag phase of bacterial growth in a lactose media, bacteria synthesize proteins needed for their growth within the medium. If the media also contains X-gal, a chemical similar to lactose, bacteria with a functional lac operon will produce an enzyme that metabolizes X-gal, leading to a visible color change in the colonies. In a condition where only lactose is present as a source of carbon, bacteria need to produce lactose-digesting proteins such as β-galactosidase, facilitated by the lac operon. The lacZ gene of the operon encodes for β-galactosidase, which is crucial in the utilization of lactose. In the presence of lactose, the lac repressor is released, allowing the transcription of the operon's genes, which results in the synthesis of the necessary enzymes for lactose metabolism.