Final answer:
Auxotrophs are bacterial mutants that cannot synthesize a specific nutrient due to a mutation, while prototrophs are wild-type strains that can synthesize all necessary nutrients. Replica plating is a technique used to distinguish between the two types by growing the bacteria on different types of media.
Step-by-step explanation:
An auxotroph is a type of bacterial mutant that is unable to synthesize a specific nutrient, such as an amino acid, due to a mutation in a gene encoding an enzyme in the biosynthesis pathway of that nutrient. In contrast, a prototroph is a wild-type bacterial strain that is able to synthesize all the necessary nutrients for growth on a minimal medium.
For example, let's consider histidine auxotrophs. These mutants are unable to synthesize histidine and therefore cannot grow on a medium lacking histidine. However, they can grow on a nutritionally complete medium that contains histidine. On the other hand, prototrophs can grow on both types of media.
The difference between auxotrophs and prototrophs can be identified using a technique called replica plating. This involves plating bacterial cells on both a nutritionally complete plate and a plate lacking a specific nutrient. Auxotrophs will only grow on the complete plate, while prototrophs will grow on both plates.