Final answer:
Prototrophs are bacteria that can grow on minimal medium as they are wild type and have all the necessary genetic information to synthesize essential growth compounds. Strains like E. coli which can grow with supplementation are studied for metabolic complementation and genetic regulation.
Step-by-step explanation:
Prototrophs are bacteria that can grow on minimal medium and are assumed to be wild type. They possess all the genetic information necessary to synthesize essential compounds for their growth. Unlike auxotrophs, which require specific additional nutrients to grow because they have lost the ability to synthesize those nutrients due to genetic mutations, prototrophs do not need such supplementation. A classic example of a study using prototrophic and auxotrophic strains involves Escherichia coli. When two complementary auxotrophic bacterial strains are cultured together and exhibit mutual support, they can provide each other with missing nutrients, which enables both to grow on minimal medium without supplements. This is a demonstration of metabolic complementation. Moreover, identification of auxotrophs in a bacterial population is often accomplished through a method called replica plating, which reveals which colonies are unable to grow without specific nutrients.
Hfr (High frequency of recombination) cells, which carry an integrated F plasmid within the chromosome can, during conjugation, transfer part of their chromosomal genes to a recipient F- cell through a mating bridge. This process enables genetic mapping of the donor strain's chromosome. Through methods such as these, researchers can decipher genetic pathways and interactions in bacteria.
Experimenters like Francois Jacob and Jacques Monod have used different mutants to learn more about bacterial metabolism and genetic regulation. They identified E. coli strains that were unable to grow on lactose due to specific genetic mutations, which contributed to the understanding of how bacteria regulate the use of different sugars.