Final answer:
To identify E. coli strains susceptible to Cipro using replica plating and indicator plates, researchers transfer bacteria from an initial agar plate to a Cipro-containing plate. Only Cipro-susceptible strains will fail to grow on the selective indicator plates, aiding in their identification.
Step-by-step explanation:
To test for strains of E. coli that are susceptible to the antibiotic Cipro using replica plating and indicator plates, researchers could start by growing a mixed culture of E. coli strains on an agar plate without the antibiotic. After incubation, a filter paper, often called a replica plate, is used to transfer bacteria from the original plate to a new plate containing Cipro. Only strains of E. coli susceptible to Cipro will fail to grow on this second indicator plate, thereby allowing identification of those strains.
Indicator plates with Cipro are selective media designed to prevent the growth of bacteria resistant to this antibiotic. If bacteria grow on these plates, they are likely to have resistance genes. In contrast, a lack of growth would suggest susceptibility to the antibiotic, enabling researchers to identify susceptible strains. An example of this method in action is the transformation experiment where E. coli bacteria mixed with a plasmid containing the gene for ampicillin resistance, with growth patterns indicative of antibiotic resistance properties.