Humans can engineer microorganisms to synthesize useful chemicals. For example, humans have engineered bacteria to make erythromycin A, an antibiotic commonly used to treat infections. Erythromycin A is naturally made by the bacterium Saccharopolyspora erythraea. However, S. erythraea bacteria are slow-growing and difficult to manipulate in the laboratory. So, scientists copied the S. erythraea genes necessary for erythromycin A synthesis, and moved them into the common laboratory bacterium Escherichia coli. To do this, the scientists first extracted DNA from S. erythraea cells, and then amplified the erythromycin A synthesis genes. The scientists then used the amplified DNA to make recombinant plasmids containing the genes’ sequences. They introduced the plasmids into E. coli cells, and then cultured the cells. Finally, they used chromatography to confirm that the E. coli cells now produced erythromycin A. Which of the following techniques could the scientists have used to introduce the recombinant plasmids into E. coli cells? *
A). DNA extraction
B).DNA sequencing
C).Polymerase chain reaction (PCR)
D),Bacterial transformation