Competence-Induced DNA Uptake in Staphylococcus aureus

Take an S. aureus culture sensitive to the antibiotic chloramphenicol.

Centrifuge to pellet the bacteria and remove the supernatant.

Transfer the pellet to a tube containing nutrient-limiting media and incubate. Nutrient stress enhances competence-the bacterium’s ability to internalize foreign DNA.

Centrifuge again and remove the supernatant. Resuspend the pellet in fresh nutrient-limiting media.

Next, add DNA extracted from an S. aureus strain carrying a chloramphenicol-resistant gene. Incubate.

The DNA-uptake machinery processes the DNA into a single strand and translocates it to the cytoplasm, where it integrates into the bacterial chromosome.

Centrifuge and remove the supernatant. Resuspend the pellet in nutrient-rich media.

Transfer the suspension into molten nutrient-rich agar containing chloramphenicol.

Pour the mixture into a dish and incubate.

The growth of chloramphenicol-resistant colonies indicates successful DNA uptake.

Culture the recipient cell overnight, in five milliliters of TSB at 37 degrees celsius with shaking. The following morning, transfer 0.5 milliliters of the overnight culture into a 1.5 milliliter tube.

Precipitate the cells by centrifugation. Then suspend the cell