Figure 4.

Complementation using the marker-less approach. (A) Transformed mycoplasma cells were grown without any antibiotic selection in liquid culture through three serial passages with the dilution levels and culture durations indicated. After a new culture was started, the previous culture was stored at 4°C. (B) After the fourth culture, cells from each of the four successive cultures were diluted and plated on agar medium (also not containing any antibiotic) with X-gal to visualize the colonies. The enrichment of fast-growing colonies in later cultures suggests that the transformed and complemented cells overtook the population during later cultures.