Fig. 5.
Long-term changes in CoSMO. (A) Stabilization of partner ratios. At time 0, duplicate CoSMO cultures (brown and blue) were initiated at OD600 of 0.01 (4.7 × 105 total cells per ml) and R→L←A:Y→A←L ratios of 103 (I), 1 (II), and 10−3 (III). When OD600 exceeded the set point of 0.06 for the first time, two 3-ml samples were taken from each culture (brown and magenta from the brown; blue and cyan from the blue), and thereafter diluted once per day (magenta and cyan) or twice per day (brown and blue) to the set point. A low set point was chosen so that nutrients other than adenine and lysine were not limiting. Plots show R→L←A:Y→A←L ratios over time, with triangles marking points of dilution. (B) Increased ability to survive reductions in population density. Five 2.6-ml CoSMO cultures, initiated at different partner ratios, were grown to near-saturation and used as Round-0 cultures for five independent series. After 10 rounds of dilution and regrowth in 2.6 ml, a near-saturation Round-10 culture was obtained for each series. Each row corresponds to a particular series and depicts the number of tubes (of three) that were viable at indicated dilutions for Round-0 (Left) and Round-10 (Right) cultures. Population densities of R→L←A (red) and Y→A←L (green) in million cells per ml for Round-0 and Round-10 cultures are shown in the Inset.