Figure 4.

The PC content of cho2opi3 cells in choline-deficient medium is halved with every doubling of the cells, until growth ceases at a PC content below 2% of total phospholipids. Mid-log cho2opi3 cells (OD₆₀₀ = 0.4) cultured in synthetic complete lactate medium containing 1 mM choline were harvested, washed, and used to inoculate fresh synthetic complete lactate medium with (right) or without 1 mM choline (left) to an OD₆₀₀ of 0.02 at time 0. At the indicated times, samples were analyzed for phospholipid composition by steady-state labeling with [³²P]orthophosphate as detailed in the experimental section. The contents of the four most abundant phospholipid classes are shown on a logarithmic scale (left y-axis) as percentages of the total label incorporated into glycerophospholipids and together account for >95% of the incorporated label. Growth rates (▵, dashed lines) were monitored in parallel by the OD₆₀₀ (right y-axis).