FIG 1.

Monitoring of spheroplast formation by measuring the optical density at 600 nm (OD₆₀₀) during incubation of C. coli cultures at 37°C with S1 and S2 buffers containing various EDTA concentrations (12.5 to 100 mM). S2 buffer was added at a ratio of 1:1 immediately after 30 min of incubation with S1 buffer. L1 to L4, viable C. coli cells in exponential phase; D1 and D2, heat-inactivated (72°C for 10 min) C. coli cells.