Bacillus subtilis growing in culture. On the left, we see all the cells in a colony. On the right, we see only the cells in normal growth phase because these cells express a green fluorescent protein. After the normal exponential growth phase, there is a "diauxic shift" when growth slows and many of the cells sporulate. This image corresponds to supplemental movie 3 from PNAS 105(11), 4393-4398, 2008.
Microscope slide with live cells in media was incubated in a temperature-controlled Cube and Box incubation system (Life Imaging Services) automated microscope (Zeiss 200M) at 30°C. Images were obtained with a CoolSNAP HQ (Princeton Instruments) at a magnification of either 63X or 100X. Metamorph microscope control software (Universal Imaging) was used. Phase-contrast and fluorescent images were recorded every 5 min for the first 122 frames and every 12 min for the remainder of the time lapse. To prevent phototoxicity, the excitation light (480-520 nm for 2 s) was limited to 5% of the output of a 100-W Hg-vapor lamp by neutral density filters. Emission wavelengths were 505-565 nm (filters from Chroma).
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