FIG. 3.

Transcript levels of dnaA (top) and ftsZ (bottom) in the turbidostat culture of Prochlorococcus sp. strain PCC 9511. Light (8 a.m. to 8 p.m.) and dark (8 p.m. to 8 a.m.) phases are shown by the black and white bars, respectively. Samples were taken at 4-h intervals. The RNA levels were determined by Northern hybridization (dnaA) or RNase protection assays (ftsZ). The size of the undigested ftsZ RNA probe was 621 nt, and that of the full-length ftsZ protected fragment was 571 nt. A DNA probe for rnpB was used to assess the amounts of RNA loaded per lane.