Growth and genome-wide transcriptional effects of sulfur starvation. A. Growth curves. S starvation, with or without HEPES buffering, was initiated at mid-exponential phase (designated as time 0). A normal growth control culture was examined in parallel. B. and C. Representative ratio-intensity plots showing the dispersion of transcript abundance ratios 6 hr (B) and 72 hr (C) after sulfate removal. D. A representative ratio-intensity plot for salt stress experiments which was conducted as described [see Additional file 1]. R: F635median intensity ("experiment"); G: F532median intensity ("control"). The fluorescence intensity data were pre-processed as described in Methods.