Figure 4

a: Levels of sigma factor mRNAs during nitrogen starvation. Cells were grown under normal (white columns) or nitrogen starved (grey columns) conditions. sig mRNAs were quantified using quantitative RT-PCR. Each sample was measured in triplicate and the standard deviation is indicated by error bars. Values were normalized to the rpoA transcript. The expression of each gene in non starved cells was set equal to 10 (in arbitrary units). b: Effect of sigma mutations on the transcription of glnN gene during nitrogen starvation. mRNAs were quantified using quantitative RT-PCR. Each sample was measured in triplicate and the standard deviation is indicated by error bars. Values were normalized to the rpoA transcript. The expression of glnN gene in non starved cells (white columns) was set equal to 10 (in arbitrary units). The grey bars represented the expression of glnN gene in nitrogen starved cells.