Quantitation of RpoS. Overnight bacterial cultures grown in LB were harvested, lysed and their total protein content resolved by SDS-PAGE. Proteins were immunoblotted with anti-RpoS monoclonal antibodies. The bands were scanned and quantified. Densitometric measurements were normalised against ECOR 56 to which was assigned 100 units. Relative values represent the mean ± S.E. of at least three independent experiments.