Fig. 6.

Growth-phase-dependent regulation of P_guaB. A wild-type strain or a strain containing the fis : : aadA allele (Δfis), each harbouring a fusion of P_guaB (−69 to +36) to lacZ, were inoculated from a dense culture into fresh growth medium [M9 minimal medium containing 0.4 % (w/v) glucose, 0.8 % (w/v) Casamino acids and 5 μg thiamine ml⁻¹] to an OD₆₀₀ of ∼0.01. Samples were taken during different stages of growth and the β-galactosidase activity was determined. The promoter activity of the wild-type strain (•) and Δfis strain (○) is given in Miller units (β-galactosidase activity). Values presented are the mean±sd, for three independent experiments. Cell density measurements (OD₆₀₀) for single cultures that are representative of the growth curve for the wild-type strain (⧫) and the Δfis strain (□), were plotted on a logarithmic axis.