FIG. 2.
Yeast-extract-mediated repression of mRNA expression from Pu (A) and PS1 (B) promoters in P. putida KT2440 (pWW0). Cells grown overnight in M9 minimal medium with glucose as the carbon source were diluted to an optical density at 660 nm of 0.2. When the cultures reached exponential growth, they were divided into four fractions, three of which were supplemented with o-xylene (o-xyl), 1% (wt/vol) yeast extract, or both. The fourth fraction was left unsupplemented as a control. Cultures were incubated at 30°C for 30 min, and samples were collected for primer extension mRNA analysis. cDNA bands corresponding to each promoter (134 nucleotides for Pu and 206 for PS1 [bottom]) were quantified and compared.