Figure 4. Nutrient availability influences transcription of L. monocytogenes metabolic and virulence genes.

A. Transcription levels of key metabolic genes during growth of WT L. monocytogenes in BHI medium, minimal defined medium (MDM) and MDM with low concentrations (10-fold less) of BCAAs, histidine (His), arginine (Arg) and adenine (Ade). Transcriptional levels are presented as relative quantity (RQ), relative to BHI medium. B. Transcription levels of prfA, hly, and actA virulence genes during growth of WT L. monocytogenes in BHI medium, MDM, MDM with low concentrations of BCAAs, His, Arg and Ade and in MDM with low concentrations of phenylalanine (Phe) and tryptophan (Trp) (10 µg ml⁻¹). Transcriptional levels are presented as RQ, relative to BHI medium. C. Transcription levels of prfA, hly, and actA virulence genes during growth of WT L. monocytogenes in MDM and MDM with low concentrations of the designated nutrients. Transcriptional levels are presented as RQ, relative to MDM. D. Transcription levels of ilvC, hly, and actA genes during growth of WT L. monocytogenes in MDM and MDM with low concentrations of the designated nutrients. Transcriptional levels are presented as RQ, relative to MDM. Overnight precultures were grown in MDM media and diluted for growth under the indicated conditions. Bacteria were harvested at O.D._{600 nm} of 0.3, representing exponential growth. mRNA levels were normalized to rpoD mRNA. The results represent 3 independent experiments (N = 3). Error bars indicate a 95% confidence interval.