FIG 3.

Upregulation of genes in the C58 HCA regulon in the iron uptake category. (A) Ferulic acid degradations by the C58 strain at a low iron concentration. Ferulic acid degradations were performed with cells at an OD₆₀₀ of 1 in AT medium with 500 μM ferulic acid, with or without DIP (an iron chelator), as described in Materials and Methods. The amounts of ferulic acid and its intermediary compounds (HMPHP and vanillic acid) were monitored using HPLC with a UV-visible diode array detector set at 280 nm, 0 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, and 7 h postinoculation. Results presented are representative of at least three biological replicates. (B) The SpG8-3 region, spanning atu3663 to atu3691, encodes the biosynthesis of a siderophore. It is composed notably of two operons, beginning with atu3674 and atu3675 (24). Histograms represent fold changes in expression levels measured from cells cultivated in AT medium with succinate, with versus without ferulic acid (black bars) or with versus without p-coumaric acid (white bars). Each gene is represented by an arrow directed to the right for the gene transcribed from the plus strand and to the left for the gene transcribed from the minus strand. Gray arrows, genes with significant expression differences, according to ANOVA, at the 0.05 level.