Fig. 2. Production of novel 1 congeners with modified catechol moieties. P. fluorescens WT and ΔobaL cultures were grown ± 2,3-dihydroxybenzoic acid (2,3-DHBA, 0.2 mM), 2-hydroxybenzoic acid (2-HBA, 0.4 mM), 3-hydroxybenzoic acid (3-HBA, 0.4 mM) and benzoic acid (BA, 0.4 mM). Representative HPLC chromatograms at 270 nm of extracts taken after 14 h of growth are shown, with photographs of aliquots from the cultures. As shown previously,²⁴ 2,3-DHBA restores 1 production to P. fluorescens ΔobaL, along with the characteristic purple colour. The retention time of 1 is indicated with a red dashed line. Peaks corresponding to novel 1 congeners are marked with a blue asterisk, with the numbers corresponding to Fig. 1. The peaks eluting between 7 and 8 minutes include the shunt metabolites 4-nitrophenylethanol and 4-nitrophenylacetate. For 2 and 4 the hydrolysed equivalents were also observed and are marked with a green asterisk. At least three biological replicates were carried out for each condition.