Fig. 1.

2,3-Dihydroxybenzoate (DHB) is essential for biofilm formation. a A diagram of biosynthetic gene clusters for three different non-ribosomal peptides (NRPs) in B. subtilis. b Formation of pellicle biofilms by the mutants deficient in the biosynthesis of the three NRPs. Strains shown are WT(3610), Δpks(CY167), Δpps(CY168), and ΔdhbA(YQ90, insertional deletion). Cells were incubated in MSgg at 30 °C for 2 days before images were taken. Scale bar, 5 mm. c A 4-step enzymatic conversion from 3-chorismate to bacillibactin carried out by enzymes encoded in the dhbA-F operon²⁴. d Formation of pellicle biofilms by non-polar in-frame deletion mutants of the dhbA-F operon and chemical complementation. Strains shown are WT(3610), ΔdhbA(YQ97, in-frame deletion), ΔdhbB(YQ98), ΔdhbC(YQ99), ΔdhbE(YQ100), and ΔdhbF(YQ101). Cells were incubated in MSgg at 30 °C for 2 days before images were taken. For chemical complementation, DHB was added at the final concentration of 1 μg ml⁻¹ (~60 μM). Scale bar, 5 mm