Fig. 5.

The effect of growth on algae and algal products directly and indirectly on IR1. (A) The effect of exposing IR1 to volatiles from the algae P. yezoensis and H. fusiforme. An ASWLow plate (assay plate) was inoculated in the center with a $10\mu \mathrm{l}$ aliquot containing ${10}^7$ cfu of WT IR1. This was placed facing a second plate (donor plate) containing salt agar without algae or with $10\mathrm{g}$ of the specified hydrated algae (either autoclaved or not). Plates were sealed with parafilm and incubated for 7 d under humidified conditions. (B) Example of fucoidan-triggered recovery of structural color. The entire 9-cm diameter agar plate was spread with IR1, which became intensely green across the whole plate after 24 h and then lost coloration completely after 7 d. Addition of $50\mathrm{mg}$ of powdered fucoidan to the center of the plate facilitated recovery of structural color after 1 d, as shown. (C) WT IR1 shown growing as a 6-mm diameter iridescent green colony on a $4\times 4$-${\mathrm{cm}}^2$ stack of P. yezoensis after $18\mathrm{h}$ at $20{}^{\circ }\mathrm{C}$. The algae were embedded in agarose with $1\%$ (wt/vol) KCl and nigrosin. (D) Culture of WT and IR1 mutants on 4-mm diameter stalks of H. fusiforme after $36\mathrm{h}$. (Scale bars in D, Left to Right, 1.5 mm.)