Figure 1.

Respiration suppresses wrinkling and matrix gene expression. (A) Colony wrinkling increases with decreasing oxygen concentration, except when nitrate is used as a terminal electron acceptor. The wild strain 3610 was grown on solid biofilm-inducing medium containing 250 μM iron chloride at the indicated oxygen concentrations for 4 d in an environmental chamber. The medium contained 20 mM KNO₃ for the colony grown on nitrate. (B,C) Matrix gene expression increases with decreasing oxygen concentration, except in the presence of nitrate. Gene expression was monitored using a P_tapA-lacZ-containing strain (RL4582) (B) and a P_tapA-yfp-containing strain (RL5477) (C). Colonies were grown in the environmental chamber for 48 h. For B, colonies were harvested in triplicate, and P_tapA-lacZ activity was measured. (MU) Miller units. For C, colonies were examined using a dissecting fluorescence microscope (Zeiss).