A. Facilitation of Fn biofilm formation by amyloid-like FadA. An aliquot of 10 μg each of the detergent-resistant pellets prepared from of Fn 12230 (wild type), US1 (∆fadA) and lam, or PBS, was added to the 96-well plates and incubated at 370C for 5 hours. Fresh culture of Fn 12230 was diluted to OD600 of 0.2 and an aliquot of 200 μl was added to the wells, followed by incubation at 37 0C for 48 or 72 hours under anaerobic conditions. Following washes, the biofilms were incubated with 100 μl 0.1% crystal violet for 15 min. After washing, 100 μl 95% ethanol was added to each well and the optical density at OD550 was measured in a microplate reader. The results shown are the average of four experiments each performed in duplicate. The error bars indicate SD. A representative image following 72 hours of incubation is shown in the top panel. ** p<0.01. ***p<0.001 (t-test). 