uPVC coupon covered with a mono and dual-species L. pneumophila biofilm. Microphotograph of an uPVC coupon visualized under EDIC microscopy covered with a 32 days-old biofilm formed by L. pneumophila (a) and L. pneumophila and Sphingomonas sp. (b). The black arrow indicates individual cells attached to the uPVC surface and white arrow indicates a microcolony. Bars represent 20 μm.