(A) Diluted sludge sample containing bacterial cells was inoculated on top of a 0.2 μm polycarbonate (PC) filter membrane sitting over the 0.02 μm filter of the Tissue Culture Insert (TCI). Nonsterile sludge medium held inside the TCI diffused to the bacterial cells. The entire apparatus was kept inside a tissue culture well.
(B) And (C) Micrographs of 2-week old culture showing bacterial cells labeled with a TM7 specific probe (orange-red) using FISH technique. Cells formed microcolonies on the PC filter. YOPRO-1, a DNA-binding dye, was used to label all cells (green). Notice that the TM7 microcolonies (orange-red) are mixed with other non-TM7 cells (green). Scale bars = 20 μm.