Microscopic verification of purification procedure 1-C2-S2-H1-F2 at 400× magnification. A-C) Microscopic image of UASS-1 reactor. D-F) Microscopic image of UASS-2 reactor at different times of sampling. Images A and D represents samples before purification procedure, images B and E represent samples after purification procedure whereas images C and F show residues on the filter. All samples were diluted 500-fold. Cells were stained with DAPI. Microscopic images were generated using a Nikon Optiphot-2 microscope (Nikon, Duesseldorf, Germany) and a DAPI AMCA filter tube. Scale bar equals 50 μm.