Cyanobacteria Microscopy Protocols

For light microscopy cyanobacteria were fixed in 1% glutaraldehyde (Sigma-Aldrich, Darmstadt, Germany) at 4 °C overnight. Subsequently, cells were washed three times with PBS and were analyzed with the inverse Nikon microscope Eclipse Ti-E (Nikon, Tokyo, Japan) as previously described [33 (link)]. For scanning electron microscopy (SAM) with the Zeiss Merlin field emission scanning electron microscope (Carl Zeiss, Oberkochen, Germany) cyanobacteria were fixed in the cultivation medium with glutaraldehyde (final concentration 2%). The final fixation was achieved after 30 min by adding formaldehyde (Riedel-de Haën, Seelze, Germany) to a final concentration of 5%. SAM was performed as previously described [33 (link)].