I am working on a local isolate of Synechocystis sp.. A uni-algal culture has been successfully established. when a loopful of this culture is streaked on BG-11 plates, there were 3-4 types of bacterial colonies present on the plates along with the Synechocystis colonies, from this plate, Synechocystis colony was re-streaked onto fresh plate to further separate the microorganisms.

on this new plate, the cyanobacterial colonies appeared a few days late and were smaller than usual. When the separated Synechocystis colony was transferred into fresh plate or BG11 broth, there was no growth even after several weeks of incubation. My first thought was that there might be a symbiotic interaction between Synechocystis and bacteria, then I intentionally introduced a Bacillus sp. into the broth, the cyanobacterium grew well.

currently, the only way I know, to grow Synechocystis separately from associated bacteria, is to streak bacteria and Synechocystis alongside each other, as shown in the attached images.

I prepare BG-11 plates using washed agar (also tried agarose with similar results) supplemented with sodium thiosulphate.

I have tried vitamin supplementation, adding 0.22 µ filtered bacterial lysate.

If anyone has experience in situations like this, kindly help me out....