Hello, see attached paper about search for non photosynthetic cyanobacteria.

Good luck!

Conversation this week on Tweeter:

https://twitter.com/PatSchloss/status/1102695978719723521

Mostly on human guts but it's likely to be a biased observation due to the high sampling effort in comparison with any other environments.

The paper on the discovery of cyanos at the continental shelf is an excellent example of some of the ecological constraints to consider for where you may find similar organisms.

Basically, that paper shows that rock-dwelling cyanos that were extremely tolerant to nutrient stress developed new strategies to thrive in the absence of light. This provides probably the most important ecological variable to consider in your search which is looking at low light/no light environments.

In addition, mixotrophic lineages are also important to consider. This lifestyle is widespread in the environment and often offers a competitive advantage in times of nutrient stress, particularly for nutrients such as organic carbon, phosphorus, iron and trace elements. In such cases, it is not uncommon for photosynthetic bacteria to do away with a functional photosynthetic protein complex if harvesting light is really not working.

If we're focusing purely on autotrophs reducing CO2 into biomass, you will also want to look at environments where there are strong enough electron donors to fuel this reducing-power intensive process. Some that come to mind are hydrogen, and sulphide to start.

On a similar note, you'll want to look at environments that support fermentation via the availability of small organic acids and perhaps provide enough terminal electron acceptors to support anaerobic respiration. If the cells are not receiving enough light to drive oxygen production by splitting the H2O molecule, they will need to find other means of generating energy chemotrophically.

I know this doesn't exactly help narrow it down but I hope it gives you some inspiration about thinking why cyanos may have lost photosynthetic function. Basically you're looking for a dark environment, with relatively more reduced sources of electron and potentially, a variety of other metabolites that can support chemotrophic metabolism. I think the real challenge will be teasing this signal apart from the chemotrophic community that is already there. The paper recommended in the twitter conversation by Xabier Vázquez Campos is an excellent starting point.

Happy hunting!

And here is the paper by https://www.researchgate.net/profile/Fernando_Puente-Sanchez and colleagues for your convenience:

Article Viable cyanobacteria in the deep continental subsurface

There are other cyanobacteria in symbiosis with algae that lost photosynthesis. Look for UCYN-A and the spheroid bodies of Rhopalodia gibba.

I'm getting some great answers here guys, thanks! I will in depth review the information you have suggested soon; but I also have a brief question as I am more computational -> are the non photosynthetic cyanobacteria diverse (genetically)?

Hi , I agree with the Daniel Gregoire answer

Thank you everyone this has been immensely helpful!