Lichen is essentially a symbiotic entity - a fungus and an algae living together. Cyanobacteria is included in this very broad family - it's blue-green algae. You want to avoid blue-green algaes; aside from anything else they have toxins that could lead to motor neurone disease (you *really* don't want to get that).
I mentioned before Icelandic Moss which I have and use in brewing; I looked up the algae that it has - from memory, it's a green algae. Icelandic Moss has been known for centuries as a food (maybe the Vikings were eating it!) Traditional cold remedy, apparently.
Wiki has an entertaining session on edible lichen, it mentions:
(
http://en.wikipedia.org/wiki/Lichen#Food)
Iceland moss (Cetraria islandica)
Wila (Bryoria fremontii)
Reindeer lichen (Cladina spp) (that's the Caribou lichen Schnecken mentions)
Rock tripe (Umbilicaria spp. and Lasalia spp.) (sounds tasty dunnit? Rocks and tripe, everyone loves eating 'em)
One issue that you would have to look into is how to isolate and grow an edible lichen. Not a common hobby as far as I know! Then you'd have to find a way to grow that lichen in a way that is not incompatible with cheese bacterial growth and maturation. (Sounds like the Caribou gut cheese people are onto that, maybe shoot them an email?)
You could also try doing it with moss! A bit less complicated than lichen in some ways I reckon; but similar issues - what if it's toxic?