The Collaborative International Dictionary
cyanobacterium \cyanobacterium\ pl. cyanobacteria \cyanobacteria\ [from the pigment phycocyanin.] any of a group of photosynthetic autotrophic prokaryotic microorganisms possessing characteristics of both bacteria and plants. When classed as bacteria, they are assigned to the Cyanobacteria; when classed as plants, they are assigned to the Cyanophyta. They were earlier named blue-green algae, a term less used now in technical discussions. Since the chlorophyll within the cyanobacteria is diffused throughout the cell, rather than being contained in chloroplasts, they are no longer thought of as true plants.
Wiktionary
n. (context biology English) Any of very many photosynthetic prokaryotic microorganisms, of phylum ''Cyanobacteria'', once known as blue-green algae.
Wikipedia
Cyanobacterium is a genus of cyanobacteria.
Usage examples of "cyanobacterium".
At some point in the first billion years of life, cyanobacteria, or blue-green algae, learned to tap into a freely available resource—the hydrogen that exists in spectacular abundance in water.
As they went through their chemical routines, the cyanobacteria became very slightly tacky, and that tackiness trapped microparticles of dust and sand, which became bound together to form slightly weird but solid structures—the stromatolites that were featured in the shallows of the poster on Victoria Bennett’s office wall.
Microbes, including the modern versions of cyanobacteria, supply the greater part of the planet’s breathable oxygen.
For one thing, cyanobacteria survived the experience, and they photosynthesize.
The average temperature was below the freezing point of water, and what little oxygen existed was mostly generated by cyanobacteria sharing the air with the clouds above—clouds trapped in warmer atmospheric layers and never yielding rain.
Apart from faint hints in the deep equatorial basins some of his fellow surveyors were exploring, the cyanobacteria in the clouds proved once and for all that such life could evolve independently on another world.
The Adrasteian cyanobacteria had never evolved into anything terribly sophisticated.
Three and a half billion years ago the cyanobacteria developed photosynthesis -- using the energy of sunlight to split water into hydrogen and oxygen.
The cyanobacteria kept the hydrogen and excreted the oxygen, polluting Earth's atmosphere with it (from the point of view of the other, anaerobic, bacterial.
So they'd put a landing craft smack in the center of the caldera to look for life -- and they'd found it: strange forms of cyanobacteria, eating CO2 and nitrogen, water and sunlight, and slowly replicating as they'd done for the past billion-odd years.
At some point in the first billion years of life, cyanobacteria, or blue-green algae, learned to tap into a freely available resource—.
The bioengineers were already working on new microorganisms: shifting, clipping and recombining genes from algae, methanogens, cyanobacteria, and lichens, trying to come up with organisms that would survive on the present Martian surface, or under it.