Definition of "cyanobacterium" []

• A photosynthetic bacterium of the class Coccogoneae or Hormogoneae, generally blue-green in color and in some species capable of nitrogen fixation. Cyanobacteria were once thought to be algae. Also called blue-green alga. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Synechococcus is a genus of cyanobacterium which is distributed widely in the oceans, although there are also some freshwater species."
• "Here we see a sheath, and on the inside can see a chain of cells, rod-shaped cells, that make up the trichome of a cyanobacterium."
• "He also puts up an image of a cyanobacterium that appears to house a stack of dimes all just faintly connected."