Cyanobacteria << `sy` uh noh bak TIHR ee uh >>, sometimes called blue-green algae, are a single-celled type of life that uses energy from sunlight to make food. Most cyanobacteria can be seen only with a microscope. They generally live in water. Like other bacteria, these organisms (living things) each have a prokaryotic cell that lacks a nucleus. Cyanobacteria are sometimes called algae because they contain chlorophyll, a green pigment that occurs in true algae as well. In a process called photosynthesis, the chlorophyll uses energy from sunlight to make food. However, cyanobacteria are not closely related to true algae. True algae are not bacteria. Cyanobacteria may also contain blue or red pigments. The combination of pigments causes some to appear pinkish, brownish, or black.
Most species (kinds) of cyanobacteria reproduce only by cell division. They take nitrogen from the air and convert it to a compound called ammonium. Growing cyanobacteria use ammonium as a nitrogen source to help them reproduce. When cyanobacteria cells die, the nitrogen is then released to fertilize soil or water.
Some cyanobacteria form slippery, dark coatings on rocks along the shores of rivers, lakes, and oceans. Others occur in soil, forming a slimy layer on wet ground. Lakes with large numbers of cyanobacteria look greenish or bluish-green. A few species of cyanobacteria may poison fish, cattle, or other animals that consume water containing these organisms.
See also Algae.
