Blue-green algae are actually a type of bacteria that is known as cyanobacteria. In their aquatic habitat, cyanobacteria are equipped to use the sun's energy to manufacture their own food through photosynthesis. The moniker blue-green algae came about because of the color, which was a by-product of the photosynthetic activity of the microbes, and their discovery as a algal-like scum on the surface of ponds. They were assumed to be algae until their identity as bacteria was determined.

Although the recognition of the bacterial nature of the microbe occurred recently, cyanobacteria are ancient. Fossils of cyanobacteria have been found that date back 3.5 billion years and are among the oldest fossils of any life from thus far discovered on Earth. These microorganisms must have developed very early following the establishment of land on Earth, because the oldest known rocks are only slightly older at 3.8 billion years.

Modern...