Cyanobacteria

Cyanobacteria, also known as Cyanobacteriota or Cyanophyta, constitute a phylum of photosynthetic prokaryotes capable of oxygenic photosynthesis. Their name derives from the Greek "kyanos" (blue), reflecting their characteristic blue-green hue. While commonly called blue-green algae, they are not true algae but gram-negative bacteria. These ancient microorganisms have played a crucial role in Earth's history, significantly influencing atmospheric composition and evolving into chloroplasts in plants.