Cyanophyceae

Cyanophyceae, commonly known as blue-green algae, are a division of photosynthetic bacteria. Despite their common name, they are not true algae, which are eukaryotes. Cyanophyceae belong to the domain Bacteria and are characterized by their prokaryotic cell structure, lacking a defined nucleus and other membrane-bound organelles. Their pigmentation includes chlorophyll a and phycobilins, the latter being responsible for their characteristic blue and green colors, although other pigments can lead to red, brown, or black appearances.

These organisms are found in a wide range of environments, from marine and freshwater habitats to terrestrial soils and rocks, and even in extreme conditions like hot springs and Antarctic deserts. Cyanophyceae play crucial roles in ecosystems. They are primary producers, forming the base of many aquatic food webs. Some species have the ability to fix atmospheric nitrogen, a vital process that enriches soils and water bodies with essential nutrients. However, under certain conditions, such as high nutrient loads in water, some Cyanophyceae can undergo rapid proliferation, leading to harmful algal blooms that can produce toxins detrimental to aquatic life and human health.

Reproduction in Cyanophyceae is primarily asexual, occurring through cell division, fragmentation of filaments, or the formation of specialized spores like akinetes and endospores. Their evolutionary history is significant, with fossil evidence suggesting they were among the earliest life forms on Earth and played a key role in producing the oxygen in our atmosphere through photosynthesis.