cyanobacteria

Examples of cyanobacteria in the following topics:

• The Evolution of Plastids

  • Plastids may derive from cyanobacteria engulfed via endosymbiosis by early eukaryotes, giving cells the ability to conduct photosynthesis.
  • Like mitochondria, plastids appear to have a primary endosymbiotic origin, but differ in that they derive from cyanobacteria rather than alpha-proteobacteria.
  • Cyanobacteria are a group of photosynthetic bacteria with all the conventional structures of prokaryotes.
  • In addition to thylakoids, chloroplasts found in eukaryotes have a circular DNA chromosome and ribosomes similar to those of cyanobacteria.
  • (a) Red algae and (b) green algae (visualized by light microscopy) share similar DNA sequences with photosynthetic cyanobacteria.

• The Purpose and Process of Photosynthesis

  • Plants, algae, and a group of bacteria called cyanobacteria are the only organisms capable of performing photosynthesis.
  • Photoautotrophs, including (a) plants, (b) algae, and (c) cyanobacteria, synthesize their organic compounds via photosynthesis using sunlight as an energy source.
  • Cyanobacteria and planktonic algae can grow over enormous areas in water, at times completely covering the surface.

• Endosymbiosis and the Evolution of Eukaryotes

  • Mereschkowski was familiar with work by botanist Andreas Schimper, who had observed in 1883 that the division of chloroplasts in green plants closely resembled that of free-living cyanobacteria.
  • More detailed electron microscopic comparisons between cyanobacteria and chloroplasts combined with the discovery that plastids (organelles associated with photosynthesis) and mitochondria contain their own DNA led to a resurrection of the idea in the 1960s.
  • These cyanobacteria have become chloroplasts in modern plant cells.

• Symbiosis between Bacteria and Eukaryotes

  • Biological nitrogen fixation (BNF) is exclusively carried out by prokaryotes: soil bacteria, cyanobacteria, and Frankia spp.
  • Cyanobacteria are the most important nitrogen fixers in aquatic environments.

• The Nitrogen Cycle

  • Cyanobacteria live in most aquatic ecosystems where sunlight is present; they play a key role in nitrogen fixation.
  • Cyanobacteria are able to use inorganic sources of nitrogen to "fix" nitrogen.

• Genomics and Biofuels

  • Knowledge of the genomics of microorganisms is being used to find better ways to harness biofuels from algae and cyanobacteria.

• Mutualistic Relationships with Fungi and Fungivores

  • Fungi form mutualistic associations with many types of organisms, including cyanobacteria, plants, and animals.
  • Some cyanobacteria fix nitrogen from the atmosphere, contributing nitrogenous compounds to the association.

• The Importance of Seedless Vascular Plants

  • Because they establish symbiotic relationships with nitrogen-fixing cyanobacteria, mosses replenish the soil with nitrogen.
  • The water ferns of the genus Azolla harbor nitrogen-fixing cyanobacteria and restore this important nutrient to aquatic habitats.

• Energy and Nutrient Requirements for Prokaryotes

• Early Eukaryotes

  • Cyanobacteria used water as a hydrogen source and released O2 as a waste product.
  • Originally, oxygen-rich environments were probably localized around places where cyanobacteria were active, but by about 2 billion years ago, geological evidence shows that oxygen was building up to higher concentrations in the atmosphere.