Prokaryotes

Cyanobacteria (blue-green algae)

Live in oxic environments

Evolve O2 during photosynthesis

Contain chlorophyll

Occur in fresh and salt water, moist soils

Unicellular or chains of cells

Most only grow in light

Many have a gliding motility

Eubacteria

Phototrophic

• do photosynthesis in anoxic environments
• do not evolve O2 during photosynthesis

Chemolithotrophic

• Get energy from oxidation
• Use reduced inorganic compounds as e donors
• Fix CO2

Chemoorganotrophic

• Get energy from oxydation-reduction reactions
• Use organic compounds as e donors

Archaebacteria

Methanogens

• Strictly anaerobic
• pH 6.5 to 7.5
• Produce CH4 and CO2
• Most can use H2 as an energy source
• Most use CO2 as a terminal e-acceptor
• Terminal steps of anaerobic recyling of organic matter

Halobacteria

• Live in concentrated salt solutions

Sulfolobus, Thermoplasma, and Desulfurococcus

• Live in hot environments