Sulfur Bacteria
Green & Purple Sulfur Bacteria
Features
Anaerobic bacteria
Thought to be the endosymbiont group for eukaryotes, and the origin of the mitochondria
Filamentous
Photosynthetic
Use bacteriochlorophyll a as well as bacteriochlorophylls c, d, or e
Use hydrogen sulfide gas, instead of water, during the reduction process
2H2S (sulfide) + CO2 ---> CH2O (sugar)+ S2 (sulfur) + H2O
Ecological Importance
Sulfur is abundant in nature, but plants can only use sulfate
Hydrogen sulfide (H2S) is toxic to aquatic flora and fauna
Sulfur anions (SO4+) can make inorganic salts, such as phosphorous, available to plants
Sulfate prevents excessive alkalinity from ammonia produced by microorganisms
Geologic Age
Paleoproterozoic - present
Additional Reading
Sulfur bacteria structurally unchanged in 1.8 billion years (PNAS 2014)
Origin of Bacteriochlorophyll a and the Early Diversification of Photosynthesis (PLOS One 2016)