Origin of Microbial Life and Photosynthesis Origin of Photosynthesis

Photosynthetic bacteria are a group of bacteria that contain light absorbing pigments..

Bacteriology 102 - Purple Non-Sulfur Photosynthetic Bacteria

The traditional "photosynthetic equation" many of us grew up with is as follows:

This equation is meant to represent the incorporation of carbon dioxide into cellular carbohydrates with the utilization of water as the source of reducing power (electron donor) and the consequent release of oxygen. This equation is more accurately given as follows:

The cyanobacteria are oxygenic (oxygen-producing) photosynthetic bacteria that possess this type of photosynthesis along with plants and algae. The use of carbon dioxide as the carbon source and an inorganic compound (water) as the source of reducing power is reflected in the terms autotroph and lithotroph (respectively) which are used for an organism performing this reaction. With light as the ultimate source of energy, the organism would also be termed a phototroph.

Genome Evolution of Photosynthetic Bacteria

An updated taxonomic arrangement according to and the 2nd Edition of may be added here. In these resources, the inclusion of purple non-sulfur photosynthetic bacteria in the Alphaproteobacteria and the Betaproteobacteria is discussed.

The preceding equation can be made more general by substituting "A" for the oxygen ("O") in the source of reducing power when it is realized that compounds other than water can serve in that capacity for certain other types of organisms:

For the purple and green sulfur bacteria, hydrogen sulfide is utilized, and the equation is given thus:

Photosynthetic reaction center of green sulfur bacteria ..

Originally it was thought that these bacteria could not use hydrogen sulfide as an electron donor for the reduction of carbon dioxide when growing photoautotrophically, hence the use of "non-sulfur" in their group name. Sulfide can be used if present in a low concentration. Higher concentrations of H2S (in which the purple and green sulfur bacteria can thrive) are toxic, however. There is more about sulfide and sources of reducing power in section II, below.

Photosynthetic Bacteria – What Are Bacteria?

Allphotosynthetic organisms--with the exception of a minor group ofbacteria, the halobacteria--contain the light-absorbing pigmentchlorophyll, which plays a key role in the transfer of energy fromlight to chemical compounds.Photosynthesis is the fundamental process that maintains life onEarth.


There are two main types of photosynthesis: (the kind that generates O2) and (the kind that doesn’t generate O2). Anoxygenic photosynthesis is used mainly by the purple bacteria, the green sulfur and nonsulfur bacteria, the heliobacteria and the acidobacteria. Oxygenic photosynthesis is used by the cyanobacteria, the algae, and by plants.

Photosynthetic Organisms - Plants, Algae, Cyanobacteria

The Purple Non-Sulfur Photosynthetic Bacteria constitute a non-taxonomic group of versatile organisms in which most can grow as photoheterotrophs, photoautotrophs or chemoheterotrophs – switching from one mode to another depending on conditions available, especially the following: degree of anaerobiosis, availability of carbon source (CO2 for autotrophic growth, organic compounds for heterotrophic growth), and availability of light (needed for phototrophic growth).

07/10/2016 · What are Chemosynthetic Bacteria

Oxygenic photosynthesis occurs in, among others, eukaryotic microorganisms like algae and in bacteria such as cyanobacteria; the same mechanism is at work in both. Electron flow happens through two different electron transport chains that are connected; together, these electron transport chains are called the . The stars of each chain are photosystem I (PSI) and photosystem II (PSII), each containing chlorophyll reaction centers surrounded by antenna pigments.