[5] Green sulfur bacteria are nonmotile (except Chloroherpeton thalassium, which may glide) and capable of anoxygenic photosynthesis.

[7] In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors.

[13] The majority of green sulfur bacteria are mesophilic, preferring moderate temperatures, and all live in aquatic environments.

[7] The Black Sea, an extremely anoxic environment, was found to house a large population of green sulfur bacteria at about 100 m depth.

The photosynthetic activity detected in the sulfide chemocline suggests that the bacteria need very little energy for cellular maintenance.

[14] A species of green sulfur bacteria has been found living near a black smoker off the coast of Mexico at a depth of 2,500 m in the Pacific Ocean.

Characteristics used to distinguish between these genera include some metabolic properties, pigments, cell morphology and absorption spectra.

The photosynthetic pigments in this genus are Bchl c, d or e. Some species require NaCl (sodium chloride) for growth.

The FMO complex helps efficiently transfer the energy absorbed by the antena to the reaction center.

Once the reaction center (RC) has given an electron to Fd it becomes an oxidizing agent (P840+) with a reduction potential of around +300 mV.

However, not all green sulfur bacteria produce this enzyme, demonstrating that it is not needed for the oxidation of sulfide.

These molecules are used as the raw materials to synthesize all the building blocks a cell needs to generate macromolecules.

The rTCA cycle is highly energy efficient enabling the bacteria to grow under low light conditions.

[9] Green sulfur bacteria are often referred to as obligate photoautotrophs as they cannot grow in the absence of light even if they are provided with organic matter.

[32] The bacterium uses electrons, generated from the oxidation of sulfur, and the energy it captures from light to run the rTCA.

C. tepidum also generates energy in the form of ATP using the proton motive force derived from sulfide oxidation.

[32] The majority of green sulfur bacteria are diazotrophs: they can reduce nitrogen to ammonia which is then used to synthesize amino acids.

[33] Nitrogen fixation among green sulfur bacteria is generally typical of an anoxygenic phototroph, and requires the presence of light.

Green sulfur bacteria exhibit activity from a Type-1 secretion system and a ferredoxin-NADP+ oxidoreductase to generate reduced iron, a trait that evolved to support nitrogen fixation.

[34] Like purple sulfur bacteria, they can regulate the activity of nitrogenase post-translationally in response to ammonia concentrations.

Their possession of nif genes, even though evolutionarily distinct, may suggest their nitrogen fixation abilities arose in two different events or through a shared very distant ancestor.

[33] Examples of green sulfur bacteria capable of nitrogen fixation include the genus Chlorobium and Pelodictyon, excluding P. phaeoclathratiforme.

Green sulfur bacteria living in coral reefs, such as Prosthecochloris, are crucial in generating available nitrogen in the already nutrient-limited environment.