Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

s, which are the primary pigments in plants, algae, and

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

. Organisms that contain bacteriochlorophyll conduct photosynthesis to sustain their energy requirements, but do not produce oxygen as a byproduct. They use wavelengths of light not absorbed by plants or

. Replacement of with protons gives bacteriophaeophytin (BPh), the phaeophytin form. BacterioChlorophyll a.svg, bacteriochlorophyll ''a'' BacterioChlorophyll b.svg, bacteriochlorophyll ''b'' BacterioChlorophyll c.svg, bacteriochlorophyll ''c'' BacterioChlorophyll d.svg, bacteriochlorophyll ''d'' BacterioChlorophyll e.svg, bacteriochlorophyll ''e'' Bacteriochlorophyll f.svg, bacteriochlorophyll ''f'' BacterioChlorophyll g.svg, bacteriochlorophyll ''g''

Structure

Bacteriochlorophylls ''a'', ''b'', and ''g'' are

bacteriochlorin In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins. The parent chlorin is an unstable compound which undergoes air oxidation to porphine. The name chlorin derives from chlorophyll. Chlorophylls a ...

s, meaning their molecules have a bacteriochlorin macrocycle ring with two reduced

pyrrole Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4 H4 NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-meth ...

rings (B and D). Bacteriochlorophylls ''c'', ''d'', ''e'', and ''f'' are chlorins, meaning their molecules have a chlorin macrocycle ring with one reduced pyrrole ring (D). Bacteriochlorophylls ''c'' to ''f'' occur in the form of closely related homologs with different alkyl groups attached to pyrrole rings B and C and are illustrated above in their simplest versions, esterified with the sesquiterpene alcohol

farnesol Farnesol is a natural 15-carbon organic compound which is an acyclic sesquiterpene alcohol. Under standard conditions, it is a colorless liquid. It is hydrophobic, and thus insoluble in water, but miscible with oils. Farnesol is produced from 5- ...

. Bacteriochlorophyll ''g'' has a vinyl group in ring (A).

Biosynthesis

There are a large number of known bacteriochlorophylls but all have features in common since the biosynthetic pathway involves chlorophyllide ''a'' as an intermediate. Isobacteriochlorins, in contrast, are biosynthesised from uroporphyrinogen III in a separate pathway that leads, for example, to siroheme, cofactor F₄₃₀ and cobalamin.

References

{{photolithotrophic bacteria Photosynthetic pigments Tetrapyrroles de:Chlorophylle#Chemische Struktur bei anoxygenen Phototrophen: Bakteriochlorophylle (Bchl)