Anoxygenic photosynthesis

Anoxygenic photosynthesis is a special form of photosynthesis used by some bacteria and archaea, which differs from the better known oxygenic photosynthesis in plants in the reductant used (e.g. hydrogen sulfide instead of water) and the byproduct generated (e.g. elemental sulfur instead of molecular oxygen). Several groups of bacteria can conduct anoxygenic photosynthesis: green sulfur bacteria (GSB), red and green filamentous phototrophs (FAPs e.g. Chloroflexia), purple bacteria, acidobacteriota, and heliobacteria. Some archaea (e.g. Halobacterium) capture light energy for metabolic function and are thus phototrophic but none are known to "fix" carbon (i.e. be photosynthetic). Instead of a chlorophyll-type receptor and electron transport chain, proteins such as halorhodopsin capture light energy with the aid of diterpenes to move ions against a gradient and produce ATP via chemiosmosis in the manner of mitochondria. The photopigments used to carry out anaerobic photosynthesis are similar to chlorophyll but differ in molecular detail and peak wavelength of light absorbed. Bacteriochlorophylls a through g absorb electromagnetic radiation maximally in the near-infrared within their natural membrane milieu. This differs from chlorophyll a, the predominant plant and cyanobacteria pigment, which has peak absorption wavelength approximately 100 nanometers shorter (in the red portion of the visible spectrum). There are two main types of anaerobic photosynthetic electron transport chains in bacteria. The type I reaction centers are found in GSB, Chloracidobacterium, and Heliobacteria, while the type II reaction centers are found in FAPs and purple bacteria. The electron transport chain of green sulfur bacteria — such as is present in the model organism Chlorobaculum tepidum — uses the reaction center bacteriochlorophyll pair, P840. When light is absorbed by the reaction center, P840 enters an excited state with a large negative reduction potential, and so readily donates the electron to bacteriochlorophyll 663, which passes it on down an electron transport chain.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related concepts (18)

Related courses (4)

Related lectures (65)

Related MOOCs (1)

Light-harvesting complex

A light-harvesting complex consists of a number of chromophores which are complex subunit proteins that may be part of a larger super complex of a photosystem, the functional unit in photosynthesis. It is used by plants and photosynthetic bacteria to collect more of the incoming light than would be captured by the photosynthetic reaction center alone. The light which is captured by the chromophores is capable of exciting molecules from their ground state to a higher energy state, known as the excited state.

Anoxygenic photosynthesis

Purple sulfur bacteria

The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments including hot springs, stagnant water bodies, as well as microbial mats in intertidal zones. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen.

ENV-202: Microbiology for engineers

"Microbiology for engineers" covers the main microbial processes that take place in the environment and in treatment systems. It presents elemental cycles that are catalyzed by microorganisms and that

CH-442: Photochemistry I

This course presents the theoretical bases of electronic spectroscopy and molecular photophysics. The principles of the reactivity of excited states of molecules and solids under irradiation are detai

CH-313: Chemical biology

Closely interfacing with bioengineering and medicine, this course provides foundational concepts in applying small-molecule chemical toolsets to probe the functions of living systems at the mechanisti

Water quality and the biogeochemical engine

Learn about how the quality of water is a direct result of complex bio-geo-chemical interactions, and about how to use these processes to mitigate water quality issues.

Explores biological and molecular catalysts for oxygen evolution, focusing on photosystem II, O-O bond formation, and ruthenium complexes.

Provides an overview of photosynthesis, including its evolution and the characteristics of different phototrophs.

Explores current-voltage measurements to confirm photosynthetically derived electrons in optical devices.