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Chloroflexus aurantiacus

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Title: Chloroflexus aurantiacus  
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Subject: Extremophile, Phototrophic bacteria, Xerophile, Chlorosome, Pyrococcus furiosus
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Chloroflexus aurantiacus

Chloroflexus aurantiacus
Scientific classification
Kingdom: Bacteria
Division: Chloroflexi
Class: Chloroflexi
Order: Chloroflexales
Family: Chloroflexaceae
Genus: Chloroflexus
Species: C. aurantiacus
Binomial name
Chloroflexus aurantiacus
Thermophilic Organisms

Chloroflexus aurantiacus is a thermophilic and can grow at temperatures from 35 °C to 70 °C. Chloroflexus aurantiacus can survive in the dark if oxygen is available. When grown in the dark, Chloroflexus aurantiacus has a dark orange color. When grown in sunlight it is dark green. The individual bacteria tend to form filamentous colonies enclosed in sheaths, which are known as trichomes.


  • Physiology 1
  • Evolution of photosynthesis 2
    • The "respiration early" hypothesis 2.1
  • See also 3
  • References 4
  • Further reading 5


As a genus, Chloroflexus spp. are type II photosynthetic reaction centers containing bacteriochlorophyll a similar to the purple bacteria, and light-harvesting chlorosomes containing bacteriochlorophyll c similar to green sulfur bacteria of the Chlorobi.

As the name implies, these anoxygenic phototrophs do not produce oxygen as a byproduct of photosynthesis, in contrast to oxygenic phototrophs such as cyanobacteria, algae, and higher plants. While oxygenic phototrophs use water as an electron donor for phototrophy, Chloroflexus uses reduced sulfur compounds such as hydrogen sulfide, thiosulfate, or elemental sulfur. This belies their antiquated name green non-sulfur bacteria, however Chloroflexus spp. can also utilize hydrogen(H2) as a source of electrons.

Chloroflexus aurantiacus is thought to grow photoautotrophic growth. Instead of using the Calvin-Benson-Bassham Cycle typical of plants, Chloroflexus aurantiacus has been demonstrated to use a novel autotrophic pathway known as the 3-Hydroxypropionate pathway.

The complete electron transport chain for Chloroflexus spp. is not yet known. Particularly, Chloroflexus aurantiacus has not been demonstrated to have a cytochrome bc1 complex, and may use different proteins to reduce cytochrome c

Evolution of photosynthesis

One of the main reasons for interest in Chloroflexus aurantiacus is in the study of the evolution of photosynthesis. As terrestrial mammals, we are most familiar with photosynthetic plants such as trees. However, photosynthetic eukaryotes are a relatively recent evolutionary development. Photosynthesis by eukaryotic organisms can be traced back to chloroplasts of trees still retain their own DNA as a molecular remnant that indicated their origin as photosynthetic bacteria.

The "respiration early" hypothesis

How did photosynthesis arise in bacteria? The answer to this question is complicated by the fact that there are several types of light-harvesting energy capture systems. Chloroflexus aurantiacus has been of interest in the search for origins of the so-called evolution of photosynthesis.

See also


Further reading

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