Chloroflexus aurantiacus is a photosynthetic bacterium isolated from hot springs, belonging to the green non-sulfur bacteria.

are filamentous anoxygenic phototrophic (FAP) organisms that utilize 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 Chlorobiota.

Chloroflexota), the species stains Gram negative, yet has a single lipid layer (monoderm),[2] but with thin peptidoglycan, which is compensated for by S-layer protein.

Chloroflexus aurantiacus is thought to grow photoheterotrophically in nature, but it has the capability of fixing inorganic carbon through photoautotrophic growth.

Chloroflexus aurantiacus has been of interest in the search for origins of the so-called type II photosynthetic reaction center.