Chloroflexus is a anoxygenic, filamentous, gliding bacterium found in the green non-sulfur branch in the 16s rRNA tree of life (however, not all Chloroflexus are green and unable to use sulfide). Generally, Chloroflexus is a photogeterotroph and uses organic molecules that are made from other bacteria, but some Chloroflexus strains grow autotrophically and use hydrogen or sulfide as an electron donor. Chloroflexus aurantiacus, which is a facultative aerobic species of Chloroflexus, can do anoxygenic photosynthesis that has characteristics of both green sulfur bacteria and purple bacteria (both of which are not closely related to Chloroflexus) as well as cellular respiration in aerobic environments. However, Chloroflexus bacteria, unlike purple bacteria, lack internal membranes. Chloroflexus aurantiacus also fix CO2 differently from other phototrophs though a pathway called the 3-hydroxypropionate pathway as well as they seem to lack ribulose bisphosphate carboxylase activity. In anaerobic (or semiaerobic) situations, Chloroflexus aurantiacus harvests light in chlorosomes that are slightly smaller that those of green sulfur bacteria and can be found pressed against the cell membrane. The chlorosomes, like those in green sulfur bacteria, contain bacteriochlorophyll c; in addition, light-harvesting complexes containing bacteriochlorophyll a (like in purple bacteria) can be found within the cell membrane. Also like purple bacteria, Chloroflexus bacteria have pheophytin-quione type photochemical reaction centers. (Sprague et al. 1981)