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Aerobic anoxygenic photoheterotrophic bacteria (AAPB), also named aerobic anoxygenic photoheterotrophs (AAPs), is a group of bacteria that are primarily heterotrophic but can utilize light energy through bacterial chlorophyll a.

Description
In contrast to other known anoxygenic phototrophs, these microbes are obligatory aerobes: They metabolize carbon and other organic substrates and use O2-dependent respiration, but they also contain bacteriochlorophyll a, carotenoids, as well as photosynthetic reaction centers and light-harvesting complexes. Although the amount of bacteriochlorophyll in these photoheterotrophs is lower than in other photosynthetic bacteria, they are capable of fixing CO2 during photosynthesis, and light enhances their growth. Their ancestors appear to be purple nonsulfur bacteria, and they have arisen independently several times during evolution. So far, they have not attracted much attention, although they are abundant in organic-rich sediments (on the surface of seaweeds) and in seawater.

Distribution
They are widely distributed in coastal and oceanic environments. They can also be abundant in various oligotrophic conditions, including the most oligotrophic regime of the world ocean. They are globally distributed in the euphotic zone and represent a hitherto unrecognized component of the marine microbial community that appears to be critical to the cycling of both organic and inorganic carbon in the ocean.

Evolution and Taxonomy
Aerobic anoxygenic phototrophic bacteria are classified in two marine (Erythrobacter and Roseobacter) and six freshwater (Acidiphilium, Erythromicrobium, Erythromonas,Porphyrobacter, Roseococcus, and Sandaracinobacter) genera, which phylogenetically belong to the -1, -3, and -4 subclasses of the class Proteobacteria. Phylogenetically, they are not classified into single group. Species so far described are distributed rather widely within the α-subclass of Proteobacteria (purple bacteria) in which most of the purple nonsulfur bacteria as well as many non-photosynthetic bacteria are included. Apparently, these aerobic BChl-containing bacteria represent an evolutionary transient phase from anaerobic phototrophs to aerobic non-phototrophs. However, some characteristic features distinct from anaerobic phototrophs suggest that most of them are in a evolutionary stable state.

Reference
Nianzhi Jiao, Gerhard J. Herndl, Dennis A. Hansell, Ronald Benner, Gerhard Kattner, Steven W. Wilhelm, David L. Kirchman, Markus G. Weinbauer, Tingwei Luo, Feng Chen, Farooq Azam (2010). "Microbial Production of Recalcitrant Dissolved Organic Matter: Long-term Carbon Storage in the Global Ocean". Nature Reviews Microbiology 8, 593-599. dio: 10. 1038/nrmicro2386.

Tom Fenchel (2001). "Marine Bugs and Carbon Flow". Science 29: 2444-2445. doi:10. 1126. Rapheal Lami, Matthew T. Cottell, Josephine Ras, Osvaldo Ulloa, Ingrid Obernosterer, Herve Claistre, David L. Kirchman, Philippe Lebaron (2007). "High Abundances of Aerobic Anoxygenic Photosynthetic Bacteria in the South Pacific Ocean". Applied and Environmental Microbiology 73 (13), 4198-4205. doi: 10.1128/AEM. 02652-06.

Zbigniew S. Kolber, F. Gerald, Plumley, Andrew S. Lang, J. Thomas beatty, Robert E. Blankenship, Cindy L. Vandover, Costantino Vetriani, Michal Koblizek, Christopher Rathgeber, Paul G. Falkowsik (2001). "Contribution of Aerobic Photoheterotrophic Bacteria to the Carbon Cycle in the Ocean". Science 29: 2492-2495. doi: 10.1126.

Vladimir V. Yurkov, J. Thomas Beatty (1998). "Aerobic Anoxygenic Phototrophic Bacteria". Microbiology and Molecular Biology Reviews, 62 (3): 1092-2172.

Keizo Shimada (2004). "Aerobic Anoxygenic Phototrophs". Advances in Photosynthesis and Respiration, 2(1), 105-122. doi: 10.1007.