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Discovery of Ubiquitous Photoheterotrophs - Coggle Diagram
Discovery of Ubiquitous Photoheterotrophs
Early 2000s
Aerobic anoxygenic photosynthetic bacteria (AAPB), contained bacteriochlorophyll (BChl) a
also recognised as a photosynthetic pigment in anaerobic anoxygenic photosynthetic bacteria (AnAPB)
Proteorhodopsin-containing bacteria
Both bacteria are photoheterotrophs without carbon fixation & never been recognized as primary producers
AAPB
derived from non-sulfur purple bacteria, AnAPB in the a-Proteobacteria
the amount reached up to 30% of the total primary production(some specific lakes)
grow (photo-)heterotrophycally in an aerobic environment
the same with AnAPB that they contain BChl a
aerobic & require molecular oxygen for their growth and BChl a synthesis
distributes widely in euphotic zone
AnAPB
traditionally understood to distribute in anaerobic environment & perform photosynthesis without oxygen evolution
Proteorhodopsin
Rhodopsin-like protein detected in marine Proteobacteria
a retial-opsin complex in a member of rhodopsin
Opsin is a bundle of seven transmembrane a-helices
Retinal, vitamin A aldehyde binds to the lysine residue at the central pocket of the opsin
Rhodopsin is well known as a photoreceptor in vertebrates as a light sensor
One rhodopsin-like protein was known to contibute to adenosine triphosphate (ATP) synthesis
a large amount and wide variety of rhodopsin-like genes were detected in seawater by metagenomic analysis
The gene was expressed in
E. coli
and acted to form transmembrane proton electrochemical gradients for ATP synthesis under light