Table 1.

Characteristics of oxygenic and anoxygenic photosynthesis.

Oxygenic photosynthesis	Anoxygenic photosynthesis
Light-driven transmembrane electron transfer	Light-driven transmembrane electron transfer
Coupled to proton translocation	Coupled to proton translocation
Including a proton-motive Q-cycle through a cytochrome b-f complex	Including a proton-motive Q-cycle through a cytochrome b-c1 complex
Two photosystems or “light reactions”: Type I (PS I) and Type II (PS II)	One photosystem or “light reaction” of either Type I or Type II.
Includes non-cyclic electron transport pathway with H2O as the initial electron donor	Non-cyclic electron transport pathway with inorganic electron donors (e.g., H2S, Fe2+, H2) or organic electron donors (e.g., succinate, acetate, and pyruvate).
Special case of the van Niel equation	Other special cases of the van Niel equation
Carbon dioxide fixation by the Benson–Calvin pathway (a.k.a. reductive pentose phosphate pathway)	Carbon dioxide fixation by the Benson–Calvin pathway (a.k.a. reductive pentose phosphate pathway) OR by other pathways such as the “reverse” (i.e., reductive) TriCarboxylic Acid cycle
Makes oxygen	Inhibited by oxygen
In cyanobacteria and chloroplasts	In purple and green photosynthetic bacteria, and heliobacteria
Resulted in the Great Oxidation (or Event; oxygen-rich atmosphere and eventually oceans; aerobic respiration; ozone layer and life on land; end of MIFS and BIFS from Fe2+→Fe3+; N as nitrite/nitrate; S as sulfide/sulfate; eukaryotes; multicellularity	Resulted in increased biomass in coastal microbial mats and stromatolites as free energy input from sunlight added to geochemical sources.
Appeared at the Archaean to (paleo)proterozoic boundary ∼2.5 Gyr (or earlier if “whiffs of O2” are real and a signature)	Appeared early in the Archaean eon from 3.8 Gyr