自然界中能发生光合作用的生物一定具备光系统1和光系统2吗? 第1页

不一定。进行产氧光合作用的地球生物具有光系统 Ⅰ 和光系统 Ⅱ，进行不产氧光合作用的地球生物具有单一光系统，既不是光系统 Ⅰ 也不是光系统 Ⅱ。

以下引自 G. Unden 的 Encyclopedia of Biological Chemistry (Second Edition), 2013 年：

Anoxygenic Photosynthetic Prokaryotes

Anoxygenic photosynthetic bacteria use only one photosystem for converting light energy into an electrochemical proton potential, which is then used for driving ADP phosphorylation. Anoxygenic photosynthetic bacteria are found in three different phylogenetic groups, which contain different photosynthetic systems: the purple bacteria, the green phototrophic bacteria with the subgroups of green sulfur bacteria (Chlorobiaceae) and Chloroflexus, and the Gram-positive Heliobacteria. The three groups show differences in the type of photosynthetic reaction center, photosynthetic electron transfer and the electron donors, pigments, and the pathway for CO2 fixation. In anoxygenic photosynthesis, light is used to raise electrons to a more electronegative redox potential and to feed the electrons into a cyclic electron transport to generate a proton potential. The bacteria contain only one reaction center in contrast to oxygenic photosynthesis in cyanobacteria, green algae, or plants. The photosystems of anoxic photosynthesis transfer the electrons either to quinones or to ferredoxin (quinone-type- or FeS-type reaction centers). The archaeon Halobacterium salinarum, on the other hand, contains a proton pump that is directly driven by light to translocate protons over the membrane without involvement of photosynthetic electron transport. In contrast to the photosynthetic bacteria that use chlorophyll containing proteins for photosynthesis and energy conversion, Halobacterium contains bacteriorhodopsin with retinal as a chromophore for light absorption and conversion to an electrochemical proton potential.

另外，某些蚜虫和叶螨似乎可以吸收少量太阳辐射产生 ATP。那似乎还没发展为光合作用。