Nitrite, an Electron Donor for Anoxygenic Photosynthesis

摘要

Although compounds of the sulfur cycle, and more recently the iron cycle, are well-studied electron donors for anoxygenic photosynthesis, no analogous oxidations in the nitrogen cycle are known. We report a previously unknown process in which anoxygenic photo-trophic bacteria use nitrite as an electron donor for photosynthesis, providing a microbial mechanism for the stoichiometric oxidation of nitrite to nitrate in the absence of oxygen. To examine nitrite as a possible electron donor for anoxygenic photo-trophs, we established enrichment cultures derivedrnfrom local sewage sludge and several freshwater sediments in anoxic, bicarbonate-buffered mineral medium (ⅰ). Low amounts of nitrite (1 to 2 mM) were fed repeatedly to avoid toxicity, and the cultures were incubated continuously in the light.