Broda E
J Mol Evol. 1975 Dec 31;7(1):87-100. doi: 10.1007/BF01732182.
When in the primeval atmosphere ammonia approached exhaustion, bacteria resembling clostridia developed mechanisms for nitrogen fixation. The fixation was continued by the photosynthetic bacteria. In the later, oxidizing, atmosphere the combined activities of the nitrificants and the denitrificants could lead to a large-scale cyclic regeneration of free nitrogen. The possibility of a descent of the nitrificants from hypothetical photosynthetic bacteria, which used ammonia as electron donor, is discussed. The anoxygenic atmosphere contained no nitrate, and therefore neither nitrate fermentation nor nitrate respiration were precursors of aerobic respiration. This evolved from photosynthesis. In nitrate fermentation, nitrate serves only as an incidental electron acceptor; this process is merely an evolutionary sideline. Nitrate respiration evolved from aerobic respiration. While in present conditions the reaction of nitrogen with oxygen and water to give nitrate is exergonic and possibly occurs at a low rate, the antagonistic action of the denitrificants maintains the stationary concentrations of nitrogen and oxygen in the air.
在原始大气中，当氨接近耗尽时，类似梭菌的细菌发展出了固氮机制。光合细菌继续进行固氮作用。在后来的氧化大气中，硝化菌和反硝化菌的联合活动可导致游离氮的大规模循环再生。文中讨论了硝化菌可能起源于以氨为电子供体的假想光合细菌的可能性。无氧大气中不含硝酸盐，因此，硝酸盐发酵和硝酸盐呼吸都不是有氧呼吸的前身。有氧呼吸是从光合作用进化而来的。在硝酸盐发酵中，硝酸盐仅作为偶然的电子受体；这个过程仅仅是进化的旁支。硝酸盐呼吸是从有氧呼吸进化而来的。虽然在当前条件下，氮与氧和水反应生成硝酸盐的反应是放能的，且可能以较低速率发生，但反硝化菌的拮抗作用维持了空气中氮和氧的稳定浓度。
