Cyanobacterial mats were hotspots of biogeochemical cycling during the Precambrian. However, mechanisms that controlled O₂ release by these ecosystems are poorly understood. In an analog to Proterozoic coastal ecosystems, the Frasassi sulfidic springs mats, we studied the regulation of oxygenic and sulfide-driven anoxygenic photosynthesis (OP and AP) in versatile cyanobacteria, and interactions with sulfur reducing bacteria (SRB). Using microsensors and stable isotope probing we found that dissolved organic carbon (DOC) released by OP fuels sulfide production, likely by a specialized SRB population. Increased sulfide fluxes were only stimulated after the cyanobacteria switched from AP to OP. O₂ production triggered migration of large sulfur-oxidizing bacteria from the surface to underneath the cyanobacterial layer. The resultant sulfide shield tempered AP and allowed OP to occur for a longer duration over a diel cycle. The lack of cyanobacterial DOC supply to SRB during AP therefore maximized O₂ export. This mechanism is unique to benthic ecosystems because transitions between metabolisms occur on the same time scale as solute transport to functionally distinct layers, with the rearrangement of the system by migration of microorganisms exaggerating the effect. Overall, cyanobacterial versatility disrupts the synergistic relationship between sulfide production and AP, and thus enhances diel O₂ production.

蓝藻垫是前寒武纪生物地球化学循环的热点。然而，对这些生态系统控制 O ₂释放的机制知之甚少。在类似于元古代沿海生态系统的 Frasassi 硫化泉垫中，我们研究了多功能蓝藻中含氧和硫化物驱动的无氧光合作用（OP 和 AP）的调节，以及与硫还原细菌 (SRB) 的相互作用。使用微传感器和稳定同位素探测，我们发现 OP 释放的溶解有机碳 (DOC) 促进了硫化物的产生，可能是由专门的 SRB 种群产生的。仅在蓝藻从 AP 转变为 OP 后，硫化物通量的增加才受到刺激。氧₂生产引发了大型硫氧化细菌从表面迁移到蓝藻层下方。生成的硫化物屏蔽使 AP 回火并允许 OP 在一个柴油循环中发生更长的持续时间。因此，AP 期间 SRB 缺乏蓝藻 DOC 供应使 O ₂输出最大化。这种机制是底栖生态系统所独有的，因为新陈代谢之间的转变发生在与溶质向功能不同的层运输相同的时间尺度上，微生物迁移对系统的重新排列夸大了这种影响。总体而言，蓝藻的多功​​能性破坏了硫化物生产和 AP 之间的协同关系，从而提高了 diel O ₂的生产。