Only about 10%–30% of the organic matter produced in the epipelagic layers reaches the dark ocean. Under these limiting conditions, reduced inorganic substrates might be used as an energy source to fuel prokaryotic chemoautotrophic and/or mixotrophic activity. The aprA gene encodes the alpha subunit of the adenosine-5′-phosphosulfate (APS) reductase, present in sulfate-reducing (SRP) and sulfur-oxidizing prokaryotes (SOP). The sulfur-oxidizing pathway can be coupled to inorganic carbon fixation via the Calvin–Benson–Bassham cycle. The abundances of aprA and cbbM, encoding RuBisCO form II (the key CO₂ fixing enzyme), were determined over the entire water column along a latitudinal transect in the Atlantic from 64°N to 50°S covering six oceanic provinces. The abundance of aprA and cbbM genes significantly increased with depth reaching the highest abundances in meso- and upper bathypelagic layers. The contribution of cells containing these genes also increased from mesotrophic towards oligotrophic provinces, suggesting that under nutrient limiting conditions alternative energy sources are advantageous. However, the aprA/cbbM ratios indicated that only a fraction of the SOP is associated with inorganic carbon fixation. The aprA harbouring prokaryotic community was dominated by Pelagibacterales in surface and mesopelagic waters, while Candidatus Thioglobus, Chromatiales and the Deltaproteobacterium_SCGC dominated the bathypelagic realm. Noticeably, the contribution of the SRP to the prokaryotic community harbouring aprA gene was low, suggesting a major utilization of inorganic sulfur compounds either as an energy source (occasionally coupled with inorganic carbon fixation) or in biosynthesis pathways.

中文翻译：

---

介导大西洋硫循环的微生物及其与化能自养的联系


表层产生的有机物中只有约 10%–30% 到达暗海。在这些限制条件下，还原的无机底物可以用作能源来促进原核化学自养和/或混合营养活性。 apr A 基因编码腺苷-5'-磷酸硫酸盐 (APS) 还原酶的 α 亚基，存在于硫酸盐还原 (SRP) 和硫氧化原核生物 (SOP) 中。硫氧化途径可以通过卡尔文-本森-巴沙姆循环与无机碳固定耦合。编码RuBisCO II型（关键的CO ₂固定酶）的apr A和cbb M的丰度是在大西洋纬度横断面（从64°N到50°S）覆盖六个海洋省份的整个水柱上测定的。 apr A 和cbb M 基因的丰度随着深度的增加而显着增加，在中深海层和上深海层达到最高丰度。含有这些基因的细胞的贡献也从中营养省向寡营养省增加，这表明在营养限制条件下替代能源是有利的。然而， apr A/ cbb M 比率表明，只有一小部分 SOP 与无机碳固定有关。 apr A 的原核生物群落在表层和中层水域以 Pelagibacterales 为主，而在深海区域则以Candidatus Thioglobus、Chromatiales 和 Deltaproteobacteres_SCGC 为主。 值得注意的是，SRP 对含有apr A 基因的原核生物群落的贡献较低，表明无机硫化合物主要用作能源（偶尔与无机碳固定相结合）或用于生物合成途径。