It is now widely accepted that siderophores play a role in marine iron biogeochemical cycling. However, the mechanisms by which siderophores affect the availability of iron from specific sources and the resulting significance of these processes on iron biogeochemical cycling as a whole have remained largely untested. In this study, we develop a model system for testing the effects of siderophore production on iron bioavailability using the marine copiotroph Alteromonas macleodii ATCC 27126. Through the generation of the knockout cell line ΔasbB::km^r, which lacks siderophore biosynthetic capabilities, we demonstrate that the production of the siderophore petrobactin enables the acquisition of iron from mineral sources and weaker iron-ligand complexes. Notably, the utilization of lithogenic iron, such as that from atmospheric dust, indicates a significant role for siderophores in the incorporation of new iron into marine systems. We have also detected petrobactin, a photoreactive siderophore, directly from seawater in the mid-latitudes of the North Pacific and have identified the biosynthetic pathway for petrobactin in bacterial metagenome-assembled genomes widely distributed across the global ocean. Together, these results improve our mechanistic understanding of the role of siderophore production in iron biogeochemical cycling in the marine environment wherein iron speciation, bioavailability, and residence time can be directly influenced by microbial activities.

现在人们普遍认为铁载体在海洋铁生物地球化学循环中发挥作用。然而，铁载体影响特定来源铁的有效性的机制以及这些过程对铁生物地球化学循环的整体意义在很大程度上仍未得到检验。在这项研究中，我们开发了一个模型系统，用于测试铁载体产生对铁生物利用度的影响，使用海洋共生菌Alteromonas macleodii ATCC 27126。通过产生敲除细胞系 Δ asbB ::km ^r，缺乏铁载体生物合成能力，我们证明了铁载体petrobactin的生产能够从矿物来源和较弱的铁-配体复合物中获得铁。值得注意的是，成岩铁的利用，例如来自大气尘埃的铁，表明铁载体在将新铁结合到海洋系统中的重要作用。我们还直接从北太平洋中纬度的海水中检测到了一种光反应性铁载体petrobactin，并在广泛分布于全球海洋的细菌宏基因组组装基因组中确定了petrobactin 的生物合成途径。总之，这些结果提高了我们对铁载体产生在海洋环境中铁生物地球化学循环中的作用的机械理解，其中铁物种形成，