The ability of aerobic microorganisms to regulate internal and external concentrations of the reactive oxygen species (ROS) superoxide directly influences the health and viability of cells. Superoxide dismutases (SODs) are the primary regulatory enzymes that are used by microorganisms to degrade superoxide. SOD is not one, but three separate, non-homologous enzymes that perform the same function. Thus, the evolutionary history of genes encoding for different SOD enzymes is one of convergent evolution, which reflects environmental selection brought about by an oxygenated atmosphere, changes in metal availability, and opportunistic horizontal gene transfer (HGT). In this study we examine the phylogenetic history of the protein sequence encoding for the nickel-binding metalloform of the SOD enzyme (SodN). A comparison of organismal and SodN protein phylogenetic trees reveals several instances of HGT, including multiple inter-domain transfers of the sodN gene from the bacterial domain to the archaeal domain. Nearly half of the archaeal members with sodN live in the photic zone of the marine water column. The sodN gene is widespread and characterized by apparent vertical gene transfer in some sediment-associated lineages within the Actinobacteriota (Actinobacteria) and Chloroflexota (Chloroflexi) phyla, suggesting the ancestral sodN likely originated in one of these clades before expanding its taxonomic and biogeographic distribution to additional microbial groups in the surface ocean in response to decreasing iron availability. In addition to decreasing iron quotas, nickel-binding SOD has the added benefit of withstanding high reactant and product ROS concentrations without damaging the enzyme, making it particularly well suited for the modern surface ocean.

中文翻译：

---

镍结合超氧化物歧化酶的域间水平基因转移

好氧微生物调节活性氧（ROS）超氧化物的内部和外部浓度的能力直接影响细胞的健康和生存能力。超氧化物歧化酶（SOD）是微生物用来降解超氧化物的主要调节酶。SOD不是一种酶，而是三种具有相同功能的独立的非同源酶。因此，编码不同SOD酶的基因的进化历史是趋同进化的过程之一，它反映了由氧化气氛，金属利用率和机会水平基因转移（HGT）带来的环境选择。在这项研究中，我们检查了编码SOD酶（SodN）的镍结合金属型的蛋白质序列的系统进化史。sodN基因从细菌域到古细菌域。具有sodN的古细菌成员中近一半生活在海水柱的光化带中。所述SODN基因很普遍，其特征在于由所述Actinobacteriota（放线菌）和Chloroflexota（绿弯菌门）门类内的一些沉积物相关谱系表观垂直的基因转移，表明祖SODN可能起源于这些进化枝中的一个进化枝，然后将其分类学和生物地理分布扩展到表层海洋中的其他微生物群，以应对铁的有效性下降。除减少铁配额外，与镍结合的SOD还具有承受高反应物和产物ROS浓度而又不损害酶的额外优势，使其特别适合于现代海面。