Marine microbes are major drivers of all elemental cycles. The processing of organic carbon by heterotrophic prokaryotes is tightly coupled to the availability of the trace element iron in large regions of the Southern Ocean. However, the functional diversity in iron and carbon metabolism within diverse communities remains a major unresolved issue. Using novel Southern Ocean meta-omics resources including 133 metagenome-assembled genomes (MAGs), we show a mosaic of taxonomy-specific ecological strategies in naturally iron-fertilized and high nutrient low chlorophyll (HNLC) waters. Taxonomic profiling revealed apparent community shifts across contrasting nutrient regimes. Community-level and genome-resolved metatranscriptomics evidenced a moderate association between taxonomic affiliations and iron and carbon-related functional roles. Diverse ecological strategies emerged when considering the central metabolic pathways of individual MAGs. Closely related lineages appear to adapt to distinct ecological niches, based on their distribution and gene regulation patterns. Our in-depth observations emphasize the complex interplay between the genetic repertoire of individual taxa and their environment and how this shapes prokaryotic responses to iron and organic carbon availability in the Southern Ocean.

海洋微生物是所有元素循环的主要驱动力。异养原核生物对有机碳的处理与南大洋大片区域微量元素铁的可用性密切相关。然而，不同群落中铁和碳代谢的功能多样性仍然是一个尚未解决的主要问题。使用包括 133 个宏基因组组装基因组 (MAG) 在内的新型南大洋宏组学资源，我们展示了自然施铁和高营养低叶绿素 (HNLC) 水域中分类学特定生态策略的镶嵌图。分类学分析揭示了不同营养体系之间明显的群落变化。社区水平和基因组解析的元转录组学证明了分类学隶属关系与铁和碳相关功能作用之间的适度关联。在考虑单个 MAG 的中心代谢途径时，出现了多种生态策略。根据它们的分布和基因调控模式，密切相关的谱系似乎适应不同的生态位。我们的深入观察强调了个体类群的遗传库与其环境之间复杂的相互作用，以及这如何影响原核生物对南大洋铁和有机碳可用性的反应。