Knowledge of the behavior of microbial communities in ecosystems is limited, yet microbes control partly all element cycles and, in turn, processes influencing pollution and climate change. In particular, heterotrophic denitrification is major process controlling the transformation of nitrogen oxides pollutants, e.g. nitrates (NO₄^-) and nitrous oxide (N₂O), a greenhouse gas. Iron acts as either nutrient or stress in denitrifying microbial communities, yet underlying mechanisms are unclear. We hypothesized that iron plays a vital role in the assembly process of heterotrophic denitrifying microbial communities. To test this hypothesis we cultivated 17 microcosms under carbon- and iron-rich conditions. Geochemical analysis, 16S rRNA gene high-throughput sequencing, and multivariate statistical analysis were implemented to unravel the driving forces that shape the assembly process of microbial communities. Results reveal that iron was the most dominant factor influencing the diversity and composition of heterotrophic denitrifying communities, versus pH, C/N, temperature, nitrate reduction, and iron oxidation rates. Higher Fe concentration induced more clustered microbial interactions. Heterotrophic microbial community assembly is shaped by 90% stochastic processes, whereas deterministic processes rose with Fe(II) concentration. Overall our findings demonstrate that iron controls the balance between the deterministic and stochastic processes of heterotrophic denitrifying microbial communities. These mechanisms may have implications for bioremediation strategies.

对生态系统中微生物群落行为的了解是有限的，但是微生物部分控制了所有元素循环，进而控制了污染和气候变化的过程。特别地，异养硝化是主要过程中控制氮氧化物污染物，例如硝酸盐（NO的转化₄ ^- ）和一氧化二氮（N ₂O），一种温室气体。铁在反硝化微生物群落中充当营养物或压力，但其潜在机制尚不清楚。我们假设铁在异养反硝化微生物群落的组装过程中起着至关重要的作用。为了验证该假设，我们在富含碳和铁的条件下培养了17个微观世界。进行了地球化学分析，16S rRNA基因高通量测序和多元统计分析，以揭示影响微生物群落装配过程的驱动力。结果表明，铁是影响异养反硝化群落多样性和组成的最主要因素，与pH，C / N，温度，硝酸盐还原和铁的氧化速率相比。高铁浓度会引起更多的簇生微生物相互作用。异养微生物群落的组装是由90％的随机过程决定的，而确定性过程随Fe（II）浓度的增加而增加。总的来说，我们的发现表明，铁控制着异养反硝化微生物群落的确定性过程和随机过程之间的平衡。这些机制可能会对生物修复策略产生影响。