The desire to understand and distinguish the relative growth and activity of ammonia oxidising archaea (AOA) and ammonia oxidising bacteria (AOB) in soil nitrification has increased the search for selective inhibitors of these two groups. This study aimed to investigate the potency and specificity of simvastatin as a specific AOA inhibitor in pure cultures and in soil and to determine the effect of AOA inhibition on both ammonia oxidation activity and growth of AOB, under the hypothesis that AOB growth is higher when competition for NH₄⁺ from AOA is removed. Simvastatin selectively inhibited pure cultures of all tested AOA at concentrations of 8–100 μM. In soil microcosms incubated for 21 days with low and high NH₄⁺ concentrations, AOA but not AOB were selectively inhibited by simvastatin in both acidic (pH 4.5) and near-neutral (pH 6.5) soils. Additionally, growth of AOB significantly increased at both NH₄⁺ concentrations following inhibition of AOA by simvastatin, suggesting that competition for substrate between AOA and AOB is a key factor restraining AOB growth in NH₄⁺-limited soils. Simvastatin can therefore be used as a selective AOA inhibitor to investigate kinetic characteristics of AOB in soils and to study competition between AOA and AOB in complex environments.

了解和区分氨氧化古细菌（AOA）和氨氧化细菌（AOB）在土壤硝化中的相对生长和活性的愿望增加了对这两组的选择性抑制剂的寻找。这项研究旨在研究辛伐他汀作为一种特定的AOA抑制剂在纯培养物和土壤中的效力和特异性，并确定AOA抑制对氨氧化活性和AOB生长的影响（假设竞争时AOB的生长较高）从AOA中除去NH ₄ ^+的方法。辛伐他汀选择性地抑制所有测试的AOA的纯培养物，浓度为8-100μM。在低和高NH ₄ ⁺孵育21天的土壤微观世界中在酸性（pH 4.5）和接近中性（pH 6.5）的土壤中，辛伐他汀选择性抑制AOA而不是AOB的浓度。此外，辛伐他汀抑制AOA后，两种NH ₄ ⁺浓度下AOB的生长均显着增加，这表明AOA和AOB之间对底物的竞争是限制NH ₄ ⁺受限土壤中AOB生长的关键因素。因此，辛伐他汀可以用作选择性AOA抑制剂，以研究土壤中AOB的动力学特性，并研究复杂环境中AOA与AOB之间的竞争。