Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331-4501, USA.
Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331-4501, USA.
FEMS Microbiol Ecol. 2018 Mar 1;94(3). doi: 10.1093/femsec/fiy008.
The factors influencing how soil nitrite (NO2-)- and ammonia (NH3)-oxidizing activities remain coupled are unknown. A short-term study (<48 h) was conducted to examine the dynamics of NO2--oxidizing activity and the accumulation of NO2- in three Oregon soils stimulated by the addition of 1 mM NH4+ in soil slurry. Nitrite initially accumulated in all three soils; its subsequent decline or slowing of the accumulation of the NO2- pool by 24 h was accompanied by an increase in the size of the nitrate (NO3-) pool, indicating a change in NO2- oxidation kinetics. Bacterial protein synthesis inhibitors prevented the NO2- pool decline, resulting in a larger accumulation in all three soils. Although no significant increases in NO2--oxidizing bacteria nxrA (Nitrobacter) and nxrB (Nitrospira) gene abundances were detected over the time course, maximum NO2- consumption rates increased 2-fold in the treatment without antibiotics compared to no change with antibiotics. No changes were observed in the apparent half saturation constant (Km) values for NO2- consumption. This study demonstrates phenotypic flexibility among soil NO2- oxidizers, which can undergo protein synthesis-dependent increases in NO2- consumption rates to match NH3 oxidation rates and recouple nitrification.
影响土壤亚硝酸盐（NO2--）和氨（NH3）氧化活性耦合的因素尚不清楚。本研究进行了一项为期较短（<48 h）的研究，以检验在添加 1 mM NH4+的土壤浆中，NO2--氧化活性和 NO2-在三种俄勒冈土壤中的动态变化及积累情况。在所有三种土壤中，NO2-最初都会积累；到 24 小时时，NO2-库的积累速度下降或减缓，同时硝酸盐（NO3-）库的大小增加，表明 NO2-氧化动力学发生了变化。细菌蛋白质合成抑制剂可防止 NO2-库的减少，从而导致所有三种土壤中 NO2-的积累量增加。尽管在整个时间过程中未检测到 nxrA（硝化杆菌）和 nxrB（硝化螺旋菌）基因丰度的显著增加，但与添加抗生素相比，无抗生素处理的 NO2-最大消耗率增加了两倍。NO2-消耗的表观半饱和常数（Km）值没有变化。本研究表明，土壤 NO2-氧化菌具有表型灵活性，可以通过依赖于蛋白质合成的方式增加 NO2-的消耗速率，以匹配 NH3的氧化速率并重新耦合硝化作用。
