Widespread detoxifying NO reductases impart a distinct isotopic fingerprint on N2O under anoxia.
Widespread detoxifying NO reductases impart a distinct isotopic fingerprint on N2O under anoxia.
复制标题
广泛存在的解毒 NO 还原酶在缺氧条件下赋予 N2O 独特的同位素指纹。
DOI：
10.1101/2023.10.13.562248
复制
发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Newman,DianneK
中科院分区：
文献类型：
--
作者：
Wang,RenéeZ;Lonergan,ZacheryR;Wilbert,StevenA;Eiler,JohnM;Newman,DianneK
一氧化二氮(N2O)是一种强有力的温室气体，在不同的环境中可以由多种生物和非生物过程产生。准确追踪N2O的主要来源有可能提高我们对土壤中N2O通量的理解，并为人类感染的诊断提供信息。由于细菌和真菌的一氧化氮还原酶(NORs)产生的N2O具有不同的同位素指纹，跨越了很大的范围，因此已为此目的使用了同位素“位置偏好”(SP)值。在这里，我们发现黄色素是一种迄今被忽视但分布广泛的解毒细菌NO还原酶，它在缺氧条件下(~+10‰)赋予N2O一个独特的SP值，这与典型的环境N2O SP测量结果相关联。利用铜绿假单胞菌作为模式生物，我们产生了只含有FHP或异化NOR的菌株，发现这些酶在体内产生的N2O SP值相差10‰以上。根据细胞的生理状态，野生型细胞中FHP：NOR的比例显著变化，并控制净N2O SP生物特征：当细胞在反硝化条件下厌氧生长时，不占主导地位；当细胞在缺氧条件下经历迅速增加的一氧化氮浓度但不生长时，FHP占主导地位。其他只使FHP产生与Our P测量的N2O SP生物特征相似的细菌。铜绿假单胞菌。目前，在已测序的细菌基因组中，FHP同源物超过NOR同源物近四倍。因此，我们提出了一个不同的框架来指导自然和疾病中N2O生物来源的归属。
Nitrous oxide (N2O), a potent greenhouse gas, can be generated by multiple biological and abiotic processes in diverse contexts. Accurately tracking the dominant sources of N2O has the potential to improve our understanding of N2O fluxes from soils as well as inform the diagnosis of human infections. Isotopic “Site Preference” (SP) values have been used toward this end, as bacterial and fungal nitric oxide reductases (NORs) produce N2O with different isotopic fingerprints, spanning a large range. Here, we show that flavohemoglobin (Fhp), a hitherto biogeochemically neglected yet widely distributed detoxifying bacterial NO reductase, imparts a distinct SP value onto N2O under anoxic conditions (~+10‰) that correlates with typical environmental N2O SP measurements. UsingPseudomonas aeruginosaas a model organism, we generated strains that only contained Fhp or the dissimilatory NOR, finding that in vivo N2O SP values imparted by these enzymes differ by over 10‰. Depending on the cellular physiological state, the ratio of Fhp:NOR varies significantly in wild-type cells and controls the net N2O SP biosignature: When cells grow anaerobically under denitrifying conditions, NOR dominates; when cells experience rapid, increased nitric oxide concentrations under anoxic conditions but are not growing, Fhp dominates. Other bacteria that only make Fhp generate similar N2O SP biosignatures to those measured from ourP. aeruginosaFhp-only strain. Fhp homologs in sequenced bacterial genomes currently exceed NOR homologs by nearly a factor of four. Accordingly, we suggest a different framework to guide the attribution of N2O biological sources in nature and disease.