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Fundamentals and Modeling Aspects of Bioventing
Published in Subhas K. Sikdar, Robert L. Irvine, Fundamentals and Applications, 2017
C. M. Tellez, A. Aguilar-Aguila, R. G. Arnold, R. Z. Guzman
There are five genera in this group: Nitrosomonas, Nitrosococcus, Nitrospira, Nitrosolobus, and Nitrosovibrio. The best studied species of ammonia oxidizers is Nitrosomonas europaea, an obligate chemolitho-troph that initiates nitrification by the reductant-dependent oxidation of ammonia to hydroxylamine using ammonia monooxygenase (AMO). Reductant for AMO-catalyzed reactions is provided by the further oxidation of hydroxylamine to nitrite by hydroxylamine oxidoreductase (Figure 6). There is evidence that the AMO of N. europaea can also initiate cometabolic transformation of hydrocarbons (Hyman and Wood, 1983; 1984) and haloaliphatic compounds, including TCE (Arciero et al., 1989; Vanelli et al., 1990). The situation is entirely parallel to that of the methanotrophs in that halogenated substrates are transformed by both AMO and MMO without any direct metabolic benefit. Both enzymes consume reductant in the process, which must be replenished by metabolic activities at some expense to the organisms. For this reason, a primary or energy-yielding substrate is necessary for sustained cometabolic activity.
Short Term Effects of Various Salts on Ammonia and Nitrite Oxidisers in Enriched Bacterial Cultures
Published in Moustafa Samir Moussa, Nitrification in Saline Industrial Wastewater, 2014
Ammonia oxidisers. Hunik et al (1992) investigated the inhibitory effect of substrate (NH4C1), different salts (KC1, NaCl) and the end product on a pure culture of Nitrosomonas europaea (ATCC 19718) at similar environmental conditions (30°C, pH 7.5). They observed no significant distinction between the different salts, substrates or end products and concluded that osmotic pressure, due to the high salt concentration, is the explanation for the reduction in activity. They proposed a formula to describe the inhibition of salt on the activity of ammonia oxidisers as a function of salt concentration (equation 3.1). () ActualammoniaoxidisersactivityMaximumammoniaoxidisersactivity⋅100%=99.4−0.187⋅mMsalt
Agricultural Soils: Nitrous Oxide Emissions
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Soils and Terrestrial Systems, 2020
The process of nitrification is normally defined as the biological oxidation of ammonium to nitrate with nitrite as an intermediate.[4] The first step in the reaction, the oxidation of ammonium to nitrite, is carried out mainly by the microorganism Nitrosomonas. The second step, oxidation of nitrite to nitrate, is carried out by Nitrobacter. It has been shown in a number of publications that Nitrosomonas europaea produces nitrous oxide during the oxidation of ammonium.[4]
Niche specialization of comammox Nitrospira in terrestrial ecosystems: Oligotrophic or copiotrophic?
Published in Critical Reviews in Environmental Science and Technology, 2023
Chaoyu Li, Zi-Yang He, Hang-Wei Hu, Ji-Zheng He
All ammonia and hydroxylamine oxidation-related genes in comammox Nitrospira have high similarity to those of AOB, indicating the comparable ammonia oxidation mechanisms between these two phylogenetically separate nitrifying groups (Daims et al., 2015; Koch et al., 2019; van Kessel et al., 2015). Comammox Nitrospira, AOA and AOB all harbor the three polypeptide subunits of AMO (grouped in amoCAB) converting ammonia into hydroxylamine (NH2OH). In comammox Nitrospira and AOB, the intermediate NH2OH is subsequently converted into NO2− by HAO, but no HAO homologs are found in AOA (Beeckman et al, 2018; Koch et al., 2019). A biochemical study on the HAO of Nitrosomonas europaea related AOB proposed that nitric oxide (NO) might be also a product of hydroxylamine oxidation, acting as “NH2OH/NO obligate intermediate model” (Caranto & Lancaster 2017). The participation of a third enzyme in the conversion of NO to NO2− is implied in this model (Caranto & Lancaster 2017). Based on the common sequences encoding AMO and HAO, a similar ammonia oxidation pathway containing NO as an obligate intermediate was suggested in AOB and comammox Nitrospira (Koch et al., 2019). Contrary to β-AOB containing two or three copies of amo and hao gene clusters, comammox Nitrospira genomes possess an individual gene cluster of the central ammonia oxidation pathway operons (Palomo et al., 2018). Comammox Nitrospira are most closely related to AOB (Daims et al., 2015; van Kessel et al., 2015). The amo and hao gene sequences have higher similarities between β-AOB and comammox Nitrospira than those between β-AOB and γ-AOB (Palomo et al., 2018). A reconciliation analysis investigated the evolutionary history of amoA genes further confirmed a strong possibility of gene transfers from β-AOB to the ancestor of comammox Nitrospira (Palomo et al., 2018). The different niche adaptations of comammox Nitrospira clades A and B may contribute to the high dissimilarity of their amoA sequences. The pairwise dissimilatory sequence analysis showed that the evolution rate of the proteins related to the ammonia oxidation pathway in comammox Nitrospira clade B is faster than those in clade A (Palomo et al., 2018). The evolved genetic features of comammox Nitrospira, together with the different genomic characterization of clade A and B indicate that the two clades may have a broad distribution and be not necessarily limited in oligotrophic habitats.