O2 versus N2O respiration in a continuous microbial enrichment

Abstract

Despite its ecological importance, essential aspects of microbial N2O reduction—such as the effect of O2 availability on the N2O sink capacity of a community—remain unclear. We studied N2O vs. aerobic respiration in a chemostat culture to explore (i) the extent to which simultaneous respiration of N2O and O2 can occur, (ii) the mechanism governing the competition for N2O and O2, and (iii) how the N2O-reducing capacity of a community is affected by dynamic oxic/anoxic shifts such as those that may occur during nitrogen removal in wastewater treatment systems. Despite its prolonged growth and enrichment with N2O as the sole electron acceptor, the culture readily switched to aerobic respiration upon exposure to O2. When supplied simultaneously, N2O reduction to N2 was only detected when the O2 concentration was limiting the respiration rate. The biomass yields per electron accepted during growth on N2O are in agreement with our current knowledge of electron transport chain biochemistry in model denitrifiers like Paracoccus denitrificans. The culture’s affinity constant (KS) for O2 was found to be two orders of magnitude lower than the value for N2O, explaining the preferential use of O2 over N2O under most environmentally relevant conditions.Electronic supplementary materialThe online version of this article (10.1007/s00253-018-9247-3) contains supplementary material, which is available to authorized users.

System characterization of dynamic biological cultivations through improved data analysis

“…These characterizations were used to correlate changes in community composition with changes in observed bioreactor performance (34). The Particle Filter implementation demonstrated here, was used to reconstruct the respiration rates in a wide range of dynamically operated bioreactors, varying from aerobic pulse-fed bioreactors (34), anaerobic bubble columns (37), anoxic N 2 O respiration (38), aerobic/anaerobic fermentations (39), isotope labeled studies for identification of novel pathways (40), and in chain elongation studies (41). The applicability of this reconstruction tool contributes to the identification of functional properties of biological processes in dynamic environments.…”

Involvement of the cbb3-Type Terminal Oxidase in Growth Competition of Bacteria, Biofilm Formation, and in Switching between Denitrification and Aerobic Respiration

“…Our results indicate that these differences may be of a quantitative rather than qualitative nature, reflecting changes in the proportion between electron transfer capabilities of the reducing and oxidizing branches of the respiratory chain. Conthe et al [ 33 ] related the preferential use of O 2 over N 2 O observed in a natural mixed culture to the fact that the Monod half-saturation constant ( K s ) value for O 2 was 1-2 orders of magnitude smaller compared to K s (N 2 O). Although we found a clear association between deletion of the high-affinity oxidase and appearance of aerobic denitrification, the explanation based on the change in affinity for oxygen does not apply in our case because the effect of oxidase deletion persists even at high oxygen concentrations that saturate all terminal oxidases present.…”

Using isotope pool dilution to understand how organic carbon additions affect N2O consumption in diverse soils

“…Organic matter additions have been the focus of many N 2 O management studies (Hellman et al, 2019; Lazcano et al, 2021; Senbayram et al, 2012; Stevenson et al, 2011; Sutton‐Grier et al, 2011; Wang, Amon, et al, 2021; Wu et al, 2018). N 2 O consumption is primarily an anaerobic, respiratory pathway (Hein & Simon, 2019; Shan et al, 2021), and so there exists an environmental correlation where N 2 O consumption rates are highest when both O 2 concentrations are low and organic matter abundance is high (Conthe et al, 2018; Senbayram et al, 2012; Wu et al, 2013, 2018). However, studies have found that the net emission of N 2 O can go either up or down, depending on the soil and the nature of the organic matter addition.…”