Transcriptional and environmental control of bacterial denitrification and N2O emissions

Abstract

In oxygen-limited environments, denitrifying bacteria can switch from oxygen-dependent respiration to nitrate (NO3-) respiration in which the NO3- is sequentially reduced via nitrite (NO2-), nitric oxide (NO) and nitrous oxide (N2O) to dinitrogen (N2). However, atmospheric N2O continues to rise, a significant proportion of which is microbial in origin. This implies that the enzyme responsible for N2O reduction, nitrous oxide reductase (NosZ), does not always carry out the final step of denitrification either efficiently or in synchrony with the rest of the pathway. Despite a solid understanding of the biochemistry underpinning denitrification, there is a relatively poor understanding of how environmental signals and respective transcriptional regulators control expression of the denitrification apparatus. This minireview describes the current picture for transcriptional regulation of denitrification in the model bacterium, Paracoccus denitrificans, highlighting differences in other denitrifying bacteria where appropriate, as well as gaps in our understanding. Alongside this, the emerging role of small regulatory RNAs in regulation of denitrification is discussed. We conclude by speculating how this information, aside from providing a better understanding of the denitrification process, can be translated into development of novel greenhouse gas mitigation strategies.

Biochar as electron donor for reduction of N2O by Paracoccus denitrificans

“…The ability of P. denitrificans to generate N 2 O is well known (Gaimster et al . 2018 ). However, under an anoxic atmosphere and NO 3 − -limited conditions, its major denitrification product is N 2 (Felgate et al .…”

Diversifying Anaerobic Respiration Strategies to Compete in the Rhizosphere

“…However, only a few studies have been interested in understanding anaerobic respiration in the rhizosphere (Philippot et al, 1995;Ghiglione et al, 2000;Mirleau et al, 2001). Denitrification represents the most studied one area, likely due to its large contribution to the increase of N 2 O emissions, a gas that has an approximately 300-fold greater impact on global warming than CO 2 (Bakken et al, 2012;Domeignoz-Horta et al, 2015;Gaimster et al, 2018) . In the next paragraph, we review the different mechanisms of anaerobic respiration encountered in the environment and we attempt to determine whether certain respiration processes studied in a given environment can take place in the rhizosphere by the microbiota associated with plants.…”

The role of conserved proteins DrpA and DrpB in nitrate respiration of Thermus thermophilus

“…Denitrification is a complex anaerobic respiration pathway driven through four enzymatic steps, in which nitrogen oxides are successively reduced from nitrate to nitrite, nitric oxide, nitrous oxide and finally dinitrogen by consecutive action of the corresponding Nar, Nir, Nor and Nos reductases. As oxygen is a better electron acceptor, expression of the denitrification enzymes is subjected to hierarchical transcriptional control by oxygen, with the presence of an appropriate nitrogen oxide also required (Zumft, 1997;Richardson and Watmough, 1999;Gaimster et al, 2018).…”