Temperature and oxygen level determine N₂O respiration activities of heterotrophic N₂O‐reducing bacteria: Biokinetic study

Abstract

Nitrous oxide (N2O), a potent greenhouse gas, is reduced to N2 gas by N2O‐reducing bacteria (N2ORB), a process which represents an N2O sink in natural and engineered ecosystems. The N2O sink activity by N2ORB depends on temperature and O2 exposure, yet the specifics are not yet understood. This study explores the effects of temperature and oxygen exposure on biokinetics of pure culture N2ORB. Four N2ORB, representing either clade I type nosZ (Pseudomonas stutzeri JCM5965 and Paracoccus denitrificans NBRC102528) or clade II type nosZ (Azospira sp. strains I09 and I13), were individually tested. The higher activation energy for N2O by Azospira sp. strain I13 (114.0 ± 22.6 kJ mol−1) compared with the other tested N2ORB (38.3–60.1 kJ mol−1) indicates that N2ORB can adapt to different temperatures. The O2 inhibition constants (KI) of Azospira sp. strain I09 and Ps. stutzeri JCM5965 increased from 0.06 ± 0.05 and 0.05 ± 0.02 μmol L−1 to 0.92 ± 0.24 and 0.84 ± 0.31 μmol L−1, respectively, as the temperature increased from 15°C to 35°C, while that of Azospira sp. strain I13 was temperature‐independent (p = 0.106). Within the range of temperatures examined, Azospira sp. strain I13 had a faster recovery after O2 exposure compared with Azospira sp. strain I09 and Ps. stutzeri JCM5965 (p < 0.05). These results suggest that temperature and O2 exposure result in the growth of ecophysiologically distinct N2ORB as N2O sinks. This knowledge can help develop a suitable N2O mitigation strategy according to the physiologies of the predominant N2ORB.

Clarifying Microbial Nitrous Oxide Reduction under Aerobic Conditions: Tolerant, Intolerant, and Sensitive

“…Besides N 2 O reduction rates, microorganisms with low K m values, such as P. denitrificans and D. aromatica , could be useful in scavenging low concentrations of dissolved N 2 O. It is important to note, however, that the kinetics and O 2 sensitivity of N 2 O reducers can be influenced by environmental factors, such as the type of organic carbons ( 30 ) and temperature ( 31 ). Therefore, when selecting appropriate N 2 O reducers for engineering applications, their N 2 O reduction kinetics and O 2 sensitivity should be measured under environmentally relevant conditions.…”

Clarifying Microbial Nitrous Oxide Reduction Under Aerobic Conditions: Tolerant, Intolerant, and Sensitive

“…Besides N 2 O reduction rates, microorganisms with low K m values, such as Pa. denitrificans and D. aromatica , could be useful in scavenging low concentrations of dissolved N 2 O. It is important to note, however, that the kinetics and O 2 sensitivity of N 2 O reducers can be influenced by environmental factors such as the type of organic carbons [28] and temperature [29]. Therefore, when selecting appropriate N 2 O reducers for engineering applications, their N 2 O reduction kinetics and O 2 sensitivity should be measured under environmentally relevant conditions.…”

“…Azospirillum brasilense strains were also used as a microbial inoculant for N 2 O mitigation in soil. [27] Nevertheless, engineering applications of biological that the kinetics and O 2 sensitivity of N 2 O reducers can be influenced by environmental factors such as the type of organic carbons [28] and temperature [29]. Therefore, when selecting appropriate N 2 O reducers for engineering applications, their N 2 O reduction kinetics and O 2 sensitivity should be measured under environmentally relevant conditions.…”

Insights into the mechnisms of the differential abilities of two N2O reducers, Pseudomonas sp., isolated from paddy soil

“…In the present study, it was observed that although DM15 and DM22 belong to the same genus of Pseudomonas, they performed significantly different N2O reducing abilities. Since it has been reported that environmental factors could lead to the functional differentiations of denitrifying bacteria, such as temperature, oxygen level, pH and C/N [23,26,29,30], whether the functional difference of these strains was related to environmental conditions? The results of the present study indicated that either under anaerobic and aerobic or varied temperature conditions, DM15 regardless performed higher N2O reducing ability than DM22, which suggested that environmental factors would not be the main reason for their differential N2O reducing abilities.…”

“…However, it was also indicated that some aerobic denitrifiers exhibited relatively strong N2O reducing efficiency under oxic condition [20,21], such as Pseudomonas, Azospirillum, Herbaspirillum, Marinobacter [22][23][24][25][26]. The suitable pH and temperature for N2O reducing isolates were between 6-8 and 15-35°C [27][28][29][30], respectively. Out of these ranges the N2O reducing activities were obviously restricted.…”