Characteristics and comparisons of the aerobic and anaerobic denitrification of a Klebsiella oxytoca strain: Performance, electron transfer pathway, and mechanism

• Published in: Journal of environmental management 2023-07, Vol.338, p.117787-117787, Article 117787
• Main Authors: Ju, Cheng-jia, Niyazi, Shareen, Cao, Wen-yin, Wang, Quan, Chen, Rong-ping, Yu, Lei
• Format: Article
• Language: English
• Subjects: Aerobic denitrification; Aerobiosis; Anaerobic denitrification; Anaerobiosis; Denitrification; Electron transfer pathway; Electrons; Heterotrophic Processes; Klebsiella oxytoca; Klebsiella oxytoca - genetics; Klebsiella oxytoca - metabolism; Nitrates; Nitrification; Nitrite Reductases - genetics; Nitrite Reductases - metabolism; Nitrites - metabolism; Nitrogen - metabolism; Nitrogen Dioxide
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.117787

The performance and electron (e−) transfer mechanisms of anaerobic and aerobic denitrification by strain Klebsiella were investigated in this study. The RT-PCR results demonstrated that the membrane bound nitrate reductase gene (narG) and Cu-nitrite reductase gene (nirK) were responsible for both aerobic and anerobic denitrification. The extreme low gene relative abundance of nirK might be responsible for the severe accumulation of NO2−-N (nitrogen in the form of NO2− ion) under anaerobic condition. Moreover, the nitrite reductase (Nir) activity was 0.31 μg NO2−-N min−1 mg−1 protein under anaerobic conditions, which was lower than that under aerobic conditions (0.38 μg NO2−-N min−1 mg−1 protein). By using respiration chain inhibitors, the e- transfer pathways of anaerobic and aerobic denitrification of Klebsiella strain were constructed. Fe–S protein and Complex III were the core components under anaerobic conditions, while Coenzyme Q (CoQ), Complexes I and III played a key role in aerobic denitrification. Nitrogen assimilation was found to be the main way to generate NH4+-N (nitrogen in the form of NH4+ ion) during anaerobic denitrification, and also served as the primary nitrogen removal way under aerobic condition. The results of this study may help to improve the understanding of the core components of strain Klebsiella during aerobic and anaerobic denitrifications, and may suggest potential applications of the strain for nitrogen-containing wastewater. [Display omitted] •Denitrifications were achieved by Klebsiella under anaerobic and aerobic conditions.•Gene relative abundances of nirK were negligible under anaerobic condition.•Higher nitrite reductase activity was detected under aerobic condition.•Assimilation is the main removal pathway of nitrogen under aerobic denitrification.•The e− transfer pathways of denitrification by Klebsiella strain were constructed.