In search of Comammox in oxygen limiting conditions

Master thesis (2020)

Authors

M. LU Applied Sciences

Contributors

R. Kleerebezem BT/Environmental Biotechnology - AS (supervisor 1)
G.R. Stouten BT/Environmental Biotechnology - AS (supervisor 1)
D.G. Weissbrodt BT/Environmental Biotechnology - AS (supervisor 2)
J.B. van Lier Sanitary Engineering - CEG (supervisor 2)
Faculty
Applied Sciences
Copyright: © 2020 Mu-En LU
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Published Date

24-08-2020

Language

English

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Faculty

Applied Sciences

Abstract

Comammox bacteria are capable of catalysing the full nitrification pathway – oxidation of ammonium to nitrate – and have been encountered in many ecosystems recently (Lawson & Lücker, 2018). What the ecological role of comammox bacteria is in hypoxic enrichment cultures remains unclear. Based on the thermodynamics and biochemistry of known nitrogen cycle conversion, we propose that comammox is oxidizing ammonium to nitrite with both oxygen and nitrate as electron acceptor in hypoxic condition. Our hypothesis suggests that when comammox cooperates with anammox, they can harvest most energy per unit of oxygen supplied. We tried to cultivate bacteria toward a community of anammox and comammox consortium by limiting the oxygen and supplying ammonium and nitrate. Although the predicted optimal state has not been achieved during this work, we did observe that the community indeed developed towards higher consumption of ammonium under limited oxygen supply.