Nitrate/nitrite-dependent
anaerobic methane oxidation (n-DAMO)
is critical for mitigating methane emission and returning reactive
nitrogen to the atmosphere. The genomes of n-DAMO archaea show that
they have the potential to couple anaerobic oxidation of methane to
dissimilatory nitrate reduction to ammonium (DNRA). However, physiological
details of DNRA for n-DAMO archaea were not reported yet. This work
demonstrated n-DAMO archaea coupling the anaerobic oxidation of methane
to DNRA, which fueled Anammox in a methane-fed membrane biofilm reactor
with nitrate as only electron acceptor. Microelectrode analysis revealed
that ammonium accumulated where nitrite built up in the biofilm. Ammonium
production and significant upregulation of gene expression for DNRA
were detected in suspended n-DAMO culture with nitrite exposure, indicating
that nitrite triggered DNRA by n-DAMO archaea. 15N-labeling
batch experiments revealed that n-DAMO archaea produced ammonium from
nitrate rather than from external nitrite. Localized gradients of
nitrite produced by n-DAMO archaea in biofilms induced ammonium production
via the DNRA process, which promoted nitrite consumption by Anammox
bacteria and in turn helped n-DAMO archaea resist stress from nitrite.
As biofilms predominate in various ecosystems, anaerobic oxidation
of methane coupled with DNRA could be an important link between the
global carbon and nitrogen cycles that should be investigated in future
research.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.