Potential roles of anaerobic ammonium and methane oxidation in the nitrogen cycle of wetland ecosystems

Abstract

Anaerobic ammonium oxidation (anammox) and anaerobic methane oxidation (ANME coupled to denitrification) with nitrite as electron acceptor are two of the most recent discoveries in the microbial nitrogen cycle. Currently the anammox process has been relatively well investigated in a number of natural and man-made ecosystems, while ANME coupled to denitrification has only been observed in a limited number of freshwater ecosystems. The ubiquitous presence of anammox bacteria in marine ecosystems has changed our knowledge of the global nitrogen cycle. Up to 50% of N 2 production in marine sediments and oxygendepleted zones may be attributed to anammox bacteria. However, there are only few indications of anammox in natural and constructed freshwater wetlands. In this paper, the potential role of anammox and denitrifying methanotrophic bacteria in natural and artificial wetlands is discussed in relation to global warming. The focus of the review is to explore and analyze if suitable environmental conditions exist for anammox and denitrifying methanotrophic bacteria in nitrogen-rich freshwater wetlands.

Nitrite-dependent anaerobic methane oxidizing bacteria along the water level fluctuation zone of the Three Gorges Reservoir

“…The low level of nitrite may be explained by a high turnover rate. It was hypothesized that n-damo bacteria cooperated with denitrifying bacteria which reduce nitrate to nitrite or with ammonium oxidizing bacteria (Hu et al 2011;Zhu et al 2010). In this case, the higher content of ammonium in lower sites suggested a high possibility of the cooperation between n-damo bacteria and ammonium oxidizing bacteria or archaea.…”

“…The results of this study showed that the population of n-damo bacteria can still grow in a natural environment after water flooding for a long time creating anoxic conditions. It was hypothesized that n-damo bacteria depend on redox gradients at oxic-anoxic interfaces in their natural environments (Zhu et al 2010). In addition, our results showed that the anaerobic condition and availability of ammonium would be of great significance to n-damo bacteria.…”

Evidence for nitrite-dependent anaerobic methane oxidation as a previously overlooked microbial methane sink in wetlands

“…The n-damo is predicted to occur near the oxic-anoxic interface, having low concentrations of oxidizable substrates other than methane, as well as low level of sulfate and high level of nitrate (16). Such conditions prevail in anoxic wetlands (17). To date, however, there have been no reports of direct evidence for the occurrence of n-damo in wetlands.…”

“…Extracted DNA was then examined using 1.0% agarose gel electrophoresis. The 16S rRNA and pmoA genes of M. oxyfera-like bacteria were amplified using nested PCR protocols as previously described (17,32). Detailed information on the primers used is provided in Table S2.…”

Spatial distribution of archaeal and bacterial ammonia oxidizers in the littoral buffer zone of a nitrogen-rich lake

“…The littoral buffer zone harbors a changing environment between land and water, which suggests a complex microbial nitrification (Zhu et al, 2010. However, knowledge about the ammonia oxidizing communities in the littoral buffer zone remains unclear, but is essential for us to understand the N cycle.…”