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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.

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A series of new lanthanoid thioarsenates [Ln(teta)(μ-η(1):η(2):η(1)-As(III)S3)]n {Ln = Ce (Ia), Pr (Ib), Nd (Ic), and Sm (Id); teta = triethylenetetramine} and [Ln(teta)(en)(μ-η(1):η(1):η(1)-As(V)S4)]n {Ln = La (IIa), Ce (IIb), Pr (IIc), and Nd (IId); en = ethylenediamine} were prepared by the solvothermal reaction of K3AsO3, S, LnCl3 and organic amines and structurally characterized. Compounds Ia–d crystallise in the orthorhombic space group Aba2 and display 1-D neutral chains [Ln(teta)(μ-η(1):η(2):η(1)-As(III)S3)]n, which represent the first examples of 1-D organic hybrid lanthanoid sulfides built up from trigonal-pyramidal [As(III)S3](3-) acting as tetradentate bridging ligands to interlink [Ln(teta)](3+) ions, while compounds IIa–d crystallise in the orthorhombic space group P2(1)2(1)2(1) and consist of other 1-D neutral chains [Ln(teta)(en)(μ-η(1):η(1):η(1)-As(V)S4)]n, which are built up from the linkages of the tetrahedral [As(V)S4](3-) ion and the [Ln(teta)(en)](3+) ion. To learn more about the influence of lanthanide contraction on the formation of lanthanoid thioarsenates, three organic hybrid lanthanoid thioarsenates [Ln(teta)(en)As(V)S4] [Ln = Dy (IIIa), Ho (IIIb), and Tm (IIIc)] with the neutral molecular structure type in the monoclinic centrosymmetric space group P2(1)/c are also presented. Their optical and magnetic properties have been investigated, and density functional theory calculations of Ia and IIa have also been performed.