Denitrification causes nitrogen losses from terrestrial ecosystems. The magnitude of nitrogen loss depends on the prevalence of denitrifiers, which show ecological differences if they harbour nirS or nirK genes encoding nitrite reductases with the same biological function. Thus, it is relevant to understand the mechanisms of co-existence of denitrifiers, including their response to environmental filters and competition due to niche similarities. We propose a framework to analyse the co-existence of denitrifiers across multiple assemblages by using nir gene-based co-occurrence networks. We applied it in Mediterranean soils before and during 1 year after an experimental fire. Burning did not modify nir community structure, but significantly impacted co-occurrence patterns. Bacteria with the same nir co-occurred in space, and those with different nir excluded each other, reflecting niche requirements: nirS abundance responded to nitrate and salinity, whereas nirK to iron content. Prior to fire, mutual exclusion between bacteria with the same nir suggested competition due to niche similarities. Burning provoked an immediate rise in mineral nitrogen and erased the signals of competition, which emerged again within days as nir abundances peaked. nir co-occurrence patterns can help infer the assembly mechanisms of denitrifying communities, which control nitrogen losses in the face of ecological disturbance.

• MeSH
• Bacteria genetika   metabolismus   MeSH
• denitrifikace genetika   fyziologie   MeSH
• dusičnany metabolismus   MeSH
• dusík metabolismus   MeSH
• ekosystém MeSH
• nitritreduktasy genetika   metabolismus   MeSH
• požáry * MeSH
• půda chemie   MeSH
• půdní mikrobiologie MeSH
• salinita MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• dusičnany MeSH
• dusík MeSH
• nitritreduktasy MeSH
• půda MeSH

A new method of determination of nitrate was developed, utilizing the nitrate reductase activity of Paracoccus denitrificans in which a further reduction of nitrate is blocked either by a mutation affecting formation of cytochromes c or by inhibition of the electron flow to nitrite reductase by mucidin. After deproteinization of the sample with zinc acetate the nitrite produced is determined colorimetrically.

• MeSH
• dusičnany analýza   metabolismus   MeSH
• dusitany metabolismus   MeSH
• mutageneze MeSH
• nitrátreduktasa MeSH
• nitrátreduktasy metabolismus   MeSH
• nitritreduktasy genetika   metabolismus   MeSH
• Paracoccus denitrificans genetika   metabolismus   MeSH
• stabilita enzymů MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dusičnany MeSH
• dusitany MeSH
• nitrátreduktasa MeSH
• nitrátreduktasy MeSH
• nitritreduktasy MeSH