Electron transport chains and bioenergetics of respiratory nitrogen metabolism in Wolinella succinogenes and other Epsilonproteobacteria.
Recent phylogenetic analyses have established that the Epsilonproteobacteria form a globally ubiquitous group of ecologically significant organisms that comprises a diverse range of free-living bacteria as well as host-associated organisms like Wolinella succinogenes and pathogenic Campylobacter and Helicobacter species. Many Epsilonproteobacteria reduce nitrate and nitrite and perform either respiratory nitrate ammonification or denitrification. The inventory of epsilonproteobacterial genomes from 21 different species was analysed with respect to key enzymes involved in respiratory nitrogen metabolism. Most ammonifying Epsilonproteobacteria employ two enzymic electron transport systems named Nap (periplasmic nitrate reductase) and Nrf (periplasmic cytochrome c nitrite reductase). The current knowledge on the architecture and function of the corresponding proton motive force-generating respiratory chains using low-potential electron donors are reviewed in this article and the role of membrane-bound quinone/quinol-reactive proteins (NapH and NrfH) that are representative of widespread bacterial electron transport modules is highlighted. Notably, all Epsilonproteobacteria lack a napC gene in their nap gene clusters. Possible roles of the Nap and Nrf systems in anabolism and nitrosative stress defence are also discussed. Free-living denitrifying Epsilonproteobacteria lack the Nrf system but encode cytochrome cd(1) nitrite reductase, at least one nitric oxide reductase and a characteristic cytochrome c nitrous oxide reductase system (cNosZ). Interestingly, cNosZ is also found in some ammonifying Epsilonproteobacteria and enables nitrous oxide respiration in W. succinogenes.
Kern
Melanie
M
Institute of Molecular Biosciences, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany.
Simon
Jörg
J
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D016123:Campylobacter jejuni / Q000235:genetics / Q000378:metabolism; D045263:Cytochromes a1 / Q000235:genetics / Q000378:metabolism; D003575:Cytochromes c1 / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport; D004734:Energy Metabolism; D020565:Epsilonproteobacteria / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D008954:Models, Biological; D005810:Multigene Family; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D019897:Periplasm / Q000201:enzymology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D016968:Wolinella / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D000644:Quaternary Ammonium Compounds; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; D050901:Nitrate Reductase; C054690:nitrate reductase (cytochrome); D009609:Nitrous Oxide; D009584:Nitrogen