Energiekonservierung in methanogenen Archaea, die im menschlichen Darm vorkommen
Zusammenfassung der Projektergebnisse
Methanomassiliicoccus luminyensis was originally isolated from human feces and belongs to the seventh order of methanogens, the Methanomassiliicoccales, which are only distantly related to other methanogenic archaea. The organism forms methane from the reduction of methylamines or methanol using molecular hydrogen as reductant. The energy-conserving system in M. luminyensis is unique and the enzymes involved in this process are not found in this combination in members of the other methanogenic orders. In this context our central question was how the organism is able to generate ATP. In the course of the project it became evident that the energy transduction of the organisms was dependent on a membrane-bound ferredoxin: heterodisulfide oxidoreductase composed of reduced ferredoxin as an electron donor, the Fpo complex (a homolog of complex 1 (NDH1) of aerobic respiratory chains) and the heterodisulfide reductase HdrD, which reduced the electron acceptor CoM- S-S-CoB. Electron transfer of this respiratory chain proceeded with a rate of 145 nmol reduced heterodisulfide min^-1 mg^-1 membrane protein. M. luminyensis is the first example of a methanogenic archaeon that does not require Na+ ions for energy conservation. Only protons were used as coupling ions for the generation of the electrochemical ion gradient. In summary, the energy-conserving system of M. luminyensis possesses features found in the pathways of hydrogenotrophic and methylotrophic/aceticlastic methanogenesis. Consequently, the composition of the enzymes involved in ion translocation across the cytoplasmic membrane is different from all other methanogenic archaea. FpoF is the electron accepting module of the Fpo complex of Methanosarcina mazei, which transfers electrons from the methanogenic electron carrier F420 to FpoI as membrane-associated subunit of the complex. FpoF can also be produced heterologously in E. coli and is thus available in large quantities for enzyme measurements. It became evident that this subunit in combination with reduced cofactor F420 was able to channel electrons also into the respiratory chain of E. coli and the gut bacterium Prevotella copri. FpoF was very likely to react with a membrane component other than the NDH1 complex of the organisms. Nevertheless, it was interesting to see that a methanogenic protein (FpoF) allows the use of a methanogenic cofactor (F420H2) in a bacterial respiratory chain.
Projektbezogene Publikationen (Auswahl)
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(2019) Energy conservation in the gut microbe Methanomassiliicoccus luminyensis is based on membrane-bound ferredoxin oxidation coupled to heterodisulfide reduction. FEBS J. 286 (19): 3831-3843
Kröninger L, Steiniger F, Berger S, Kraus S, Welte CU, Deppenmeier U
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(2019) Long-term investigation of microbial community composition and transcription patterns in a biogas plant undergoing ammonia crisis. Microb Biotechnol. 12(2):305-323
Fischer MA, Güllert S, Refai S, Künzel S, Deppenmeier U, Streit WR, Schmitz RA
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(2022) Process of energy-conservation in the extremely haloalkaliphilic methyl-reducing methanogen Methanonatronarchaeum thermophilum. FEBS J. 289(2): 549-563
Steiniger F, Sorokin DY, Deppenmeier U
