Methanogenesis: Syntrophic Metabolism
Syntrophy is a mutualistic interaction in which two metabolically different types of microorganisms are linked by the need to keep metabolites exchanged between the two partners at low concentrations to make the overall metabolism of both organisms feasib
- PDF / 348,056 Bytes
- 20 Pages / 439.37 x 666.142 pts Page_size
- 86 Downloads / 167 Views
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
2
Importance of Syntrophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
3
Bioenergetic Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
4
Interspecies Electron Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
5 5.1 5.2 5.3 5.4
Biochemical Pathways for Syntrophic Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Acetate Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Propionate Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Butyrate Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 Benzoate Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
6
Potential Mechanisms for Reverse Electron Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
7
Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
K. N. Timmis (ed.), Handbook of Hydrocarbon and Lipid Microbiology, DOI 10.1007/978-3-540-77587-4_22, # Springer-Verlag Berlin Heidelberg, 2010
338
22
Methanogenesis: Syntrophic Metabolism
Abstract: Syntrophy is a mutualistic interaction in which two metabolically different types of microorganisms are linked by the need to keep metabolites exchanged between the two partners at low concentrations to make the overall metabolism of both organisms feasible. In most cases, the cooperation is based on the transfer of hydrogen, formate, or acetate from fermentative bacteria to methanogens to make the degradation of electron-rich substrates thermodynamically favorable. Syntrophic metabolism proceeds at very low Gibbs’ free energy changes, close to the minimum free energy change needed to conserve energy biologically, which is the energy needed to transport one proton across the cytoplasmic membrane. Pathways for syntrophic degradation of fatty acids predict the net synthesis of about onethird of an ATP per round of catabolism. Syntrophic metabolism entails critical oxidationreduction reactions in which hydrogen or formate production would be thermodynamically unfavorable unless energy is invested. The membrane processes involved in ion translocation and reverse electron transport are poorly understood. While much evidence supports interspecies transfer of hydrogen and formate, other mechanisms of interspecies ele
Data Loading...
