Syntrophy in Methanogenic Degradation

Abstract

This chapter deals with microbial communities of bacteria and archaea which closely cooperate in methanogenic degradation and perform metabolic functions in this community that neither one of them could carry out alone. The methanogenic degradation of fatty acids, alcohols, most aromatic compounds, amino acids, and others is performed in partnership between fermenting bacteria and methanogenic Archaea. The energy available in these processes is very small, attributing only fractions of an ATP unit per reaction run to every partner. The biochemical strategies taken include in most cases reactions of substrate-level phosphorylation combined with various kinds of reversed electron transport systems in which part of the gained ATP is reinvested into thermodynamically unfavorable electron transport processes. Altogether, these systems represent fascinating examples of energy efficiency at the lowermost energy level that allows microbial life.