A review of syntrophic fatty acids oxidation in anoxic paddy soil

Abstract:

Flooded rice field is one of major biogenic sources of greenhouse gas CH4. Complex organic matter is degraded to CH4 and CO2 by the co-operation of anaerobic microorganisms of several metabolic guilds involving the syntrophic oxidation of short-chain fatty acids like propionate, butyrate and acetate. Due to the fastidious nature of cultivation, the diversity and ecology of microorganisms involved in syntrophic oxidation in natural environments like paddy soils remain largely unexplored. Stable isotope probing (SIP), which links microbial identity and function, is a powerful tool to investigate the syntrophic oxidation of fatty acids in flooded paddy soils. This article reviews the recent research progresses in the thermodynamic principles, the interspecies interactions in the syntrophic oxidation of fatty acids, and paddy soils employing SIP technology. The knowledge acquired suggests that phylogenetically diverse bacterial groups are active in the syntrophic oxidation: except classic syntrophic bacteria, organisms belonging to uncultivated phylogenetic groups are also detected, which can serve as candidate syntrophs. Among archaea, Methanocella is the major methanogen partner in syntrophic oxidation of different fatty acids, indicating the importance of this group in CH4 production of paddy field soil.