Abstract

This review summarizes discoveries in syntrophic propionate degradation research and reveals intriguing metabolic capabilities, mechanisms of cooperation and environmentally driven kinetics by taxonomically distinct microorganisms that are important for biotechnological applications and biogenic methane emissions.The mutual nutritional cooperation underpinning syntrophic propionate degradation provides a scant amount of energy for the microorganisms involved, so propionate degradation often acts as a bottleneck in methanogenic systems. Understanding the ecology, physiology and metabolic capacities of syntrophic propionate-oxidizing bacteria (SPOB) is of interest in both engineered and natural ecosystems, as it offers prospects to guide further development of technologies for biogas production and biomass-derived chemicals, and is important in forecasting contributions by biogenic methane emissions to climate change. SPOB are distributed across different phyla. They can exhibit broad metabolic capabilities in addition to syntrophy (e.g. fermentative, sulfidogenic and acetogenic metabolism) and demonstrate variations in interplay with cooperating partners, indicating nuances in their syntrophic lifestyle. In this review, we discuss distinctions in gene repertoire and organization for the methylmalonyl-CoA pathway, hydrogenases and formate dehydrogenases, and emerging facets of (formate/hydrogen/direct) electron transfer mechanisms. We also use information from cultivations, thermodynamic calculations and omic analyses as the basis for identifying environmental conditions governing propionate oxidation in various ecosystems. Overall, this review improves basic and applied understanding of SPOB and highlights knowledge gaps, hopefully encouraging future research and engineering on propionate metabolism in biotechnological processes.

Keywords

propionic acid; syntrophy; methanogenesis; methylmalonyl-CoA pathway; interspecies electron transfer; anaerobic digestion

Published in

FEMS Microbiology Reviews
2022, Volume: 46, number: 2, article number: fuab057
Publisher: OXFORD UNIV PRESS

SLU Authors

• Westerholm, Maria

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Microbiology


Publication identifier

DOI: https://doi.org/10.1093/femsre/fuab057

Permanent link to this page (URI)

https://res.slu.se/id/publ/116473