RESUMEN
IMPORTANCE: Wetlands are globally significant carbon cycling hotspots that both sequester large amounts of CO2 as soil carbon as well as emit a third of all CH4 globally. Their outsized role in the global carbon cycle makes it critical to understand microbial processes contributing to carbon breakdown and storage in these ecosystems. Here, we confirm the presence of chain-elongating organisms in freshwater wetland soils. These organisms take small carbon compounds formed during the breakdown of biomass and turn them into larger compounds (six to eight carbon organic acids) that may potentially contribute to the formation of soil organic matter and long-term carbon storage. Moreover, we find that these chain-elongating organisms may be widely distributed in wetlands globally. Future work should identify these organisms' contribution to carbon cycling in wetlands and the potential role of the products they form in carbon sequestration in wetlands.
