SynCom-mediated herbicide degradation activates microbial carbon metabolism in soils

Extensive herbicide residues in the black soil of northeastern China are considered a significant agricultural pollution threat, yet effective bioremediation of this complex and persistent mixture remains a challenge. We identified 16 bacterial species that associated with these herbicide residues in situ, nine of which were culturable and could degrade multiple herbicides. From these strains, we constructed a four-member synthetic microbial community (SynCom) that degrades multiple herbicides, stabilizes colonization, increases soil bacterial biodiversity, and alters soil enzyme activity. Under laboratory conditions, the SynCom degraded eight herbicides within 48 h with >60% efficiency, and accumulated carbon on the cell surface of the constituent species. In black soil microcosm trials, the SynCom achieved 60%-99% degradation efficiency of the endogenous herbicides over 35 days and was able to consistently maintain biomass above 10⁴ cfu/g soil. Additionally, SynCom application resulted in an accumulation of carbohydrate-active enzymes and microbial necromass-associated carbon, which suggests activation of soil microbial carbon metabolism. In support of this, metagenomic analyses identified a significant increase in the abundance of genes involved in the tricarboxylic acid cycle, pyruvate metabolism, and glycolysis. This SynCom represents a compelling bioremediation solution that simultaneously improves soil microbial carbon metabolism activity in polluted soils.