P-062 - Linking lignin degradation and antimicrobial activity in Streptomyces

The degradation of plant-derived lignin plays a crucial role in soil structure and fertility. However, lignin degradation requires the secretion of exogenous enzymes that break lignin down into products accessible to other microbes, which incentivizes resource defense by lignin degraders. Streptomyces are known for producing antimicrobial secondary metabolites but can also degrade soil lignin. Here, we sought to understand the potential connections between antimicrobial metabolites and lignin utilization among Streptomyces. Specifically, are isolates that utilize lignin as a sole carbon source more inhibitory than isolates that do not? We collected 133 Streptomyces from the soil of 65-year corn monocultures which had been managed in a +/- fertilizer by +/- residue removal factorial design. From these we determined the ability of isolates to utilize lignin and sequenced the 16S region. Using a random subset of 24 lignin-utilizing and 24 non-utilizing isolates we measured the zone of inhibition of each isolate against ten Streptomyces standards. Lignin-degrading Streptomyces had a larger zone of inhibition than non-lignin-degrading populations in plots with residue retained, while fertilizer application was associated with a smaller effect size in regard to zones of inhibition. Lignin utilization was phylogenetically clustered. Our results suggest Streptomyces that can degrade lignin and inhibit target populations may offer multi-functional pathways for the suppression of plant disease via direct inhibition of pathogens and the degradation of infectious crop residues.