Genomic insights and antifungal potential of Pseudomonas species isolated from maple sap, including the novel species Pseudomonas acericola sp. nov. and Pseudomonas edsoni sp. nov.

Fungal contamination poses a significant challenge in maple sap collection systems and postproduction processes, which affects the quality and shelf life of maple syrup. As an alternative to chemical treatments, microorganisms offer promising biocontrol potential. This study investigates nine Pseudomonas strains isolated from maple sap for their antifungal activity and genomic features. Whole-genome sequencing followed by comparative genomic analysis identified five distinct Pseudomonas species, including two previously uncharacterized taxa for which we propose the names Pseudomonas acericola sp. nov. and Pseudomonas edsoni sp. nov., in accordance with the nomenclatural guidelines of the SeqCode. Strain distributions from metagenome recruitment suggest they originate from sapwood, and previous metataxonomic data show that the amplicon sequence variant matching P. edsoni predominated maple sap samples. Genome mining using antiSMASH and BAGEL4 identified gene clusters associated with the synthesis of antifungal compounds, such as hydrogen cyanide, siderophores, cyclic lipopeptides, and ribosomally synthesized peptides. Antifungal assays demonstrated inhibitory activity against food spoilage fungi, with P. edsoni strains being active against Kluyveromyces lactis. The absence of activity in the cell-free supernatant and the presence of Type VI secretion systems in the genomes point toward contact-dependent mechanisms. Collectively, these findings reveal previously unrecognized taxonomic diversity and ecological specialization in maple sap-associated Pseudomonas, providing a basis for the rational development of Pseudomonas-based antifungal strategies in maple syrup production and quality control.