Seasonal metabolomics and antibacterial activity of Abutilon pannosum reveal positive interaction with the lytic phage CF01 against Escherichia coli O157:H7 (strain 161-84).

INTRODUCTION: Seasonal variation can influence plant metabolite composition and modify antimicrobial performance; however, the relationship between seasonal metabolomic changes and antibacterial activity remains poorly understood in many arid-land medicinal plants. To our knowledge, this is the first study to integrate GC-MS metabolomics, antibacterial screening, and phage-extract interaction testing in Abutilon pannosum.

METHODS: Leaf extracts of Abutilon pannosum collected during late summer (S1, September 2024), autumn (S2, November 2024), and winter (S3, February 2025) were analyzed using GC-MS. Antibacterial activity was evaluated against selected bacterial isolates using diffusion-based assays and MIC/MBC determination. The interaction between seasonal extracts and phage CF01 was further assessed against Escherichia coli O157:H7 under sub-MIC extract concentrations.

RESULTS: GC-MS analysis resolved the curated dataset into 350 putatively annotated parent metabolites, and PCA demonstrated clear season-dependent metabolomic separation, with 16 metabolites differing significantly among collection periods. S2 exhibited the broadest diversity of literature-supported antibacterial candidates, including α-linolenic acid, citronellol, dodecanoic acid, farnesol, ferulic acid, and 4-hydroxybenzoic acid, whereas S3 was enriched in caffeic acid, p-coumaric acid, D-limonene, and xylitol. Antibacterial activity varied according to season and bacterial isolate, with Staphylococcus aureus showing the highest susceptibility, while Escherichia coli exhibited weaker direct sensitivity. Phage-extract interaction assays demonstrated that CF01 enhanced Escherichia coli O157:H7 suppression at sub-MIC extract concentrations, particularly when extract-only treatment resulted in incomplete bacterial inhibition, with stronger enhancement patterns observed for S2 and S3 extracts.

DISCUSSION: Integrated metabolomics-bioactivity analysis identified citronellol and α-linolenic acid as candidate metabolites potentially associated with extract-mediated Escherichia coli reduction, while p-coumaric acid, citronellol, and α-linolenic acid showed positive associations with phage-enhanced antibacterial activity. These findings demonstrate that the antibacterial potential of Abutilon pannosum is season-dependent and support combining seasonal metabolomics, plant extract screening, and phage-extract strategies as an approach for identifying bioactive desert-plant metabolites against Escherichia coli O157:H7.