Biofilm-Forming Endophytic Bacteria and Fungi from Bryophytes: Tools for Eco-Restoration of Polluted Habitats

Abstract

Bryophytes, including mosses and liverworts, are often the first plants to colonize nutrient-poor habitats and are known to support diverse microbial communities that enhance their ecological resilience. Although endophytic microorganisms have been extensively studied in vascular plants, comparatively few studies have examined bryophytes, particularly those inhabiting high-altitude ecosystems in India. In this study, we characterized culturable endophytic bacteria and fungi associated with seven bryophyte species collected from the Kumaon region of Uttarakhand, India. Isolates were assessed through morphological characterization (colony features, Gram staining, microscopic examination), biochemical assays (catalase, amylase, phosphate solubilization, indole-3-acetic acid production, 1-aminocyclopropane-1-carboxylate deaminase activities), and biofilm formation tests. Biofilm architecture was further visualized using scanning electron microscopy (SEM). A total of 31 endophytes (27 bacteria and 4 fungi) were isolated from the seven bryophyte species. Among the bacterial isolates, 64.5% were Gram-negative and 76% exhibited bacillary morphology. Nearly all isolates (97%) produced indole-3-acetic acid, 48.8% displayed 1-aminocyclopropane-1-carboxylate deaminase activities and 77.24% formed biofilms. Five of the most promising isolates possessed five or more plant growth-promoting (PGP) traits. Electron micrographs revealed dense bacterial monolayers and intricate three-dimensional architectures in which fungal hyphae served as structural scaffolds. These results demonstrate that Kumaon bryophytes host taxonomically diverse, metabolically versatile and structurally interactive endophytic assemblages with pronounced plant-growth-promoting potential, offering novel candidates for stress-resilient bio-inoculants and expanding current understanding of plant-microbe relationships in extreme environments. The documentation of fungus-mediated bacterial scaffolding within bryophyte biofilms constitutes a previously unrecognized ecological strategy.