Efficacy of propidium iodide and FUN-1 stains for assessing viability in basidiospores of Rhizopogon roseolus

The Concentration-Dependent Effects of Essential Oils on the Growth of Fusarium graminearum and Mycotoxins Biosynthesis in Wheat and Maize Grain

The presence of Fusarium fungi and their toxic metabolites in agricultural crops contributes to significant quantitative and qualitative losses of crops, causing a direct threat to human and animal health and life. Modern strategies for reducing the level of fungi and mycotoxins in the food chain tend to rely on natural methods, including plant substances. Essential oils (EOs), due to their complex chemical composition, show high biological activity, including fungistatic properties, which means that they exhibit high potential as a biological plant protection factor. The aim of this study was to determine the fungistatic activity of three EOs against F. graminearum, and the reduction of mycotoxin biosynthesis in corn and wheat grain. All tested EOs effectively suppressed the growth of F. graminearum in concentrations of 5% and 10%. Cinnamon and verbena EOs also effectively reduced the ergosterol (ERG) content in both grains at the concentration of 1%, while at the 0.1% EO concentration, the reduction in the ERG amount depended on the EO type as well as on the grain. The degree of zearalenone (ZEA) reduction was consistent with the inhibition of ERG biosynthesis, while the reduction in deoxynivalenol (DON) was not consistent with this parameter.

Antifungal Activity of Siderophore Isolated From Escherichia coli Against Aspergillus nidulans via Iron-Mediated Oxidative Stress

Microorganisms produce various secondary metabolites for growth and survival. During iron stress, they produce secondary metabolites termed siderophores. In the current investigation, antifungal activity of catecholate siderophore produced by Escherichia coli has been assessed against Aspergillus nidulans. Exogenous application of the bacterial siderophore to fungal cultures resulted in decreased colony size, increased filament length, and changes in hyphal branching pattern. Growth inhibition was accompanied with increased intracellular iron content. Scanning electron microscopy revealed dose-dependent alteration in fungal morphology. Fluorescent staining by propidium iodide revealed cell death in concert with growth inhibition with increasing siderophore concentration. Antioxidative enzyme activity was also compromised with significant increase in catalase activity and decrease in ascorbate peroxidase activity. Siderophore-treated cultures showed increased accumulation of reactive oxygen species as observed by fluorescence microscopy and enhanced membrane damage in terms of malondialdehyde content. Antifungal property might thus be attributed to xenosiderophore-mediated iron uptake leading to cell death. STRING analysis showed interaction of MirB (involved in transport of hydroxamate siderophore) and MirA (involved in transport of catecholate siderophore), confirming the possibility of uptake of iron-xenosiderophore complex through fungal transporters. MirA structure was modeled and validated with 95% residues occurring in the allowed region. In silico analysis revealed MirA-Enterobactin-Fe³⁺ complex formation. Thus, the present study reveals a promising antifungal agent in the form of catecholate siderophore and supports involvement of MirA fungal receptors in xenosiderophore uptake.

Discovering the role of Patagonian birds in the dispersal of truffles and other mycorrhizal fungi

Dispersal is a key process that impacts population dynamics and structures biotic communities. Dispersal limitation influences the assembly of plant and microbial communities, including mycorrhizal fungi and their plant hosts. Mycorrhizal fungi play key ecological roles in forests by feeding nutrients to plants in exchange for sugars, so the dispersal of mycorrhizal fungi spores actively shapes plant communities. Although many fungi rely on wind for spore dispersal, some fungi have lost the ability to shoot their spores into the air and instead produce enclosed belowground fruiting bodies (truffles) that rely on animals for dispersal. The role of mammals in fungal spore dispersal is well documented, but the relevance of birds as dispersal agents of fungi has been understudied, despite the prominence of birds as seed dispersal vectors. Here, we use metagenomics and epifluorescence microscopy to demonstrate that two common, widespread, and endemic Patagonian birds, chucao tapaculos (Scelorchilus rubecula) and black-throated huet-huets (Pteroptochos tarnii), regularly consume mycorrhizal fungi and disperse viable spores via mycophagy. Our metagenomic analysis indicates that these birds routinely consume diverse mycorrhizal fungi, including many truffles, that are symbiotically associated with Nothofagaceae trees that dominate Patagonian forests. Epifluorescence microscopy of fecal samples confirmed that the birds dispersed copious viable spores from truffles and other mycorrhizal fungi. We show that fungi are a common food for both bird species and that this animal-fungi symbiosis is widespread and ecologically important in Patagonia. Our findings indicate that birds may also act as cryptic but critical fungal dispersal agents in other ecosystems.