Reviewing the taxonomy of Podaxis: Opportunities for understanding extreme fungal lifestyles

Current Biological Knowledge, Applications, and Potential Use of the Desert Shaggy Mane Mushroom Podaxis pistillaris (Agaricomycetes): A Review

Podaxis pistillaris, an abundant gasteroid mushroom, has become an important biological element in arid and semiarid communities worldwide. This mushroom possesses cosmetic, edible, and medicinal attributes, playing a crucial role in communities in countries such as Australia, India, Saudi Arabia, Yemen, and Mexico. Proximate studies highlight the nutritional richness of P. pistillaris, characterized by high protein content and essential bioelements such as K, P, and Mg. Furthermore, P. pistillaris is integral to the traditional medicine of indigenous communities in America, Asia, and Africa, where it is revered for its purported wound-healing, anti-inflammatory, and coagulant properties. In the case of Mexico, the Seri community uses and markets P. pistillaris in various forms, including ointments and, within the region, its spores. Chemical analysis of this species reveals notable compounds, including epicorazines A-C exhibiting antimicrobial properties, along with polysaccharides such as β-glucans, and a recently identified ergosterol derivative named podaxisterol. Despite its importance, the chemical characterization and assessment of the biological activity of its compounds have been largely understudied. Consequently, there are currently no wound-healing products on the market derived from fungi, as the majority originate from plant sources. This work aims to present the essential aspects of P. pistillaris's ethnobiological use, medicinal properties, bioactive compounds, and biotechnological applications. In addition, it underscores the overlooked status of P. pistillaris among fungi inhabiting arid areas, emphasizing its potential as a valuable subject for further research.

Insights into the Metabolomic Capacity of Podaxis and Isolation of Podaxisterols A-D, Ergosterol Derivatives Carrying Nitrosyl Cyanide-Derived Modifications

Cultures of a termite-associated and a free-living member of the fungal genus Podaxis, revived from spores maintained in century-old herbarium collections, were analyzed for their insecticidal and antimicrobial effects. Their secondary metabolomes were explored to uncover possible adaptive mechanisms of termite association, and dereplication of LC-HRMS/MS data sets led to the isolation of podaxisterols A-D (1-4), modified ergosterol derivatives that result from a Diels-Alder reaction with endogenous nitrosyl cyanide. Chemical structures were determined based on HRMS/MS and NMR analyses as well as X-ray crystallography. The putative origin of the endogenous fungal nitrosyl cyanide and ergosterol derivatives is discussed based on results obtained from stable isotope experiments and in silico analysis. Our "omics"-driven analysis of this underexplored yet worldwide distributed fungal genus builds a foundation for studies on a potential metabolic adaptations to diverse lifestyles.

Studying Soil Ecology and Growth Conditions of Phellorinia herculeana, a Wild Edible Mushroom

Phellorinia herculeana is an edible mushroom growing in nutritionally poor and desert soil. There has been little information available about its edaphic and culturing conditions for achieving the vigorous mycelial growth essential for its artificial cultivation, bioaugmentation and biodegradation in unfertile soil. Thus, the present study was conducted to assess its edaphic conditions and find a suitable culturing medium for obtaining maximum growth. It grows commonly in coastal soil with saline conditions, barren land soil unfit for cultivation, and desert soil. It forms a basidiocarp singly around xerophytic trees and annual plants and also in soil without vegetation. In addition to a well-developed pileus and stipe, it has a typical rhizoid that grows horizontally in soil. The rhizoid was thick at the base of the stipe and became thin into the mycelial strand. In our earlier study, we reported that its mycelial growth was very poor on nutrient-rich media containing simple sugar, for example, glucose. In the present study, we observed that cereal-grain-based agar media supported its mycelial growth and among the cereal-grain-based agar media, maize agar medium at the 5% level supported the maximum mycelial growth. Incorporation of glucose into the maize agar medium reduced its mycelial growth compared to its growth on maize agar medium without glucose. Its mycelial growth was at a maximum between 34 °C and 37 °C and at a pH between 7 and 8. Mass multiplication using sand-maize medium prepared at the ratio of 19:1 (sand: maize) supported the maximum mycelial growth. The results of this study would certainly pave a way for the scientific community to develop a protocol for its artificial cultivation and also for its mass multiplication, bioaugmentation and biodegradation in unfertile soil.

Genome reduction and relaxed selection is associated with the transition to symbiosis in the basidiomycete genus Podaxis

Insights into the genomic consequences of symbiosis for basidiomycete fungi associated with social insects remain sparse. Capitalizing on viability of spores from centuries-old herbarium specimens of free-living, facultative, and specialist termite-associated Podaxis fungi, we obtained genomes of 10 specimens, including two type species described by Linnaeus >240 years ago. We document that the transition to termite association was accompanied by significant reductions in genome size and gene content, accelerated evolution in protein-coding genes, and reduced functional capacities for oxidative stress responses and lignin degradation. Functional testing confirmed that termite specialists perform worse under oxidative stress, while all lineages retained some capacity to cleave lignin. Mitochondrial genomes of termite associates were significantly larger; possibly driven by smaller population sizes or reduced competition, supported by apparent loss of certain biosynthetic gene clusters. Our findings point to relaxed selection that mirrors genome traits observed among obligate endosymbiotic bacteria of many insects.

A first checklist of macrofungi for South Africa

Macrofungi are considered as organisms that form large fruiting bodies above or below the ground that are visible without the aid of a microscope. These fungi include most basidiomycetes and a small number of ascomycetes. Macrofungi have different ecological roles and uses, where some are edible, medicinal, poisonous, decomposers, saprotrophs, predators and pathogens, and they are often used for innovative biotechnological, medicinal and ecological applications. However, comprehensive checklists, and compilations on the diversity and distribution of mushrooms are lacking for South Africa, which makes regulation, conservation and inclusion in national biodiversity initiatives difficult. In this review, we compiled a checklist of macrofungi for the first time (excluding lichens). Data were compiled based on available literature in journals, books and fungorium records from the National Collection of Fungi. Even if the list is not complete due to numerous unreported species present in South Africa, it still represents an overview of the current knowledge of the macromycetes of South Africa. The list of names enables the assessment of gaps in collections and knowledge on the fungal biodiversity of South Africa, and downstream applications such as defining residency status of species. It provides a foundation for new names to be added in future towards developing a list that will be as complete as possible, and that can be used by a wide audience including scientists, authorities and the public.