Scientists are exploring different avenues to combat infectious diseases caused by both bacterial and fungal pathogens, for which the inhibition of biofilm formation is one of the most promising leads. Abraham and Estrela (2016) reported that fungal metabolites are becoming increasingly explored for their potential to inhibit the formation of biofilms, e.g. by interfering with quorum sensing, and some compounds have already been discovered that can even destroy pre-formed biofilms. A recent example is coprinuslactone (11) (de Carvalho et al. 2016), a small molecule derived from the edible mushroom Coprinus comatus, which acts against Pseudomonas aeruginosa biofilms. Other examples include roussoellenic acid (12) from a Roussoella sp. (Phukhamsakda et al. 2018), which is active against biofilm formation in Staphylococcus aureus, as well as microporenic acid A (13) from a Kenyan basidiomycete (Chepkirui et al. 2018; Fig. 4), which can not only inhibit biofilm formation in both Staphlococcus aureus and the human pathogenic yeast, Candida albicans, but even destroys pre-formed biofilm in C. albicans at rather low concentrations. These compounds do not have prominent antimicrobial activities and therefore their application is unlikely to raise resistance. The biofilm inhibitors are very promising candidates for use in combination therapy with antibiotics. In several studies, biofilm inhibitors were shown to enhance the activity of the antibiotics by increasing their ability to penetrate the biofilms.
These examples illustrate that fungi are under-explored with respect to novel antibiotics and other therapeutic agents, and that it is certainly worthwhile to expend more effort in this area of research with an emphasis on hitherto neglected species from regions and habitats that have not yet been studied systematically. Fungi have much to offer in terms of novel chemistry: due to the advent of revolutionary techniques in genomics, transcriptomics, bioinformatics, analytical chemistry and biotechnological process development, we can now explore the chemical diversity of the mycobiota much more concisely than ever before. Evidence is also accumulating that novel phylogenetic lineages or hitherto neglected taxonomic and ecological groups of fungi can now much more easily be recognized and subjected to the exploitation of their secondary metabolome. However, more public funding is needed to assure that the substantial know-how that has been acquired over many decades does not become forgotten, and that the next generation of researchers will also still be able to work on novel, hitherto unexplored fungal groups, rather than only on model organisms.