The symbiotic interaction between fungus and algae, which science has mostly ignored up until now, has been detailed by researchers from the Institute of Botany, Czech Academy of Sciences. Alcobiosis is a novel term describing the coexistence of algae and corticioid basidiomycetes, which are widespread in temperate woods. Scientific Reports has published their study.
The study’s lead author, Jan Vondrák of the Institute of Botany’s Department of Taxonomy, explains that when some of the fungal coatings on wood or bark (known as corticioid fungus) are disturbed, they would often be surprised to discover a layer of green algae. Because the fungus does not rely on the algae for nutrition, they learned that this is a symbiotic relationship of fungi and algae rather than a lichen.
The letters from the three terms, algae, corticioid fungus, and symbiosis, are combined to form the new name “alcobiosis” that the researchers have coined for this kind of coexisting.
The study team collected several samples over the course of several years and sequenced the DNA of the fungal and algal partners. They found that the symbiosis is quite prevalent and may be found in a wide variety of corticioid fungus within the class of agaricomycetes. A particular algal species among a variety of algae documented in diverse alcobioses is typically faithfully matched by a single fungus species.
Algal activity in alcobioses was monitored physiologically, and the results showed that the algae are alive, active, and highly involved in photosynthesis, which demonstrates that they thrive inside fungal tissue. Alcobioses resemble lichens in appearance, but they vary from them in that the fungal partner does not rely on the alga for nutrition.
The fundamental question that remains is how this symbiosis benefits each of the partners. The discovery also raises a number of issues about the geographic, ecological, and taxonomic aspects of the symbiosis, such as whether the variety of alcobioses rises from arctic to tropical locations.
This coexistence has already been discussed in articles. The majority of the time, however, these were only vague remarks stating that some corticioid fungus species frequently coexist with algae. This research was the first to recognize alcobioses as a widespread phenomenon involving several fungus and algae.
The researchers also found that tiny gastropods, which frequently consume corticioid fungi, contribute to the spread of alcobioses. Their excretions include living algae and fungal cells, which quickly produce fresh alcobiotic covering. This form of reproduction resembles lichen “isidia.”
The Institute of Botany’s scientists have described a symbiotic connection that is fairly prevalent in Europe but has received little attention up to this point. As alcobioses are readily apparent to the unaided eye and can be easily distinguished from related fungi that do not establish this sort of interaction, a new area has opened up for the further research of alcobioses from numerous points of view by both professional biologists and biology amateurs.
Jan Vondrák et al, Alcobiosis, an algal-fungal association on the threshold of lichenisation, Scientific Reports (2023). DOI: 10.1038/s41598-023-29384-4. www.nature.com/articles/s41598-023-29384-4