#thallus — the body of a lichen, built from distinct layers of symbionts, such as fungus or alga, that does not resemble the shape of any one partner in isolation
#axenic — a culture containing only one organism, free from others. You can think of it as "clean" or "pure"
The image is a meme, represented by a comic parody of the Trojan Horse. A large wooden horse labelled “Lichen tissue fragment” is being pulled toward a castle gate marked “Axenic resynthesis” by person labelled “Tissue culture method.” They say, trying to convince the gatekeepers: “The best part is: it’s completely clean of algae!” Inside the horse, the hidden compartment is labelled “Resident lichen microbiota.” The cartoon humorously illustrates how supposedly sterile lichen cultures can still harbour visually undetectable microbial communities.
Then came what we affectionately call terrarium lichens: thalli ground up, filtered, sorted into “algal” and “fungal” pieces, then coaxed back together. The Tissue Culture method yielded impressive, yet unlikely #axenic structures, as resident #microbiota were never methodologically addressed. 5/8
Defining #axenic was equally ambiguous. For much of the 20th century, spore discharge was believed to yield #sterile cultures, even as bacterial #contamination was regularly noted. Without antibiotics or molecular checks, ‘axenic’ was mostly assumed—or confirmed visually. 3/8
