🍄 From Onion Peel to Mycelium: How a Kitchen Mishap Cracked Open the World of Fungi

Sailekshmi · August 22, 2026, 4:53pm

CUBE Chatshaala – Discussion Summary

The August 22, 2026 session of CUBE Chatshaala opened with a familiar, everyday observation: an onion left sitting in the kitchen that had developed small black spots on its surface. Rather than dismissing this as ordinary spoilage, the discussion used it as a doorway into microbiology, asking what those spots actually are and why they appear.

The participants identified the black spots as a colony of fungus, more specifically black mold. From there, the conversation moved into taxonomy, using the mold as a worked example of scientific naming. The genus and species were written out as Aspergillus niger, with the whiteboard explicitly separating the genus (Aspergillus) from the species (niger) to reinforce how binomial nomenclature works in practice a small but important habit-forming exercise for students still getting comfortable with biological classification.

The session then widened the lens from mold to fungus as a broader category, using mushrooms as the more visually familiar example. A slice of bread was used as a second everyday substrate to illustrate that fungal colonies aren’t unique to onions; they show up wherever the right moisture and organic material are present, whether that’s a kitchen vegetable or a piece of bread going stale on the counter.

A particularly interesting branch of the discussion involved mycelium, the thread-like network mushrooms and other fungi use to draw nutrients from soil or decaying wood. The whiteboard sketch showed mushrooms sprouting from a log with mycelium spreading underground, visually tying together the fungal life cycle: the mycelium as the “hidden” working body of the organism, and the mushroom as merely the visible fruiting structure.

The session closed on an open question, marked with a large red question mark, connecting the mushroom-and-mycelium diagram back up to microbiology as a discipline. This appears to have been left deliberately unresolved, likely an invitation for participants to think through, in their own time, how the visible macro-scale organism (mushroom) relates back to the microscopic world that microbiology studies, or to prompt discussion on log/wood decomposition in the next session.

Present for the discussion included Niharika Baghari, MS Sailekshmi, Arunan MC, Susanta Tanti, Kiran Varma, Aarya Takke, Chitralekha, and Himanshu Joshi.

Provocative Questions

If mold and mushrooms are both fungi, why does one look like a stain and the other looks like a plant? What does that tell us about how fungi grow differently depending on their environment?
The mycelium was drawn as an unseen network beneath the mushroom. Could something similar exist in the onion sample: a hidden structure driving the visible black spots we see on the surface?
Why do scientists insist on two-part names like Aspergillus niger instead of just calling it “black mold”? What would be lost if we only used common names?
The bread slice and the onion both grew fungus under different conditions. What variables (moisture, temperature, exposure to air) might explain why fungi appear on some foods faster than others?
The session ended with a question mark linking mushrooms back to microbiology. What do you think that connection is supposed to be, and where does the “micro” in microbiology actually apply to something as large as a mushroom?

What I Have Learned

Today’s session was a good reminder that microbiology doesn’t need a laboratory to begin; it can start with something as mundane as a forgotten onion in the kitchen. What struck me most was how naturally the discussion moved from a casual household observation to formal scientific vocabulary, without that transition feeling forced. Learning to name Aspergillus niger properly, with genus and species clearly separated, made the abstract idea of binomial nomenclature feel concrete rather than something to memorize.

I also came away with a clearer mental picture of the relationship between mold, mushrooms, and fungi as a whole. Before this session, I hadn’t thought carefully about mycelium as the actual “body” of many fungi, with the mushroom being just the reproductive, visible part. That reframing changes how I look at fungal growth generally; the part we see is often only a small piece of a much larger, hidden network.

Finally, the way the session ended on an open question rather than a tidy conclusion was itself a useful lesson. Not every scientific discussion needs to be neatly resolved; sometimes the most valuable outcome is a sharper question to carry into the next session.

TINKE Moments (This I Never Knew Earlier)

Naming conventions matter more than they first appear. Writing “genus” under Aspergillus and “species” under niger on the board made it click that scientific names aren’t arbitrary labels; they follow a strict, hierarchical structure that every organism on Earth is meant to fit into.
A single household object can anchor an entire lesson. Using the onion as the starting point, rather than a textbook diagram, made the abstract idea of fungal colonization far more tangible and personally relatable.
The mushroom is not the whole organism. The mycelium sketch was a genuine “aha” moment, realizing that what we call a mushroom is really just the fruiting body, while the actual living network extends invisibly through soil or wood, reframes how fungi should be thought about biologically.
Common food spoilage connects directly to formal taxonomy. Bridging “black mold on an onion” to “Aspergillus niger, genus and species” in one continuous thread shows how quickly informal observation can be formalized into scientific language, which is a useful model for approaching other everyday phenomena.

Gaps and Misconceptions

The session did not clarify why the specific species Aspergillus niger was chosen as the example; was this confirmed through actual identification of the onion mold, or used as a generalized illustrative example of black mold? This distinction matters for scientific accuracy and could confuse participants into assuming all black mold is automatically Aspergillus niger.
The connecting question mark between the mushroom/mycelium diagram and “Microbiology” was left open without any framing or hint, which may leave participants uncertain about what specific concept they are meant to arrive at; some scaffolding or a follow-up prompt would help avoid this becoming a genuinely unanswered gap rather than a productive one.
There’s an implicit assumption that “black spots on an onion” and “mold on bread” are caused by the same or similar fungal agents; this was not explicitly verified or contrasted, and different substrates often host different fungal species, which is worth clarifying in a future session.
The jump from mold (microscopic-scale colony) to mushroom (macroscopic fruiting body) as parallel examples of “fungus” is scientifically valid, but the session didn’t explicitly address the vast differences in scale, complexity, and lifecycle between microscopic molds and larger basidiomycete fungi like mushrooms a nuance that could be misunderstood as “all fungi are basically similar.”

Photographs during Chatshaala