Heather writes:

Dear TWIMians,

A great episode (as always). Regarding the letter discussed at the end, on poisonous mushrooms (or, rather, regarding the following talk), I can maybe add a (very) little. Elio is quite right that mycologists have been discussing the “Why” of mushroom poisons forever, and with very little in the way of a solid answer. Regarding the deadliest known mushroom poisons, amatoxins, these are produced by mushrooms in four unrelated genera, and act by binding tightly (though not quite irreversibly) to eukaryotic RNA polymerase II, halting transcription and, ultimately, protein synthesis. They are actually not effective against bacterial RNA polymerases and, in eukaryotes, are more effective against mammals than insects, against insects than plants, against plants than some single-celled organisms like trypanosomes (which are unaffected by alpha-amanitin and other amatoxins). As discussed, this is not likely to have been selected as a defense compound against humans or mammals, due to the delay in symptom development. Two possibilities are that amanitin is protecting against insect larvae (Drosophila is susceptible to amatoxin poisoning, but resistant Drosophila with mutations in the amatoxin-binding residues of RNA polymerase II have been selected in culture), or against mycoparasites (Hypomyces hyalinus parasitizes edible Amanita mushrooms in the section Validae, but has not been found parasitizing mushrooms in the amatoxin-producing sister section Phalloideae) – so, it might be effective against low motility organisms living in close contact with the mushrooms over prolonged time.

Best regards,


Heather Hallen-Adams, Ph.D.
Assistant Professor of Practice
Food Science and Technology
University of Nebraska-Lincoln

Hibiscus writes:

Hello Vincent and Co.,

I am a microbiology student in Southern California. The weather is starting to give us need for electric blankets and heaters at night, being between 70 – 49 °F (22 – 9 °C), extremely cold for natives of sunny California who think of snow as a legend. I have been listening to both TwiM and TwiV on and off for a year or so, and appreciate all what I have learned about viruses and microbes. Your discussions are very entertaining and insightful, and my study sessions are that much more enjoyable.

My first introduction to Microbiology was through a manga, or Japanese comic, called Moyashimon. This manga is about the shenanigans people at agricultural university get up to, but the interesting part is the main character who can see microbes without a microscope! While reading, I found out that one of my favorite authors was a microbiologist. Beatrix Potter, the creator of Peter Rabbit and Jemima Puddle duck! I was wondering how often her paper was discussed in Microbiology classes, or whether she has been lost to obscurity.

Thank you for reading,