Melissa writes:

Hi TWIMmers,

I recall Elio mentioning in a past podcast a that there were human lab members who had drank E. coli K12.  Do you happen to have the reference for this? My colleagues and I are really interested to read about how this idea came about.  Was this mentioned in “The Recombinant DNA Controversy” book that is in Elio’s web page above?

Thank you,


Josep writes:

Hello everyone from TWiM. Hope you all are having a pleasant day.

My name is Josep Jorente, I’m a graduate on Medicine and Health Sciences from a small university in Marília, countryside of São Paulo state, Brazil.

I am very passionate about science, and specially micro and molecular biology, so as a newcomer of the show, I must say you made my moments off extremely happy.

On the last episode, more ever, I got very excited.

Fan mail aside, I wanted to compliment Michelle when she asked how the napoleon worm-bug symbiosis started, because I had myself this question when you started the snippet. Maybe there is a specific location for the worm to procreate, and the habitat where its early life develops is associated with bug contact.

Also, when Vincent joked about who’s in charge, I remembered this magnificent excerpt from Yuval N. Harari’s Sapiens on “was wheat or us in charge of the agricultural revolution?”. Which begged the thought in my mind “It is well known the importance of the enteric nervous system on physiology and behavior of the human. Now how much of it is controlled by gut bugs?”

Anyways, thank you very much for your work, please continue.

Best regards,


Karen writes:

Dear TWIM team,

Thank you for presenting the absolutely fascinating story of the flatworm Paracatenula and its chemosynthetic symbiont. Mind expanding!

There was one point that needs clearing up. At 21:09 the question was asked as to whether the endosymbionts are vertically transmitted. The paper gives the answer: “Each species of Paracatenula harbors a specific Ca. Riegeria, and the endosymbionts have been vertically transmitted for at least 500 million years. Such prolonged strict vertical transmission leads to streamlining of symbiont genomes, and the retained physiological capacities reveal the functions the symbionts provide to their hosts.” (My comment: 500 million years! That is way back in the history of animal life.)

A paper that describes the reproduction of Paracatenula provides an understanding of how this vertical transmission occurs. “Most catenulids…predominantly reproduce by a type of asexual fission termed paratomy, during which new clonal worms grow from the posterior end of the animal, thus generating a chain of zooids (the Latin word “catenula” means “small chain”). The zooids subsequently develop into separate individuals and detach from the mother zooid. Sexual reproduction is rarely observed in catenulids and has never been observed in Paracatenula.” The paper provides evidence that when the zooids form they contain bacteriocyte cells the house the endosymbionts.

Mark writes:

Hello Vincent,

You seem to be an enthusiastic supporter of vaccination, and I agree with you.  But how to best influence reluctant parents remains an issue.

There was a letter in the Wall Street Journal a few days ago that I thought you might find interesting:  “The Complicated Truth About Vaccines“.  Dr. Michael Segal writes that “They [vaccines] can appear to be the proximate cause of a condition when they have nothing to do with the ultimate cause.”

The letter focuses on a 2010 study published in The Lancet that “aimed to establish whether the apparent association of Dravet syndrome with vaccination was caused by recall bias and, if not, whether vaccination affected the onset or outcome of the disorder” and finds, in Dr. Segal’s words, that “vaccines did trigger the deterioration—but had the children not been vaccinated, the same deterioration would have occurred anyway the next time they had a cold.

Dr Segal summarizes the study “by studying the detailed time course in a genetically characterized population, they illustrated how vaccines can appear to be the proximate cause of an injury, yet the ultimate cause is genetic.” and concludes that “Unless we act like scientists and explain the science, we won’t be effective in helping laymen put the [frequently reported vaccination horror] anecdotes in context.

All the best,