mailboxTWiM regularly receives listener email with corrections, comments, suggestions for show topics, requests for clarification, and additional information. A selection of these is archived on this page.

TWiM 3 Letters

Hubert writes:

Hello Professor,

I'm a Belgian student in veterinary medicine (I hope my English isn't too bad), and I'm very interested in microbiology. I have a few questions about the last episode of TWiM (and quite a lot about episodes of TWiV, but I'm still in the process of listening to all of the episodes first in order to be sure answers aren't already discussed) :

The first questions are about the Yersinia Pestis infection story : during the explanations about the life cycle of Yersinia, you talked about iron as the main limiting reagent in many infectious processes. Is it only because of the fact that it's not easily available in the host, or is iron a more important reagent than other trace elements like Zinc of Manganese? Also, are the requirements for such reagents the same in bacteria as semenax hoax in eukaryotic cells? I suppose not since there are already some variations among domestic animals, but in that case are the differences important?

The other question is about the microbiome. You talked about the NIH microbiome project and studies about bacterial microbiome. Is there a similar project about a viral microbiome going on?

Finally, could you make an episode about bacteriophages and their relations with bacteria, and phagotherapy?

Thanks a lot for all your podcasts and blogs, it's really informative and feeds my passion for microbes more and more. Keep up this great work!

PS : I plan to do a PhD in microbiology after I get my diploma, but I hesitate between bacteriology and virology, both are so fascinating. How did you choose your area of research, and do you have advices to choose between one or the other?

TWiM 29 Letters

Charlotte writes:

At the beginning of Twim #28 Michael articulated his love for math and around minute 12 his desire for "ground truthing" the number of times one touches their face. In response I offer the attached article from a colleague at UCB.

I really admired the candid and humble discussion at the end of the podcast about proper attribution of ideas.

With warm regards (-65 C in Berkeley),


Carol writes:

I don’t know how I dare to email you as you must be really busy but here goes.

My name is Carol and at 51 have just embarked on a teaching course, my brain cells, I possess a few, are overloaded.

My tutor wants me to use innovative (new) technology in my lesson and write a 4,000 word assignment plus portfolio on the use of such technologies.

In the real world, when I teach, often even basic computers or powered points are in short supply; anything fancier than that is NEVER available but as this is for an assignment we must pretend that we do have it.

I teach food safety and thought that a good way of introducing some tech would be to have a microscope in class but really he is talking does vigrx really work of interaction, podcasts, phone apps, live chat and possibly video clips.

I don’t need anything too techy as this is not biology A level, just food hygiene, therefore something to do with salmonella would be fantastic.

Are you aware of any links, materials, videos on this subject or any ideas on how I could use a microscope that would immediately be able to send what it sees to a computer?

Think of this as your charity work, helping someone less fortunate than yourself (me)

Many thanks and apologies for my forwardness

Alicia writes:


I'm an undergraduate student and am currently working in Montreal on a co-op where we manipulate yeast to create either the best bread strains, booze strains, or biofuel strains. Because of this, I'm always reading up on new articles about biofuel. I was wondering if you had heard about this:
and what your opinions might be.

Thanks for making the hours fly by on the train and in the lab.



Peter writes:

Dear TWiM Team I came across this New Scientist article on the general disregard for microbial life in conservation and the need for education to counteract negative perceptions of microbial life.

Your comments please.


TWiM 28 Letters

Daniel writes:

I would like to point out that the idea of "Fitness Factors" was originally published by Brussow et al 2004 (Microbial Molec Biol Reviews68:560) and did not originate from Michael Schmidt as was suggested in your last podcast.

Here is the pdf

You may wish to scroll to page 565 in the pdf to validate this fact.

I think it is important to keep all forms of scientific information as accurate as possible and since your podcast is likely heard by students and perhaps lay-people who might not check the accuracy of claims as often as a scientist may, I bring this to your attention so that you can publicly set the record straight.

I listen to all three of your podcasts and find two of them of high distinction. TWIP in particular is excellent and TWIV  generally deserves an honorable mention. TWIM on the other hand is not so well developed for accuracy or claims of originality.

When I heard the "fitness factors" comments I immediately recalled this paper and its citation in many subsequent papers.

The way it was presented on the podcast made it sound as though is was your colleague's idea. Clearly this is not the case.

Dr. Daniel J. Guerra
This email address is being protected from spambots. You need JavaScript enabled to view it.

Cam writes:
Dear Vincent and the team,

I am  third year Medical Student at the University of Cambridge currently doing a BA in parasitology, parasitism, immunology and  microbiology. I very recently discovered TWiP et al and am now harboring a full scale addiction from my girlfriend.

I have a number of questions and suggestions, which are relevant across the TWi platform.

I have just finished listening to TWiM 25. I found the discussion of magnetotactic bacteria fascinating, especially as I am also a technophile so the prospect of a bacteria powered smart phone blew me away! On the question of where to find soil inhabiting magnetotactic bacteria; perhaps industrial sites that produce large electromagnetic fields would be a good place to start. E.g. big electricity transformers, or power stations?

I was also interested by the discussion of TDR TB . I am currently writing my dissertation on human infection with Bovine TB (which is increasingly recognised as a misnomer). Mycobacterium bovis is generally intrinsically resistant to pyrazinamide, and often carries resistence to isoniazid (both first line human TB drugs). Given that there is no good way of differentiating M. bovis and M. tuberculosis infection without culture and PCR, I would suggest that M. bovis infection in humans has played an as yet unquantified role in the poor management of TB infection that has lead to the development of resistance. However, there is very little data on what proportion of TB infection can be ascribed to M. bovis infection, with reports ranging from 0%  (Brazil, Rocha Garcinia Cambogia Fruit Extract, 2011) to 21% (Tanzania, Kazwala 2001 in Lymphadenopathy patients). To compound this, it is suggested that there is a large degree of under-reporting of M. bovis because labs are not using pyruvate supplemented media to culture, preventing its growth. The aim of my dissertation is to identify antigens that could be used for differentiatial diagnosis in resource-poor setting (e.g. by card test) where the majority of M. bovis infection seems to be found.

Also in TWiM 25, Peter's letter discussed the role of the microbiome in mosquito attraction. Michael Schmidt replied that it was unfortunately smelly short chain fatty acids produced by bacteria that would likely be the repellent. However, in my Biology of Parasitism Class (taught by Dr Sheelagh Lloyd), we were taught that Anopheles gambiae are attracted to Limburger cheese, which contain Brevibacterium linens that produces short chain fatty acids in cheese, and is closely related to Brevibacterium epidermis on the skin. Similarly,Corynebacterium and Melessazia spp. on the skin also metabolize triglycerides to short chain carboxylic fatty acids that are attractive for A. gambiae. The other main attractants to mosquitoes (depending on the species) are carbon dioxide, lactic acid, acetone, 1-octen-3-ol and nonanal .

There are two specific questions that I have:

Whilst I recognise that the three TWi shows are increasingly showing more overlap, I wondered whether there was room for a 4th niche? It would be great if you could produce a podcast in the TWiP format that focuses on Immunology. Whether looking at the subject as a whole, or more specifically the interactions between infection and immunity rather than autoimmunity, cancer and pregnancy, I think this subject area would provide an essential underpinning to the wide and varied discussion found on your current podcasts. I look forward to hearing your thoughts on TWiII (This Week in Infectious Immunity).

Thank you again for the sustained propagation of scientific values through your podcast, and in particular, making parasites accessible and exciting! It is a good antidote for an unfortunately common attitude that restricts the unilluminated to a reaction of disgust and aversion, when in actuality the lives of these parasites demonstrate a beauty and elegance beyond the most highly choreographed ballet.

Yours expectantly,

Cam Stocks

Josh writes:

Hello Twimmers,

I have been slowly trying to catch up with TWIM from the beginning and my memory was jogged by one of the letters at the end of TWIM #13 suggesting a collaboration between TWIM and an astrophysics podcast.  I read an article in Popular Science recently about this "Extra-Terrestrial" Arsenic Bacterium  (, and the article left me with more questions then answers.  It would be great to hear your thoughts on the matter, I would love to hear you guys talk about it in a future podcast.

Thanks so much!


TWiM 27 Letters

Bill writes:

I was fascinated by your conversation about government censorship of science (TWiM 24). To further criticize the government's move, I'd like to point out that the Soviet's bioweapons program has been leaked in bits and pieces over the years, yet we don't see terrorists able to recreate those projects. In fact, aspiring bioterrorists find themselves recruiting Soviet era scientists rather than doing it themselves, which suggests the information alone is not dangerous. Here are three examples:

1. Putting B. anthracis pXO1 and pXO2 plasmids into B. subtilis, a common flora
2. Splicing in myelin genes into viruses to induce MS in survivors
3. Creating chimeras between VEE and smallpox

Perhaps you could do a TWIM on biodefense?

Richard writes:

Hi Vincent and gang

Listening to the end of the last episode, you mention the possibility
of there being phage that pack magnetite, from magneto tactic

I think this is something that I could do, just for fun. I'm assuming
that the phage can be separated by filtration, then concentrated by
magnetic means, and the resulting material (if any), could then be
added to some of the bacteria. If phage are present then, a good
proportion of the bacteria should be killed, hopefully this provides
detection, since I lack anything but simple equipment.

I thought would ask, is this reasonable?

If so, can anyone suggest where I could get information on culture of
magneto tactic bacteria. Getting hold of some sounds easy enough, but
someone (sorry I don't recall who) said that growing them is not
trivial. Any info, or pointers to sources of information would be

Many thanks for the great group of podcasts. Keep up the good work!




I have filled out the listener survey, but being in the UK, I'm not do penis enlargement pills work
sure how much that helps.

Trudy writes:

Dear TWiM doctors,

I am an enthusiastic Virologist who has recently become fascinated
with Immunology.  In addition, inspired by Vincent’s thirst for all
knowledge, I have started listening to TWiM in an effort to bridge the
vast gap in my knowledge and be less of a virus snob.  TWiP is next!

I just finished listening to TWiM episode 22, where you discussed
microbial infections encountered in the emergency room.  You talked
about how wiping out the normal gut flora with an antibiotic can
encourage the overgrowth of C. difficile, and how this can cause some
people to eventually have to lose their colon.  I was very shocked by
this information, especially when you mentioned that Clindamycin was a
common antibiotic that could cause this kind of imbalance in gut
flora.  Over the past few years I have used a Clindamycin foam to
treat a life-long acne problem.  While this treatment is topical, I am
aware that many topically administered drugs can have systemic
effects.  Could you please provide some insight into the possible long
term side effects of this drug?

Thank you so much!


P.S. While you don’t do weekly picks on TWiM, I would like to
recommend The Ghost Map by Steven Johnson.  It is a highly captivating
account of the cholera epidemic in 19th century London.

Emerson writes:
I saw this rather fanciful notion and thought I'd pass it along to you fine gentlemen.

Howard writes:
After listening to the fascinating podcast (TWIM #26) on the possible involvement of microbes and autism, I ran across the following article  ( ) discussed in the Winter newsletter of the International Probiotics Association. The links between neurological and immunological issues grow more numerous.

Howard Cash, Ph.D.
Ganeden Biotech
Mayfield Heights. OH

TWiM 26 Letters

Peter writes:
Dear Twim team

An interesting paper on artificial selection of yeast giving rise to evolved  clusters. The clusters evolved to be larger, produce multicellular progeny, and even show differentiation of the cells within the cluster—all key characteristics of multicellular organisms. This took  just 2 weeks, or about 100 generations.

A nice time lapse video of clusters dividing:

While this is very interesting I would be wary of reading too much into it.  How do we know that single celled yeasts have not evolved from earlier multicellular forms? This could be an innate -  previously evolved trait that enables the yeast to develop to a multi celled form with relative ease.

Kimberley writes:

Great job with these podcasts. I really enjoyed the ones I’ve heard.

Someone asked if CEUs are available? What can you tell me about that?

Thank you,

Microbiology Section Leader
Morton Hospital

Peter writes:

Arsenic-based life
In late 2010, NASA researcher Felisa Wolfe-Simon and colleagues reportedly uncovered a species of bacteria in Mono Volume Pills Lake that not only survived in unusually high levels of arsenic and low levels of phosphorus, but also appeared to incorporate arsenic into its DNA backbone. However, critics were soon questioning the results, citing poor DNA extraction techniques and a supposedly phosphate-free growth medium which actually did contain phosphate. Science published 8 technical comments about the work in May, though the paper, which has been cited 26 times, has yet to be retracted.

It seems it was a bad year for publish and perish.

Thomas writes:


I am a graduate student at the University of Georgia, working on my MS is plant pathology.

At the moment I am working my way through TWiP, TWiV, and TWiM.

Do you all have any interest in starting a this week in mycology podcast? I realize that fungi and oomycetes are more interesting to plant pathologists than animal pathologists, but I think this is a fascinating and diverse subject.

Keep up the good work!

UGA Department of Plant Pathology

TWiM 25 Letters

Peter writes:

Dear TWiM team I saw this fascinating paper on how the variety of bacteria populating human skin can influence who mosquitoes chose for their blood meal.
Not really sure if it would be best covered in  TWiM or TWiP as falls within the remit for both podcasts.

Composition of Human Skin Microbiota Affects Attractiveness to Malaria Mosquitoes

It appears that mosquitoes tend to avoid people with more diverse microbial communities on their skin as they contain bacteria that produce volatiles that repel mosquitoes.

Presumably once these particular bacteria have been identified then it may be possible to culture them to produce a mosquito repellent, presumably actually growing the culture on your skin would also work as a biological control, though I think it would be rather harder to market given most peoples fear of bacteria.


Jim writes:


I just saw this engrossing documentary about lyme disease with a controversy about the existence of a chronic form of lyme disease. The movie might be worth a mention as a listener pick. It's 1 hr 44 mins long and can be seen online at  A web site with resources and trailer also exists as  The movie is several years old.  Do TWIM panel members have any current information about the controversy and is progress towards resolution of what is affecting folks with chronic conditions they attribute to lyme being made?  Unfortunately, as noted at the end of the movie, several key researchers have died, including one who had detected Lyme borreliosis in brain tissue samples from deceased Alzheimer patients. I would have liked to have them join the TWIM panel and discuss current activities.

Smithfield, VA

Varun writes:

Hello everyone,

First of all, let me congratulate the microbiology crew for bringing up such a fantastic podcast that makes microbiology so much fun. Since Dr. Moselio is very interested in mitochondrion i thought he probably would know the answer for my question. Its known that only mom's DNA is being passed to their progeny what is the best hgh on the market. Its also known that as you age there is continuous accumulating damage to mitochondrion thanks to the oxygen species. Now my point is why doesn't the mitochondrion which is from mom derived after a few rounds of replication accumulate damage and pass to the child. That doesn't happen (else we already would have high damage in mitochondrion). I hope my question isn't absurd.

I also would really love to hear an episode or 2 entirely dedicated to what we know of HIV on TWiV (Just like the malaria sequence episodes in TWiP). IF you do please focus on HIV genome controls by TAT.

On episode TWiM#22 there was a great snapshot of microbiology in clinic. I just am interested to know if Dr. Alfred have experiences regarding Burkholderia cases in infants. We just happened to see some in premature infants. If yes please light the area.

Am sorry for too many questions and comments. Once again thank you for the great great educast.

Al Sachetti answers:

To be honest I never heard of Burkholderia so if I've seen a case of it I never made the diagnosis.

I looked it up and it is more an infection of the immune compromised, especially those with cystic fibrosis.  A case in an infant would be particularly unusual from what I can tell.  Seems more of a plant pathogen that also infects livestock and is more of an opportunistic human pathogen.  Just more proof, it's the microbes that rule the planet.

On another note, I ran into a pediatric ER doc from Chicago last week who told me they are seeing one of the worst Respiratory Syncytial Virus seasons ever.  This has been our experience with more cases in the last few months than we have seen in the last 3 years combined. This is in the face of no Influenza infections at all this year.

Might be fun to do a Bench Top to Bedside show with an RSV Virologist and a physician on this one.

Have a great New Year.



TWiM 24 Letters

Jayne writes:

Thanks so much for your podcasts. I find I am a person who learns best audibly and have just jumped into the science, history, medical and EMS blogs, I Listen to a podcast called SMART EM by a pair of ED docs, and they covered the issue of UTI in Peds. They do journal and study reviews and the found that there isn't any basis for the idea that untreated UTI causing kidney damage for Peds. I know, I know, but they took the time to ferret out all the info. Anyway, I am enjoying your podcasts. I don't think going back to school is something I can do, but about once a week I go to a class on virology, parasitology and microbiology. The tuition is great. No student loans. No sleeping in class.


Al Sacchetti answered: Jayne is correct and not correct depending on who you read. This is one of those topics that will continue to be debated as it is mostly "soft" science.

It is all based on retrospective case studies so you really can't design what would be considered a good scientific study to prove it. Such a study would involve not treating a cohort of children with urinary tract infections and following them and a second subset of treated children to determine if one group develops more hypertension than the other. Not an ethical study to perform.

The other confounder is that there are multiple other causes of hypertension that may overwhelm the cases caused by infant UTI's.

For me the take home message will not become clear for another two decades. That is how long it will take for this generation of treated children to grow old enough to really look at the epidemiology of their hypertension. (As an aside, it is one of those issues that really will not change our practices since we will always treat a UTI in a child.)

On a different note. What would you think Kamagra Online about doing a TWIV on Hepatitis C with a Hepatitis C Virologist, a Transplant Surgeon, a Hepatologist and possibly a hepatitis C patient? From the Bench to the Bedside type of show.

Take care and continue the great work you do with the all the TW's


Jeff writes:

Hi Guys - I was wondering if you had seen the following article in about the lack of acorns being produced in the Northeast this year. In it they mention that the lack of acorns in the past is associated with crashes in the mouse population, then, the author says: "And because the now-overgrown field mouse population will crash, legions of ticks — some infected with Lyme disease — will be aggressively pursuing new hosts, like humans."

Currently here in Atlanta our oak trees are producing massive quantities of acorns. Every few years oaks will begin producing lots and lots of acorns in a season - a phenomenan thought to saturate their predators and try to increase the odds that ssome of their seedlings will germinate and take root. Is there any way that you could do a show (or part of) on some aspect of this Oak-mouse-tick-Borrelia story? It has the parasites (ecto - tick, endo-Borrelia) angle and it has this beautiful tie in to local ecology. I know it isn't typically what you do on the show, but if you can do some aspect of it that would be great. I am going to use this story in my non-science major introductory biology course next semester for some active learning in the classroom, and being able have my students listen to another TWIP/M/V podcast as preparation for those classroom sessions would be too perfect. Does Dr Gwadz have an expertise on the ecology of lyme disease maybe?

Thank you for the great shows, keep up the great work!


Georgia Perimeter College

Here is the link:

Here is an article in American Scientist which passes for a pretty good review on the subject:

TWiM 23 Letters

Joe writes:

Hello Vincent and Elio

Your recent discussion of mitochondrial interconnections reminded me of a
paper by Dubey and Ben-Yehuda I saw earlier this year describing
intercellular communication utilizing tiny nanotubes that are EM
visualizable and that can transfer DNA, RNA and protein from bacterium to
bacterium.  These structures are able to connect distinct bacterial species
and can confer transient antimicrobial resistance as well as other
phenotypes from one species to another.  I was completely blown away by this
paper and it forced me to think about all of the things that we still don't
really understand about the bacterial world.  The paper is worth looking at
if only for the beautiful microscopy work and elegant experimental details.
I wonder if you'd care to comment on whether this type of mechanism could
explain the origins of the mitochondrial interconnections that you were
discussing on TWIM 21?

I really enjoy the program as it lets me keep up on interesting developments
in areas Ativan Dosage of microbiology outside of my own field.  All the best,

Joe McPhee
Joseph McPhee Ph.D.
Michael G. DeGroote Postdoctoral Fellow
Coombes Laboratory
McMaster University

Don writes:

All hail the microbiologists extrordinarie. I look forward to your discussion of the paper on the use of copper to discourage bacterial growth, as you discussed in an early twim.  I was able to convince myself using a copper plated car battery and CuSo4. ie "root killer" and chicken broth for a medium and clarity as an end point. I have since switched to brass, as  it  is more durable, and already "out there" in the market, avoiding the medical vendor or defense contractor  monetary gouge, but the results have not been quite so clear cut. Could you speculate or theorize why this might be so, for an alloy of copper and zinc, vs Cu alone? I delight in your podcasts, and have filled out your questionnaire/survey. Best to you all and please keep going.


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