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 49 Letters

Robin writes:

The matriarch of a hunter-gatherer band might prefer males to be assigned to specialised training in hunting skills. So the subconscious bias probably goes back a couple of million years to the early days of Homo before sapiens.

Chip writes:

Saw this paper in my inbox this morning and thought It might be a good fun discussion paper on an upcoming TWiM episode!


Meimei writes:

Dear Dr Racaniello,

I do not have the talent for a M.D-Ph.D. at Columbia, but I am madonna pokies definitely a huge fan:)

It's striking how and where the interaction of antibody and bacterium occurs (TWIM #48)! Learned a lot from listening to your interpretation of the paper. Many Thanks!
Just have a question about one antibody and one bacterium. Is it commonly considered more than one antibody molecule per bacterium?

Many Thanks, again!

P.S. Can this finding extent to the interaction between virus (e.g. HIV) and neutralizing antibody? It might be we just look at the wrong place for all those years!

TWiM 48 Letters

Sierra writes:

Hello Racaniello et al.,

I am a plant pathologist for a vegetable seed company in Washington state.  I listen to TWIM, TWIP and TWIV podcast while I read extensive disease resistance screens.  I started out studying microbiology as an undergrad and discovered plant pathology that allows me to study microbes and plants together.  Listening to these podcasts keeps my mind engaged while looking at thousands of potentially disease baby plants.  I really appreciate what you all do to put together such intellectually stimulating topics.

If I may suggest a topic as well.  Iron sequestration and uptake in bacteria is very fascinating and affects many aspects of bacterial life.  I may be biased as I worked on iron uptake during my Ph.D. I have listened to many of the TWIM podcasts and iron pops up in discussion now and then.  It would be nice to listen to a discussion of this topic from your perspective.

Keep up the good work,


Eric writes:

Dear Twim:

Episode 2 had a career inquiry from a listener.  The listener was considering additional graduate work Pokies, but was not sure which way to go or whether to invest the required time and energy in an MBA or Ph.D.

May I suggest intellectual property as a career path?  Most patent attorneys are former "lab rats."  Patent attorneys enjoy a good salary and interaction with some very intelligent and interesting people.  Though considerable work is required, intellectual property can be a very rewarding career.

Best regards,


Patent Attorney

Flagstaff, AZ

Ori writes:

Hello all!!

Quick follow-up from Twim 47. 

It seems that many bacteria have means to take up foreign DNA and integrate it Into their own chromosomes. This definitely can provide a selective advantage depending on the nucleic acids being taken up. On the other hand, transferring your own DNA to another cell seems to be quite unselfish. For example, if I had some form of an antibiotic resistance gene, why would I give it away to others that would, in the end, compete with me for nutrients? In essence, what is the selective advantage for giving away nucleic acids?

Thanks a lot and have a happy holiday!

TWiM 47 Letters

Maureen writes:

I love all your series (TWIM,TWIV, and TWIP) and learn immensely from them. I am a Clinical Research Nurse and work at NIH in the National Institute of Allergy and Infectious Disease (NIAID) unit that houses the KPCR  patients that you may have recently read about.

I'd like to hear a discussion about this isolate as you educate everyone so thoroughly. Our hospital has worked diligently to track and eliminate this organism from our hospital and we've just about succeeded but I'd still like to be better informed about KPCR. Thanks.

P.S. Please Please Please start a TWIB!! We work with so much that I still need to be educated about various bacteria.

Thanks immensely for all the education you give us.

Jim writes:

Hi Vincent and Friends,

Thank you very much for the informative and often imaginative discussions that take place in TWiM. It's a real pleasure to listen to such a quality, fun, easily accessible (and free!) source of microbial material. I'm sure you are often thanked for taking the effort to put it out there, but I wanted to add my voice. As a cell and molecular biology student it offers some wonderful connections and points of interest to my education.

My question relates to a recently published book by Trudy M. Wassenaar that I have been reading, titled "Bacteria: The Benign, the Bad, and the Beautiful." Has anyone read this book, and if so what are their thoughts on it? I would recommend it to those with a broad interest, or who need an introduction, like students such Pokies as myself. It offers an incredibly interesting and diverse description of bacteria and is easy to understand. I actually picked it up because it was recommended by the google+ "Microbiology" account (

Thanks again, and warm regards.

Steve writes:

TWiM Audio File with Interactive Transcription

Here is a link to a partial, video I created from the TWiM 06 audio file: I created a video file from the audio file so that I could use the YouTube captioning tool to import an interactive transcript -- minutes five (5) through twelve (12). I created the time-coded transcript using an online tool called Subtitle-Horse, (

If you click the interactive transcript button on the button-bar (Like, Dislike, Add to, etc) just below the video player, you can see how the transcript works. The transcript is indexed, time coded to the audio.

Potential Benefit of Interactive Transcription

The time-coded transcript text could be parsed and placed in a database for easy query. Then all included audio/video files are text searchable and associated to the segment of the source audio/video clip.

Collaborative Transcription

On TWiV a number of people have completed or are working on transcripts. In my experience, transcription is a time intensive process. To lighten individual time commitment, it would be nice to get several people to work collaboratively to transcribe one TWiV audio/video. Although far from perfect, the subtitle-horse online transcription tool could be used for this.

Volunteer to Help Transcribe

As a first step, if interested, I’d be interested in coordinating a collaborative transcription of a TWiV session with one to three others.

TWiM 46 Letters

Jeff writes:

Hello TWIMers -  In TWIM 26  I heard the listener email asking if you would consider offering continuing education credit for your podcasts, and you understandably cited the work that would you need to do (such as writing learning objectives, tests etc) as a real barrier to that.  I was wondering if you would consider "contracting" that kind of work out to some of your listeners; being a teacher of a microbiology class at a community college, I spend a large amount of time coming up with learning objectives, tests etc  anyhow, and it would help me to generate fresh material for my students from your podcasts.  I wouldn't be surprised if there were others in your listening base who might feel the same.  This still would add work for you, so I understand if its a no-go.

In a separate vein: quite a while ago I was doing dishes and listening to a TWIM.  As I was using a sponge to wipe off the counter a ridiculous question popped into my head (as opposed to my toe, I guess): are there strains of bacteria that can provide a protective commensal role on environmental surfaces?  A counter top is nothing like a biological surface, as only the latter should have organic material to eat on it, but still, is there any evidence in any situation that something like this happens?  Please read  the following sentence with extra emphasis: I am not fishing for an excuse to get out of doing the dishes, and I regularly boil our kitchen sponges and use bleach to Pokies clean the counters.

Keep up the great work!

Velma writes:

Dear TWIM-team,

Greetings from a longtime listener and fan of all three TWI-podcasts. I'm a biotechnology Masters student at the University of Helsinki, Finland, but I earn my living as a part-time driver in the world's most northern metro. Your podcasts help me pass the dull hours at work so that I feel like I'm doing something to advance my studies as well.

I've been thinking of writing for quite a while. Now that I'm finally doing it, I have a rather general suggestion and a link. The suggestion is, I'd like to hear more about the archaea - maybe even an entire episode dedicated to them. They seem like such a mystery. At least at my home university, they're almost always just mentioned as an aside, while the bacteria get all the attention. The one time they were actually discussed on a course, I learned that they are not just extremophiles, but actually all around us, just like bacteria. This made the fact that there are no pathogenic archeae seem even more curious to me.

As for the link, it's for the Earth Microbiome Project:

I just ran across it today, and don't remember this project being mentioned on TWIM before. I think the idea is awesome, not to mention really ambitious, maybe even overly so. What do you think, is creating even a rough map of the microbiome of our entire planet an attainable goal? And would it be a useful resource for research?

Thanks for the inspiring and informative podcasts,


TWiM 45 Letters

Elitza writes:

Dear TWiM Team,

I just finished listening to the TWiM 35 on LPS in Vibrio (among other topics). Dr. Elio Schaechter mentioned a field in Microbiology that I think is of great interest to the scientific community and should definitely be covered in a podcast. The topic is: Outer Membrane Biogenesis in Gram-negative bacteria. For decades people have been hypothesizing and trying to find an evolutionary link that would answer the following questions: how did a second membrane in bacteria come about and was the last universal common ancestor (LUCA) a single or double-membraned organism. These questions are extremely difficult to address and rely heavily on bioinformatics and phylogenetic analysis.

I'm the first author of the paper that I'm suggesting here as a resource for a potential podcast. I've read extensive amounts of scientific literature before the paper was finalized and published in Cell to realize that currently, there are no favored hypotheses and the very few hypotheses that exist are highly controversial. In our paper we structurally characterize (using electron cryo-tomography) the process of endospore formation. The process is typically thought of as exclusive to Gram-positive bacteria members of the phylum Firmicutes, however, we imaged a Gram-negative organism (Acetonema longum) that is also able to sporulate! Through our structural studies, phylogenetic profiling and biochemical analysis we showed that A. longum possesses a true outer membrane. Not only that, after sporulation, the spore is surrounded by two membranes both of which originated from the inner membrane of the mother cell. Upon outgrowth, the second membrane of the spore becomes the outer membrane of the bacterium and therefore is remodeled from and inner into and outer membrane. These are fascinating new results that may provide us with a missing link between Gram-positive and Gram-negative bacteria and give insights into how an outer membrane may have evolved.

Here are a couple of links to the paper I'm suggesting and a commentary by Dr. W. Vollmer on this work:



Fabio writes:

Dear Prof. Schmidt, I listened the podcast in Microbiology that you recently contributed together with Vincent Racaniello, Joseph John and Elio Schaechter. You made a very nice summary and commentary of the International Symposium on Staphylococci held last August in Lyon.

Furthermore, I would like to thank you for all your nice words about the symposium that we organized and on our recent opinion paper titled “Inferring reasons for the failure of S. aureus vaccines in clinical trials” and published in Frontiers Cell. Inf. Microbio.

Best wishes,


Fabio Bagnoli, PhD

Project Leader

Novartis Vaccines & Diagnostics

Alice writes:

Hey TWIM-MERs -- this is from a wildlife rehab newsletter, thought you might be interested:

MRSA in Wildlife

One of the most notorious and hard-to-treat bacteria in humans has been found in wildlife, according to a new study in the Journal of Wildlife Diseases. Researchers isolated methicillin-resistant Staphylococcus aureus (MRSA) in two rabbits and a shorebird. Wild animals may act as an environmental reservoir for the disease from which humans could get infected.

Molecular typing of the isolates showed that the shorebird carried a hospital-associated strain of MRSA, while the rabbits had community-associated strains. The rabbits' MRSA also was resistant to tetracycline, which is common in farm animals.

Perhaps most troubling of all was that one of the pigeons carried a Staphylococcus bacterium that, while still sensitive to methicillin, was resistant to the antibiotic vancomycin. "Vancomycin is used as a last resort in MRSA infections," says study co-author Shylo Wardyn, “and vancomycin-resistant staph strains are rare in humans.” Abstract:

Peter writes:

Happy Halloween greetings Twim Team.

For a slightly microbiology themed Halloween costume I constructed a Plague Doctor mask.

You can see its construction on the instructables site:

Michael writes:

Hello, TWiM!

News Article:

Comment:  I feel like this issue is quite broad and interesting and was hoping that ocean geoengineering might be worth discussing.  It's my understanding that scientists are wary of such approaches, to say the least, but this event seems to demonstrate a certain necessity for the international community to come to terms with geoengineering and sort out strategies and methods.  As a layman, I'd be very interested in what you guys have to say!

Quick excerpt from the beginning of the article:

"A controversial American businessman dumped around 100 tonnes of iron sulphate into the Pacific Ocean as part of a geoengineering scheme off the west coast of Canada in July, a Guardian investigation can reveal.


Satellite images appear to confirm the claim by Californian Russ George that the iron has spawned an artificial plankton bloom as large as 10,000 square kilometres. The intention is for the plankton to absorb carbon dioxide and then sink to the ocean bed – a geoengineering technique known as ocean fertilisation that he hopes will net lucrative carbon credits.

George is the former chief executive of Planktos Inc, whose previous failed efforts to conduct large-scale commercial dumps near the Galapagos and Canary Islands led to his vessels being barred from ports by the Spanish and Ecuadorean governments. The US Environmental Protection Agency warned him that flying a US flag for his Galapagos project would violate US laws, and his activities are credited in part to the passing of international moratoria at the United Nations limiting ocean fertilisation experiments

Scientists are debating whether iron fertilisation can lock carbon into the deep ocean over the long term, and have raised concerns that it can irreparably harm ocean ecosystems, produce toxic tides and lifeless waters, and worsen ocean acidification and global warming."

Thank you for the great podcasts,



Øystein writes:

Dear TWiMmians,

I just found the latest edition of Clinical Microbiology and Infection and read about a concept that is new to me: culturomics.

Maybe you'll be as intrigued as me by this concept. It contrasts well wil all the high-throughput-genomics hype these days. It might be a good article to put on the show (some day?).

Here are the links, I am happy to forward pdf's of the articles to you if needed.

Culturomics: a new approach to study the human microbiome


Microbial culturomics: paradigm shift in the human gut microbiome study

And again, thank you for three great show to walk, commute, run, bike and do housework to:)

All the best,


Registrar in clinical microbiology

Vestfold municipal hospital, Tønsberg


TWiM 44 Letters

Jeff writes:

Hi All - I am getting to the part of my Micro class where I have students analyze antibiograms and noticed a blog pointing to the attached paper. Forgive me if this topic (antibiogram data changing as a function of when samples are taken from a patient) has already been covered or commented on, but just in case, take a look. I particulary enjoy data tables showing "time to unreliability" and boy, things sure change fast in the ICU! I would be interested to hear a program about the "ecology of antibiotic resistance" in hospitals/clinics. I can think of reasons why resistance might vary depending on location within a hospital, but not being a clinical person I have no idea what the real reasons are. Forgive me if this too has been already featured.... teaching 5 classes and then coming home two young children keeps me chronically behind.

Love the program, thank you so much!

Here is the link - I don't know if it is copyright protected or not....

Georgia Perimeter College

Katie writes:

Dear TWIM Doctors,

Thank you so much for your wonderful podcast.  I enjoy the entire TWI series, and I am thrilled that I finally have something to contribute!

In TWIM #43, a really interesting paper on bacterial caveolae was discussed. While this was amazing work, I do have to point out that being chock full of membrane vesicles is not unheard of in bacteria.  The photosynthetic purple nonsulfur bacteria (PNSB) Rhodobacter sphaeroides forms membrane vesicles in the cytoplasm to house its photosynthetic apparatus.  I have attached a paper with EM images (see Fig. 2 of the Adams and Hunter paper) showing how full these bacteria are with vesicles.  Beautiful studies by investigators such as Dr. Neil Hunter are beginning to uncover how these vesicles are formed, but there is still a lot that is not understood including what happens to these vesicles during division.  Another PNSB, Rhodopseudomonas palustris doesn’t form vesicles, but it does form lamellar membranes in the cytoplasm. If you look at the EM images in the second paper I attached, you can see that they have just a splash of cytoplasm. Considering how crowded the bacterial cytoplasm is already, it is really amazing!

Keep up the great work, and I look forward to the next podcast.


[she sent: ]

Ayush writes:

Hello TWiM team,

I enjoy listening to you all every week. I apologize that my comment here is about not-so-recent TWiM (#30) about Burkholderia pseudomallei.  Some of you may know that that Melioidosis was perhaps described (Tapanuli fever) as a bioterror agent by Sir Arthur Conan Doyle in 'The Dying Detective'.  In this story, Sherlock Holmes was sent an unknown bacterium in mail to get him killed. Here is a paper describing Holmes' encounter with the bioweapon.

Please keep up the great work. I would strongly recommend TWiM as a must-listen for every microbiologist.

Alice writes:

Soil bacteria as source of drug resistance genes - does this have implications for nosocomial infection via contamination followed by gene swapping?

Glenn writes:

TWim podcast #11

I am wondering about the comment that was mentioned about the cutting board being the most dangerous tool in the kitchen. What is the best way to clean the cutting board? Also if one was to only use quick frozen chicken and cook it without pre-thawing. Will this keep one from acquiring the transfer of microbes from chickens to human by touch. I am assuming that by cooking all meats it kills all microbes.



Glenn writes:

first I am really enjoying listening to TWiM and as a non-scientist you make the information about the micro world understandable. My question is related to TWiM podcast #16. I have several health issues that require me to take ibuprofen for pain and inflammation. How much concern should I have about the depletion of change in my gut and its ability to function properly.

thank you,


TWiM 43 Letters

Jake writes:

Hello Vincent,
I've been listening to your TWiM podcast now for a few weeks as I am a student at SDSU taking a microbial genetics class with stanley maloy.  It be be another few months until I've caught up to the current episodes.  I saw this recent article on phage use in cleaning up achne and thought you'd like to hear about it.


Franco writes:

The article by Frits R. Mooi et al. linked on the episode “The sound of whooping cough” is contradicted by a study published on the current issue of EID: Schmidtke AJ, Boney KO, Martin SW, Skoff TH, Tondella ML, Tatti KM. Population diversity among Bordetella pertussis isolates, United States, 1935–2009. Emerg Infect Dis  Volume 18, Number 8—August 2012

I would greatly appreciate a comment on this point.

Best regards
Dr. Franco Giovanetti

John writes:

Dear TWIMmers,

I just finished listening to TWIM #39 (yes, I'm behind) and I had a question about the paper Michael reviewed.  Let me spell out how I understood the discussion, and then maybe you can tell me if I've misunderstood something, or if my question even makes sense.

Michael was talking about the question of how mutations arise and are selected for in nature.  The idea supported by Darwin (though long before anyone knew about DNA) was that mutations were in some sense driven by stress, right?  And then, there was this famous experiment which showed that mutants were present in the population before selection pressure was applied--a bunch of microbes were put on a plate with some antibiotic, and a small fraction of them were mutants that had resistance genes.  In this case, there was no pressure on the microbes to adapt the the antibiotic until they were put in a situation where they died unless they had the resistance genes.  Is this right so far?

Then, there was a second experiment, which used less powerful selection--the microbes were put on a plate where the only source of carbon was lactose, which the normal population of these microbes couldn't use for carbon.  And at first, these didn't grow much, but over time, even in an environment where the normal microbes couldn't grow Buy Viagra at all and so selection shouldn't have been able to bring anything new about, some microbes arose that could grow under these conditions.  Again, have I understood the basic idea?

Now, this is where I got a little confused.  From Michael's explanation, what I got was the idea that a bacterial cell can mutate in place even when it's not dividing.  That is, even in these bacteria that were sitting there unable to divide because they couldn't get any carbon from their environment, mutations could arise over time, and this led to a population of microbes that started out without the ability to grow with no carbon sources other than lactose, and then a few mutations arose that allowed some growth.  Is this right?  Is this kind of mutation important in eukaryotic cells, say in cancer or cellular senescence?

An alternative seems to be that the bacteria started out with a huge diversity of mutations already present, many of which gave them some small ability to get carbon from the lactose.  Then, over time, it seems like those would do all the dividing, and you'd get something like classic selection, with the bacteria that could reproduce faster leaving more copies of themselves which themselves could mutate to get better at reproducing.  Was there something observable in the experiment that ruled this out?

Anyway, thanks for answering my amateur questions.  I'm a computer scientist with no biology background, so I apologize if I'm making some dumb mistakes somewhere.

I wanted to also point out a really fun quote I ran across awhile back.  It's in a very old book (_Mutual Aid: A Factor in Evolution_ by Petr Kropotkin)--I think it was published in 1902.  It was a kind of argument against social Darwinism from a Russian naturalist and anarchist, combining observations on history and nature both.

> Mutual aid is met with even amidst the lowest animals, and we must be prepared to learn some day, from the students of microscopical pond-life, facts of unconscious mutual support, even from the life of micro-organisms.

Reading this, the words "biofilms" and "quorum sensing" popped immediately into my head.  Along with all the other kinds of mutualism between microbes.

Thanks again for your wonderful podcasts,


TWiM 42 Letters

Sarah writes:

Hi Twimologists!

I just found this wonderfully instructive paper on concepts of bacterial ecology that are relevant to the antimicrobial resistance problem (doi: 10.1086/340245,link). The author mentioned the existence of genes conferring resistance to metallic ions like copper, which reminded me of the discussion about copper surfaces from TWiM episode 1. I hate to ask because it involves chemistry which we ALL took ages ago, but could you comment on this? (Dr. Maloy?)

A lot of papers about copper resistance in bacteria came out before Y2K, such as the above paper's reference # 47. But this paper just talks about metabolism of ionic copper, which is different than metallic or solid state copper (if I remember right). However, a 2004 paper (link) in BMC Microbiology suggests that metallic copper releases copper ions which are transferred into bacterial cells when a bacterial suspension is incubated in a copper vessel.

So, is it futile to celebrate the antimicrobial properties of copper surfaces, or is metallic copper reliably antibacterial by brute force, able to overcome any resistance gene that lets bacteria metabolize copper ions?

Sarah, BS, BSN, RN, Infection Preventionist

Peter writes:

I am not sure if the BBC programme Horizon is available in America but I found  the recent edition on combating antibiotic resistant bacteria was very interesting.
Of particular note were the interviews with Dr David Harper of AmpliPhi BioSciences in England on the development of bacteriophages to fight bacterial infections and Professor Viagra 100mg Bonnie  Bassler of Princeton University who is investigating  using antagonists to bacterial quorum sensing compounds to moderate their pathological effects.

I think that these scientists would make good guests for TWiM.

Behzad writes:

It is always a delight hear Vincent chairing these informal and incredibly informative podcast discussions of microbiology.  The world should be eternally grateful for what he is achieving and making so accessible both through smart phone streaming and on the web.  He engages his panelists enthusiastically as they discuss a wide range of topics important to understanding the diversity of microbes and their to understanding infection, ecology and even climate!

Hearing Elio is particularly rewarding as he is, dare I say, even more articulate than Vincent as he explains his topics clearly in terms that non-experts can understand and, importantly, puts these into historical context.

I do hope that this message is communicated to the shows sponsor, ASM.

Keep up the great work!

Steve writes:

Of course, I immensely enjoy the podcasts. Thanks for making front-line science so accessible and informative. This is something America, society needs -- a more intimate, clear-eyed look at science and scientists in action.

Are there transcripts available for the TWIM podcasts? If not, is this something planned or in process? If not, I would help transcribe and index the text to the audio/video files.



Abhinav writes:

Why do only a few bacteria out of billions act as endophytes by entering tissues of plants?

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