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TWiM 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.
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:
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.
Fabio Bagnoli, PhD
Novartis Vaccines & Diagnostics
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: http://www.jwildlifedis.org/content/48/4/1069.abstractlink
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:
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,
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, TønsbergNorway
Dear TWiM Team
I see that some action is now being taken in America against the non-therapeutic use of antibiotics as livestock growth promoters:
Having read the FDA Press Announcement I think that that the N.Y. Times article may be misleadingly optimistic, I feel that this is probably too little and too late.
The practise of using antibiotics as growth promoters was stopped in Sweden in 1986 the UK in 1988 and in Europe by 2005, without significant adverse effects on the meat industry.
As I see it the only reason this practise persists in America is the lobbying by the livestock industry against the scientific consensus.
Your views please doctors.
Article about how use of AGP's was phased out in the Danish pork industry:
Antibiotic Growth Promoters in Agriculture: History and Mode of Action:
History of the Use of Antibiotic as Growth Promoters in European Poultry Feeds:
I have a question for Michael Schmidt. While doing my research on R. solanacearum, I read an old paper where they mentioned that Pseudomonads were able to internalize copper and therefore detoxify a copper rich liquid medium, I have observed this myself with the R. solanacearum strain I was working with, but since Michael is the copper expert in TWIM, I would like to know if there is some more new information about this phenomenon. It is of my interest beyond my doctoral thesis because copper is one of the few fungicides allowed to be used in organic farming. Therefore, this phenomenon deserves more attention from organic farmers, I think.
Ph.D. in Biocontrol Science Electronic Cigarette
Tokyo University of Agriculture and Technology
United Graduate School of Agricultural Science
Biocontrol Science Department
Instituto de Investigaciones Fármaco-Bioquímicas
La Paz, Bolivia
You know how sometimes you run across a word or phrase which sounds like it's got a specific meaning that's really important to the context of whatever you're reading or hearing?
Well, I've been catching up with episodes 27-29 lately, and true to TWi form, the phrase "type III secretion" got the gears crankin'. The phrase sounded significant but I didn't remember learning about secretion mechanisms under this framework in undergrad 10 years ago. I did a little reading and wanted to share how fascinating these mechanisms are and how relevant they seem to be for many common human pathogens. Depending on the bug, the product, and the environment, these guys can deliver a variety of toxins into the extracellular environment, spit out antibiotics and other compounds, or deliver proteins or nucleic acid directly into target cells via injection or vesicles. What a spectacular array of intricate and elegant mechanisms - as Dr. Schmidt would say, "Remarkable!"
It's fitting that these podcasts are award-winning. They always nurture curiosity and prompt trains of thought into unexplored territory.
The discussion about TUNEL and apoptosis in episode 29 reminded me of a suggestion for pick of the week - A couple of music videos that Roche released in 2009 to promote some new lab tools to measure viability and cytotoxicity. They're more for tissue culture than microbiology, but hilarious nonetheless.
(in case the above links don't work: http://www.roche-applied-science.com/usa/celldeathtour/)
Horizontal transfer between blogs.
Dear TWiM Team
A fascinating article from New Scientist this week.
Standard medical teaching is that the foetus is sterile and that the microbiome only begins to develop post natal.
New research from Spain indicates that the microbiome starts to develop before birth:
"Pilar Francino and her colleagues at the University of Valencia in Spain collected and froze the meconium of babies from 20 women. They removed the outer layers of each sample to rule out any bacteria picked up after birth, then looked for bacterial DNA.
The team not only identified bacteria in the babies' meconium - which before then was thought to be sterile - they found bacterial communities so developed that they seemed to fall into two categories. Around half of the samples appeared to be dominated by bacteria that produce lactic acid, such as lactobacillus, while the other half mostly contained a family of so-called enteric bacteria, such as Escherichia coli."
Dear TWiM Team
There was an interesting article in the March Scientific American on long term effect on health that food poisoning can cause:
New studies by scientists in several countries show that food poisoning rather than lasting just a few unpleasant days can in some cases cause life long problems.
Though this possibility has been known for some time the recent work indicates that this phenomenon is much more common than previously thought.
"A survey of 101,855 residents of Sweden who were made sick by food between 1997 and 2004 found Electronic Cigarette, for instance, that they had higher-than-normal rates of aortic aneurysms, ulcerative colitis and reactive arthritis."
"...several years after a 2005 outbreak of Salmonella in Spain, 65 percent of 248 victims said they had developed joint or muscle pain or stiffness, compared with 24 percent of a control group who were not affected by the outbreak."
PS I that the Scientific American journalist and author Maryn McKenna would be a good guest for TWiM or TWiV.
Hey thanks for the great podcast. TWiM is one of my new favourites. (I'm about to post a review on my blog.) I'm a little afraid to start listening to TWiP and TWiV--if I get hooked I'll never be able to keep up with all of them.
I just listened to your episode that included the paper on the autism microbiome study, and one of you said something about it being difficult to recruit controls for this kind of invasive procedure. It might make the statistics more complicated, but what about recruiting siblings of autistic kids as controls? The parents would be much more likely to be on board, as they have a vested interest in the progression of science on the problem of autism.
Hello Vincent and cast of TWIM;
I have to say, even though I am a novice, I really enjoy your podcasts.
Because of the nerdy-ness and nature of this song, I thought I should pass it along. Happy St Patrick's Day! Enjoy!