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TWiM 18 Letters

Tim writes:

this recent publication struck me as being interesting and relevant, however I'm not sure I have the background to completely understand it -- as wondering if you would comment on this publication.


Here's part of the press release from the University of California at Davis:


Lyme disease bacteria take cover in lymph nodes

The bacteria that cause Lyme disease, one of the most important emerging diseases in the United States, appear to hide out in the lymph nodes, triggering a significant immune response, but one that is not strong enough to rout the infection, report researchers at the University of California, Davis.

Results from this groundbreaking study involving mice may explain why some people experience repeated infections of Lyme disease. The study appears online in the journal Public Library of Science Biology at: http://tinyurl.com/3vs8pm9.

"Our findings suggest for the first time that Borrelia burgdorferi, the bacteria that cause Lyme disease in people, dogs and wildlife, have developed a novel strategy for subverting the immune response of the animals they infect," said Professor Nicole Baumgarth, an authority on immune responses at the UC Davis Center for Comparative Medicine.

"At first it seems counter intuitive that an infectious organism would choose to migrate to the lymph nodes where it would automatically trigger an immune response in the host animal," Baumgarth said. "But B. burgdorferi have apparently struck an intricate balance that allows the bacteria to both provoke and elude the animal's immune response."


here is where I found the press release..


here's a copy of the original article (at PLOS)...



thanks again... i'd love to hear your analysis of what is going on here...

Tom writes:

Hello to the Microbiology crew!

While recently reading the *gasp* wikipedia page on "Phytic acid", I found a paragraph of content near the end that threw me for a loop. The claims were cited to an article from the Journal of Biochemistry (http://www.jbc.org/content/early/2010/04/29/jbc.M110.126581.long) stating "Ironically, [phytic acid] is shown to be a required cofactor for YopJ, a toxin from Yersinia pestis.[27] It is also a required cofactor for the related toxin AvrA from Salmonella typhimurium[27]". Perhaps it is only the choice of the word "ironically" that confuses me, but the dynamic seems fascinating.

I'm trying to posit a few plausible sounding explanations, but my biochem is limited, so i'm working from a pop understanding of microbial ecology and evolution.

I kind of get that phosphate (as a key nutrient) is tightly sequestered in phytic acid, much like chelation complexes for metals, but I can't see why it would be advantageous for Y. pestis to have maintained the cofactor dependency to the *toxin* this long. I know E. coli pulls a similar trick by chelating the heck out of free iron (enterobactin, i think), but the fact that the compounds are function labeled "toxin, versus 'iron-aquirer'' skews my intuition.

I guess I'm struggling to understand the genetic logic behind the cofactor. My assumption is that the phytic acid is somehow integrated into Y. pestis' metabolism (maybe the phosphate groups Viagra 100mg are hydrolyzed and absorbed by the Y. pestis?), but from what little i could decipher from the paper, no mechanism for re absorption seems present (only injection).

I suppose it could always be neutral evolution (increasing complexity w/ negligible benefit, see http://skepticwonder.fieldofscience.com/2010/03/in-defense-of-constructive-neutral.html), but the pathways involved seem too tightly regulated to be purely non-advantage yielding for either organism.

If you have the time, I'd love to really take a more rigorous stab at understanding this dynamic (and the paper, of course), both from a biochemical and ecological level.

Thank you very much for your time,

David writes:

Episode #11 was an especially interesting one.  I’d like to add to the discussion from Joe’s letter about entropy, from a straight physics perspective.  The 2nd law of thermodynamics (incorrectly referred to as the 3rd law in the letter) has several different but equivalent versions.  The version probably most relevant to this discussion is roughly stated as “In a isolated system, the entropy (disorder) tends to increase in time.”  Note the first part of this version (“In a isolated system”), is often left out when most people state the 2nd law.  The first-part-left-out statement has led some creationists to incorrectly state that the 2nd law prevents evolution from occurring.  People make the mistake of trying to apply the 2nd law to non-isolated systems, which leads to wrong conclusions.

The Earth is an open (non-isolated) system due to the sun.  Because the Earth is open, taking in energy from the sun, matter has energy available to organize itself.  From snowflakes to hurricanes, from viruses to humans, clumps of matter are constantly using energy to decrease or maintain their entropy.  There are many interesting ways that life uses various forms of energy to this, but ultimately it is the availability of energy that gives life the ability to organize.  So life doesn’t “cheat” or “get around” the 2nd law, it obeys the 2nd law (when it finds itself as an isolated system).

-- David

Michael writes:

Greetings TWiM crew!

As someone who spends most of his time on the macroscopic world (animal biomechanics), I have found TWiM to be a wonderful way to get a little foray into the rest (=most) of the biological world each week.  Thank you for making it all happen.

Onto the question: is there any particularly good resource (say, for example, a text or large review manuscript) that has synthesized the current perspectives on biomechanical approaches to microbiology?  I'm familiar with some bits of work in that realm, such as the bacterial fluid mechanics work being done by Kenny Breuer and Tom Powers (mostly because I know Kenny), but I have found it difficult to find any location where this sort of perspective is examined and reviewed at a more general scale.  There have been some nice mentions of microbial biomech in TWiM (such as the discussions of low Reynolds Number flows, where viscous effects dominate), and so I thought perhaps you all knew a good go-to source.


Michael Habib
Assistant Professor of Biology
Chatham University

Comments (1)

  1. Tim So much is known about Borrelia but ignored lectures by Microbiologist Tom Grier can be found on my blog but too long to post here. He explains reasons why Microbiologists are not finding Borrelia by modern techniques and also talks about work done by Miklossy and Paschner finding Lyme on the brain (part 4 of his lectures) In Paschner's mouse model 20 years ago the strain injected in the tail of the mouse had morphed within 4 weeks and was different from what was harvested from the brain of the mouse.

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