Re: here are some interesting free texts from Blaser

[Guest guest]

Well, the first one was not too stimulating for me. The second one had

lots of really fascinating ideas. (And also a lot that I disagreed

with, but it doesnt really matter).

> Aim to read these raptly, soon as ah finish m' onerous chores. Both

free:

>

> http://www.nature.com/embor/journal/v7/n10/pdf/7400812.pdf

> http://malthus.micro.med.umich.edu/lab/pubs/nature06198.pdf

>

[Guest guest]

> Well, the first one was not too stimulating for me. The second one had

> lots of really fascinating ideas. (And also a lot that I disagreed

> with, but it doesnt really matter).

Some of the most interesting novel refs from the one I liked:

Salmonella typhi, the causative agent of typhoid fever, is

approximately 50,000 years old.

Kidgell C, Reichard U, Wain J, Linz B, Torpdahl M, Dougan G, Achtman M.

Centre for Molecular Microbiology and Infection, Imperial College of

Science, Technology and Medicine, The Flowers Building, Exhibition

Road, South Kensington, London SW7 2AY, UK.

A global collection of 26 isolates of Salmonella typhi was

investigated by sequencing a total of 3336 bp in seven housekeeping

genes. Only three polymorphic sites were found and the isolates fell

into four sequence types. These results show that S. typhi is a recent

clone whose last common ancestor existed so recently that multiple

mutations have not yet accumulated. Based on molecular clock rates for

the accumulation of synonymous polymorphisms, we estimate that the

last common ancestor of S. typhi existed 15,000-150,000 years ago,

during the human hunter-gatherer phase and prior to the development of

agriculture and the domestication of animals.

PMID: 12797999 [PubMed - indexed for MEDLINE]

Proc Natl Acad Sci U S A. 2004 Apr 6;101(14):4871-6. Epub 2004 Mar

23.Click here to read Click here to read Links

Comment in:

Proc Natl Acad Sci U S A. 2004 Apr 6;101(14):4721-2.

Stable association between strains of Mycobacterium tuberculosis

and their human host populations.

Hirsh AE, Tsolaki AG, DeRiemer K, Feldman MW, Small PM.

Department of Biological Sciences, Stanford University, Stanford,

CA 94305, USA. aehirsh@...

Mycobacterium tuberculosis is an important human pathogen in

virtually every part of the world. Here we investigate whether

distinct strains of M. tuberculosis infect different human populations

and whether associations between host and pathogen populations are

stable despite global traffic and the convergence of diverse strains

of the pathogen in cosmopolitan urban centers. The recent global

movement and transmission history of 100 M. tuberculosis isolates was

inferred from a molecular epidemiologic study of tuberculosis that

spans 12 years. Genetic relationships among these isolates were

deduced from the distribution of large genomic deletions, which were

identified by DNA microarray and confirmed by PCR and sequence

analysis. Phylogenetic analysis of these deletions indicates that they

are unique event polymorphisms and that horizontal gene transfer is

extremely rare in M. tuberculosis. In conjunction with the

epidemiological data, phylogenies reveal three large phylogeographic

regions. A host's region of origin is predictive of the strain of

tuberculosis he or she carries, and this association remains strong

even when transmission takes place in a cosmopolitan urban center

outside of the region of origin. Approximate dating of the time since

divergence of East Asian and Philippine clades of M. tuberculosis

suggests that these lineages diverged centuries ago. Thus,

associations between host and pathogen populations appear to be highly

stable.

PMID: 15041743 [PubMed - indexed for MEDLINE]

Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2869-73. Epub 2006 Feb

13.Click here to read Click here to read Links

Variable host-pathogen compatibility in Mycobacterium tuberculosis.

Gagneux S, DeRiemer K, Van T, Kato-Maeda M, de Jong BC, Narayanan

S, Nicol M, Niemann S, Kremer K, Gutierrez MC, Hilty M, Hopewell PC,

Small PM.

Institute for Systems Biology, Seattle, WA 98103, USA.

sgagneux@...

Mycobacterium tuberculosis remains a major cause of morbidity and

mortality worldwide. Studies have reported human pathogens to have

geographically structured population genetics, some of which have been

linked to ancient human migrations. However, no study has addressed

the potential evolutionary consequences of such longstanding

human-pathogen associations. Here, we demonstrate that the global

population structure of M. tuberculosis is defined by six

phylogeographical lineages, each associated with specific, sympatric

human populations. In an urban cosmopolitan environment, mycobacterial

lineages were much more likely to spread in sympatric than in

allopatric patient populations. Tuberculosis cases that did occur in

allopatric hosts disproportionately involved high-risk individuals

with impaired host resistance. These observations suggest that

mycobacterial lineages are adapted to particular human populations. If

confirmed, our findings have important implications for tuberculosis

control and vaccine development.

PMID: 16477032 [PubMed - indexed for MEDLINE]