Re: Re: here are some interesting free texts from Blaser

[Guest guest]

Very interesting that microorganisms may have been a causative factor in human migration. It never occurred to me but makes sense. I've always wondered why people would choose to live in freezing climates like Alaska. What if it was to get away from illness? Not that the people at the time would know what was causing disease, just that when people moved to a different climate (like a colder one) they didn't get sick (and assumed they were pleasing the gods somehow?). Something to ponder. penny <usenethod@...> wrote: > 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, isapproximately 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 ofScience, Technology and Medicine, The Flowers Building, ExhibitionRoad, South Kensington, London SW7 2AY, UK.A global collection of 26 isolates of Salmonella typhi wasinvestigated by sequencing a total of 3336 bp in seven housekeepinggenes. Only three polymorphic sites were found and the isolates fellinto four

sequence types. These results show that S. typhi is a recentclone whose last common ancestor existed so recently that multiplemutations have not yet accumulated. Based on molecular clock rates forthe accumulation of synonymous polymorphisms, we estimate that thelast common ancestor of S. typhi existed 15,000-150,000 years ago,during the human hunter-gatherer phase and prior to the development ofagriculture 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 Mar23.Click here to read Click here to read LinksComment in:Proc Natl Acad Sci U S A. 2004 Apr 6;101(14):4721-2. Stable association between strains of Mycobacterium tuberculosisand their human host populations.Hirsh AE, Tsolaki AG, DeRiemer K, Feldman MW, Small PM.Department of Biological Sciences, Stanford University, Stanford,CA 94305,

USA. aehirshstanford (DOT) eduMycobacterium tuberculosis is an important human pathogen invirtually every part of the world. Here we investigate whetherdistinct strains of M. tuberculosis infect different human populationsand whether associations between host and pathogen populations arestable despite global traffic and the convergence of diverse strainsof the pathogen in cosmopolitan urban centers. The recent globalmovement and transmission history of 100 M. tuberculosis isolates wasinferred from a molecular epidemiologic study of tuberculosis thatspans 12 years. Genetic relationships among these isolates werededuced from the distribution of large genomic deletions, which wereidentified by DNA microarray and confirmed by PCR and sequenceanalysis. Phylogenetic analysis of these deletions indicates that theyare unique event polymorphisms and that horizontal gene transfer

isextremely rare in M. tuberculosis. In conjunction with theepidemiological data, phylogenies reveal three large phylogeographicregions. A host's region of origin is predictive of the strain oftuberculosis he or she carries, and this association remains strongeven when transmission takes place in a cosmopolitan urban centeroutside of the region of origin. Approximate dating of the time sincedivergence of East Asian and Philippine clades of M. tuberculosissuggests that these lineages diverged centuries ago. Thus,associations between host and pathogen populations appear to be highlystable.PMID: 15041743 [PubMed - indexed for MEDLINE]Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2869-73. Epub 2006 Feb13.Click here to read Click here to read LinksVariable host-pathogen compatibility in Mycobacterium tuberculosis.Gagneux S, DeRiemer K, Van T, Kato-Maeda M, de Jong BC, NarayananS, Nicol M, Niemann S,

Kremer K, Gutierrez MC, Hilty M, Hopewell PC,Small PM.Institute for Systems Biology, Seattle, WA 98103, USA.sgagneuxsystemsbiology (DOT) orgMycobacterium tuberculosis remains a major cause of morbidity andmortality worldwide. Studies have reported human pathogens to havegeographically structured population genetics, some of which have beenlinked to ancient human migrations. However, no study has addressedthe potential evolutionary consequences of such longstandinghuman-pathogen associations. Here, we demonstrate that the globalpopulation structure of M. tuberculosis is defined by sixphylogeographical lineages, each associated with specific, sympatrichuman populations. In an urban cosmopolitan environment, mycobacteriallineages were much more likely to spread in sympatric than inallopatric patient populations. Tuberculosis cases that did occur inallopatric

hosts disproportionately involved high-risk individualswith impaired host resistance. These observations suggest thatmycobacterial lineages are adapted to particular human populations. Ifconfirmed, our findings have important implications for tuberculosiscontrol and vaccine development.PMID: 16477032 [PubMed - indexed for MEDLINE]