Blasto. hominis - question for Judy D.
mcorriss at gate.net
Mon Jul 8 10:15:05 EST 2002
This is one of the great benefits of the internet: direct communication
with the actual primary researchers.
Glad to hear from you, Dr. Clark.
I had pretty much given up thumbing through paper piles (I was turning
up mostly dinosaur papers, anyhow) and planned to hit the hospital's
medical library this Monday afternoon. I was unable to sooner because of
the long July 4th holiday weekend and the library was locked-up. After
26 years, I'm still unable to get the administration to give me a
magnetic pass into the library that all the interns and physicians have.
The paper was published a little longer ago than I had remembered ;-)
_Proteromonas_, yes! When the interns would appear in my lab to view our
occasional positive specimens, and I had just read the paper (1996), I'd
mention the lizard flagellate, as well as the cellulose digesting
termite commensals as being stramenopiles, but the only recognition was
to the red algae (_Fucus_ - not even recognised by that name, though)
and diatoms. I guess over the years, I've degenerated to just mentioning
I used to have a dried and stained slide of what I thought was
_Proteromonas_ that came from my sister's 5 foot iguana. I'll have to
check her current iguana.
I have done a variety of stains to dried smears and have noted that the
staining of _Blastocystis_ was similar to that of _Trichomonas_ and am
not surprised that it may have secondarily lost flagellae. Living in low
oxygen tension in the gut, bathed with nutrition waiting to be adsorbed,
it need not expend energy supporting organelles that are not needed and
so is stripped down to bare essentials. But being different than other
gut parasites, it seems possible that it may have unique metabolic
pathways that may be exploited for treating those who may be infected
with it. Also it's not surprising that the common remedies for other gut
ailments are less successful.
Michael Patrick Corriss
mcorriss at gate.net
Graham Clark wrote:
> Dear Group, especially Judy and Michael,
> As one of the authors, I thought I should give you the citation of the
> Nature paper to stop Michael from having to wade through his piles of
> Silberman, J.D., Sogin, M.L., Leipe, D.D., Clark, C.G. 1996 Human
> parasite finds taxonomic home. Nature 380: 398
> Blasto's closest relative is actually Proteromonas, an intestinal
> flagellate of reptiles and amphibia (commensal). Presumably Blasto its
> has lost its flagella secondarily, leading to the rather boring looking
> organism we see today.
> I have studied Blasto almost exclusively in culture, so perhaps I am
> out of my depth here, but, like Stenzel and Boreham, I suspect that a
> lot of the morpgological forms described in the literature are actually
> artefacts - cells in the process of degeneration following exposure to
> oxygen. Certainly that is the implication of a short paper by Vdovenko
> (Parasitol Res 2000 Jan;86(1):8-10 Blastocystis hominis: origin and
> significance of vacuolar and granular forms).
> As far as its role in disease is concerned, I believe we will never
> find out until people start taking into account the extraordinary
> genetic diversity of the organism. Looking at ribosomal RNA gene
> sequences, we found that isolates from humans can differ by up to 7%
> which is a huge amount for this gene (Clark, C.G. 1997 Extensive genetic
> diversity in Blastocystis hominis. Mol. Biochem. Parasitol. 87: 79-83).
> I described 7 genetic types in that paper and I and others have
> subsequently found a number of additional types. Blastocystis hominis is
> clearly a species complex. But given that almost all Blasto
> identification is based on microscopy alone, if only one or a few of the
> genetic types are capable of causing disease it is not surprising that
> population surveys find no link between Blasto and symptoms. If anyone
> has any ideas on how to persuade funders that this is a worthwhile
> project I'd love to hear from you!
> Glad to know someone else out there finds this organism to be
> Best wishes,
> C. Graham Clark, Ph.D.
> Infectious and Tropical Diseases,
> London School of Hygiene & Tropical Medicine, Keppel Street, London
> WC1E 7HT, England, G.B.
> Tel: 44-207-927-2351
> FAX: 44-207-636-8739
> Entamoeba Homepage- www.lshtm.ac.uk/itd/units/pmbbu/enta/
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