kailash at jnuniv.ernet.in wrote:
>> Dear Netters,
> I have a query.
> In a common environment, despite horizontal gene transfer,
> how is it made possible by the microorganisms, sharing the
> same environment, to maintain their individual identity?
> i.e. why two microorganisms do not change so significantly
> in their genome due to horizontal gene transfer that they
> merge and a third absolutely new organism if formed.
> Bye for now
> i p singh.
Although I am not claiming horizontal gene transfer does not occur, I
believe it is and has always been a very rare event. The main seminal
papers on the subject are by R.F.Doolittle et al, where he suggests a
number of likely and a few possible occurences of this in evolution.
Last year I repeated one of his firmest test cases
(glyceraldehyde-3-phosphate dehydrogenase in E.coli) and found his
conclusions to be no longer valid. A phylogeny covering the current
content of the protein databases (much expanded since the original work)
showed clearly that the E.coli gene in question was in it's perfect
taxonomic position and that no horizontal gene transfer had taken place.
This work has not been published. However, a repeat of the Fe/Mn
Superoxide Dismutase phylogeny has held up and h-t-g probably did occur
with this gene in entamoeba hystolytica.
SmithKline Beecham Pharmaceuticals
Simon_Topp-1 at sbphrd.com