Re: Surprising diversity in bacteria genomes

From: David C Campbell <amblema@bama.ua.edu>
Date: Fri Sep 23 2005 - 13:24:04 EDT

>Another problem for evolution that the new genome data are presenting
is the high diversity of cousin species. Evolution predicts a high
degree of homology between genomes of cousin species. Evolutionists
were surprised to find that, instead, similar species consistently have
their own, unique genes. Initially evolutionists thought that
homologies for these unique genes would soon be found after a few more
similar species were sequenced. But instead, they just continued to
yield new, unique genes. Now they are finally dropping the prediction
altogether. A new paper out of TIGR discusses the genome of a
Streptococcus species, and concludes there will be no closure on
homologies. It is summarized in the piece below.<

As the subject line indicates, the article is only talking about
bacteria. Bacteria are so small that there's not much to go on
morphologically. Thus, a bacterial "species" is probably much more
like a "family" of animals.

Also, bacteria and viruses reproduce and evolve very rapidly, so trying
to characterize a genome is a moving target.

Nevertheless, there is high homology between closely related bacterial
strains. The article found over 80% consistency between strains. What
was quoted did not categorize the remaining 20%. Do any two strains
differ by that much? More likely, some extra genes occur in some and
some genes are missing in some, so that any two have rather more than
80% similarity. An extra plasmid, taken up from a different bacterium,
in one strain could easily make a large difference in such a count.

Similar species of animals have very high similarity. However, at
least a few genetic differences are expected evolutionarily-after all,
they are different species/strains/whatevers. Very few complete
eukaryotic genomes are available, relative to the number of bacterial
genomes, though current projects will start to give a more complete and
evolutionarily meaningfull picture.

----------------------------------------
Dr. David Campbell
425 Scientific Collections
University of Alabama, Box 870345
Tuscaloosa AL 35487
"James gave the huffle of a snail in
danger But no one heard him at all" A.
A. Milne
Received on Fri Sep 23 13:25:48 2005

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