Have archaeal genes contributed to bacterial virulence?

Uri Gophna, Robert L. Charlebois and W. Ford Doolittle

Trends in Microbiology 2004, 12:213-219

Although archaea have not been described as pathogens, it has recently been
suggested that genes transferred from archaea might specifically contribute
to bacterial virulence. Here, we survey 73 genomes of bacterial pathogens
for the presence of genes originating from archaea. We describe 43 cases in
which acquisition of archaeal genes by bacterial pathogens can be
demonstrated. Although no bona fide virulence factors are among these
acquired genes, several of them probably affect pathogen-host interactions.

Archaea are as diverse as bacteria and as widely distributed around the
world. It is therefore mysterious that there are no diseases of archaeal
origin. Eckburg and colleagues [1] have recently reasoned that such
disorders might have been systematically overlooked, whereas Faguy [2] has
suggested a different context in which archaea could be relevant to disease:
as donors through lateral gene transfer (LGT) of virulence-promoting genes
to pathogenic bacteria. When the genome of Escherichia coli O157:H7 was
compared with that of K12, half a dozen O157:H7-specific genes could be
recognized as having been derived from archaea [2]. In one case, an indirect
argument for a role in infectivity or virulence could be made. Faguy argued
on a more general basis that, for truly novel innovations in pathogenesis,
bacteria might have often dipped into the archaeal gene pool. The idea has
an unconventional appeal and would support claims for the medical relevance
in studying archaea. There are nevertheless two reasons to be skeptical of
such a notion. First, the divergence between bacteria and archaea is
believed to be ancient and reflected in significant structural and
biochemical differences between them, differences that should make
successful LGT difficult. In particular, archaeal proteins involved in
transcription and the DNA signals they recognize resemble their eukaryotic
homologs much more than their bacterial counterparts (for reviews see Refs
[3,4] ). Nevertheless, recent sequencing of archaeal and bacterial genomes
has shown that inter-domain transfer is not uncommon [5,6] and in some
extreme cases even rampant. Consequently, a large fraction of Thermotoga
maritima genes appears to have archaeal origins [7,8] , and the archaeon
Methanosarcina mazei bears a multitude of bacterial-derived genes,
comprising up to a third of its genome [9].

Read the rest at BioMedNet
http://gateways.bmn.com/magazine/article?pii=S0966842X0400068X

Comment:
These findings might point to the evolutionary order of single celled
animals.

Posted by
Robert Karl Stonjek.
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