In article <49cj03$5jm at news.nstn.ca>, Dave Edgell <dedgell at ac.dal.ca> wrote:
>dasnyder at uci.edu (David Snyder) wrote:
>>Any information on phylogenic trees for Thermotoga maratima out there? I
>>notice a paucity of information about this very interesting bacterium that
>>would be good for evolutionary studies... this is why the cross-posting,
>>hope no-one minds.
>>The 16S rRNA has been sequenced from Thermotoga which places this
>organism near the base of the eubacteria. A few other genes have
>been sequenced but none as phylogenetically useful as rRNA. Check
>out any publication by Woese or cronies for a tree which shows
>where Thermotoga branches.
>
There are several genes that appear to be more phylogenetically useful than
16S RNA. One of these is the glutamine synthetase gene and dendrograms
constructed using these sequences tend to show that Thermotoga maritima
clusters with the gram postive bacteria and the archaebacteria - well
within the prokaryotic group. Brown et al. (1994) state,
"The close proximity of the GSI genes of Thermotoga to those of
archae and Gram-positive bacteria is an additional and very
striking conflict with 16S rRNA (ref.) and EF-G (ref) -based
phylogenies, which tend to place this species as one of the
deepest branches of the bacterial tree."
Brown et al. (1994) then go on to compile a list of all Thermotoga genes
that have been sequenced and they conclude that the majority support
a close relationship between Thermotoga and Gram-positive bacteria.
Some other Thermotoga genes have subsequently been sequenced (ie. ribosomal
protein genes; Sanangelatoni et al. (1994)). In most cases the dendrograms
constructed from these sequences also suggest that Thermotoga is not the
deepest branch of the bacteria tree but is related to the Gram-positive
bacteria.
It's true that Woese and his "cronies" claim that the 16S RNA sequences
are the best phylogenetic markers. It's also true that many others
dispute this claim.
Laurence A. Moran (Larry)
Brown, J.R., Masuchi, Y., Robb, F.T. and Doolittle, W.F. (1994) Evolutionary
Relationship of Bacterial and Archaeal Glutamine Synthetase Genes.
J. Mol. Evol. 38, 566-576.
Sanangelantoni, A.M., Bocchetta, M., Cammarano, P. and Tiboni, O. (1994)
Phylogenetic Depth of S10 and spc Operons: Cloning and Sequencing
of a Ribosomal Protein Gene Cluster from the Extremely Thermophilic
Bacterium Thermotoga maritima. J. Bacteriol. 176, 7703-7710.
