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J. Bacteriol., 03 1997, 1734-1747, Vol 179, No. 5
TM Gruber and DA Bryant
Sigma factors of the sigma70 family were used as a phylogenetic tool to
compare evolutionary relationships among eubacteria. Several new sigma
factor genes were cloned and sequenced to increase the variety of available
sequences. Forty-two group 1 sigma factor sequences of various species were
analyzed with the help of a distance matrix method to establish a
phylogenetic tree. The tree derived by using sigma factors yielded
subdivisions, including low-G+C and high-G+C gram- positive bacteria,
cyanobacteria, and the alpha, beta, gamma, and delta subdivisions of
proteobacteria, consistent with major bacterial groups found in trees
derived from analyses with other molecules. However, some groupings (e.g.,
the chlamydiae, mycoplasmas, and green sulfur bacteria) are found in
different positions than for trees obtained by using other molecular
markers. A direct comparison to the most extensively used molecule in
systematic studies, small-subunit rRNA, was made by deriving trees from
essentially the same species set and using similar phylogenetic methods.
Differences and similarities based on the two markers are discussed.
Additionally, 31 group 2 sigma factors were analyzed in combination with
the group 1 proteins in order to detect functional groupings of these
alternative sigma factors. The data suggest that promoters recognized by
the major vegetative sigma factors of eubacteria will contain sequence
motifs and spacing very similar to those for the sigma70 sigma factors of
Escherichia coli.
Copyright © 1997, American Society for Microbiology
Molecular systematic studies of eubacteria, using sigma70-type sigma factors of group 1 and group 2
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA.
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