Accelerated evolutionary rate in sulfur-oxidizing endosymbiotic bacteria associated with the mode of symbiont transmission

The nearly neutral theory of molecular evolution predicts that the rate of nucleotide substitution should accelerate in small populations at sites under low selective constraint. We examined these predictions with respect to the relative population sizes for three bacterial life histories within che...

Full description

Saved in:
Bibliographic Details
Published in:Molecular biology and evolution 1998-11, Vol.15 (11), p.1514-1523
Main Authors: Peek, A S, Vrijenhoek, R C, Gaut, B S
Format: Article
Language:English
Subjects:
Betaproteobacteria - genetics
Betaproteobacteria - metabolism
DNA, Bacterial - genetics
Evolution, Molecular
Gammaproteobacteria - genetics
Gammaproteobacteria - metabolism
Gene Transfer, Horizontal - genetics
Likelihood Functions
Mutagenesis - genetics
Nucleic Acid Conformation
Oxidation-Reduction
Phylogeny
RNA, Ribosomal, 16S - genetics
Sulfur - metabolism
Symbiosis - genetics
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The nearly neutral theory of molecular evolution predicts that the rate of nucleotide substitution should accelerate in small populations at sites under low selective constraint. We examined these predictions with respect to the relative population sizes for three bacterial life histories within chemolithoautotrophic sulfur-oxidizing bacteria: (1) free-living bacteria, (2) environmentally captured symbionts, and (3) maternally transmitted symbionts. Both relative rates of nucleotide substitution and relative ratios of loop, stem, and domain substitutions from 1,165 nt of the small-subunit 16S rDNA were consistent with expectations of the nearly neutral theory. Relative to free-living sulfur-oxidizing autotrophic bacteria, the maternally transmitted symbionts have faster substitution rates overall and also in low-constraint domains of 16S rDNA. Nucleotide substitition rates also differ between loop and stem positions. All of these findings are consistent with the predictions that these symbionts have relatively small effective population sizes. In contrast, the rates of nucleotide substitution in environmentally captured symbionts are slower, particularly in high-constraint domains, than in free-living bacteria.
ISSN:0737-4038
1537-1719
DOI:10.1093/oxfordjournals.molbev.a025879