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A phylogenomic study of endosymbiotic bacteria
Björn Canbäck1, Ivica Tamas, Siv G E Andersson
1Department of Molecular Evolution, Evolutionary Biology Center, University of Uppsala, Uppsala, Sweden.
Molecular Biology and Evolution
|March 12, 2004
Summary
Endosymbiotic bacteria like Buchnera aphidicola and Wigglesworthia glossinidia show accelerated evolution. Host-level selection, not gene transfer, explains their genomic changes and gene retention.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genomics
Background:
- Aphid endosymbionts (Buchnera aphidicola) and tsetse fly symbionts (Wigglesworthia glossinidia) are derived from free-living gamma-Proteobacteria.
- Understanding the evolutionary trajectory of these endosymbionts is crucial for comprehending host-symbiont co-evolution.
Purpose of the Study:
- To estimate the acceleration of sequence evolution in endosymbiont genomes.
- To investigate the factors driving genomic changes in bacterial endosymbionts.
- To clarify the role of lateral gene transfer versus other mechanisms in endosymbiont evolution.
Main Methods:
- Phylogenomic analysis of gamma-Proteobacteria.
- Examination of tree topologies using highly conserved genes.
- Analysis of substitution rates and nucleotide patterns.
Main Results:
- Endosymbiont genomes exhibit accelerated sequence evolution compared to their free-living relatives.
- Deviant tree topologies are attributed to high substitution rates and biased nucleotide patterns, not lateral gene transfer.
- Gene-specific evolutionary rates correlate with host metabolic dependencies.
Conclusions:
- Host-level selection plays a significant role in retarding gene loss and slowing sequence evolution in endosymbionts.
- The genomic evolution of endosymbiotic bacteria is shaped by a complex interplay of intrinsic factors and host-imposed selective pressures.