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G+C3 structuring along the genome: a common feature in prokaryotes.
1Laboratoire de Biométrie et Biologie Evolutive, Université Claude Bernard, Lyon 1, Villeurbanne, France.
Molecular Biology and Evolution
|March 26, 2003
Summary
Prokaryotic genomes show structured gene content, influenced by chromosomal position, not just selection or mutation. This genomic organization impacts evolutionary rate and may skew lateral gene transfer predictions.
Area of Science:
- Genomics
- Evolutionary Biology
- Molecular Biology
Background:
- Gene nucleotide content heterogeneity in prokaryotes is often attributed to selection, mutation, and lateral gene transfer.
- Existing models overlook chromosomal organization, replication, and folding constraints on gene evolution.
Purpose of the Study:
- To analyze the structuring of codon usage measures along bacterial genomes.
- To investigate the influence of genomic position on gene base content and evolutionary pressures.
Main Methods:
- Analysis of codon usage patterns across completely sequenced bacterial genomes.
- Examination of gene base composition relative to chromosomal location, particularly near the replication terminus.
Main Results:
- Most bacterial genomes exhibit significant structural organization in gene base content.
- A common pattern of A+T enrichment near the replication terminus was observed across many bacterial phyla.
- This A+T enrichment correlates with increased evolutionary rates in some species.
Conclusions:
- Chromosomal structural constraints significantly influence gene evolution in bacteria.
- The inherent structuring of bacterial genomes may lead to overestimation of lateral gene transfer rates when using codon composition.
- Genomic position and structural constraints are critical factors in understanding prokaryotic genome evolution.