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Gene essentiality determines chromosome organisation in bacteria
Eduardo P C Rocha1, Antoine Danchin
1Unité Génétique des Génomes Bactériens, Institut Pasteur, 28, rue du Dr Roux, 75724 Paris Cedex 15, France. erocha@abi.snv.jussieu.fr
Nucleic Acids Research
|November 7, 2003
Summary
Essentiality, not gene expression, dictates gene placement on bacterial DNA strands. Essential genes are preferentially located on the leading strand, influencing genome evolution and stability across diverse bacteria.
Area of Science:
- Genomics and Evolutionary Biology
- Molecular Biology
- Bioinformatics
Background:
- Gene distribution between leading and lagging DNA strands is crucial for replication and genome stability.
- Previous studies in Escherichia coli and Bacillus subtilis suggested essentiality, not expressivity, drives this distribution.
- The evolutionary extent and selective constraints of this phenomenon across diverse bacterial lineages remained largely uninvestigated.
Purpose of the Study:
- To investigate the role of gene essentiality in gene distribution across replicating DNA strands in a broader range of bacteria.
- To compare gene distribution patterns between essential and non-essential genes, including highly expressed ones.
- To assess the impact of essentiality assignment methods and explore potential biases in obligatory intracellular bacteria.
Main Methods:
- Comparative genomic analysis of low G+C firmicutes, gamma-proteobacteria, and all sequenced bacterial genomes.
- Inference of gene essentiality using homology-based methods.
- Statistical analysis to compare gene frequencies on leading vs. lagging strands and assess conservation.
Main Results:
- Essential genes are significantly more frequent on the leading DNA strand compared to non-essential genes, even highly expressed ones.
- A smaller bias towards the leading strand was observed in obligatory intracellular bacteria, potentially due to challenges in essentiality assignment.
- Essential genes exhibit higher conservation on the leading strand, suggesting selection for this positioning and constraints on chromosomal rearrangements.
Conclusions:
- Gene essentiality is a fundamental driver of gene distribution on the leading strand across most bacterial genomes.
- Selection for positioning essential genes on the leading strand likely imposes constraints on genome evolution and chromosomal structure.
- The findings highlight the interplay between replication, essentiality, and genome organization in bacterial evolution.