GC-Content evolution in bacterial genomes: the biased gene conversion hypothesis expands.

Area of Science:

• Evolutionary Biology
• Genomics
• Molecular Biology

Background:

• Identifying natural selection signatures in genomes requires accounting for neutral processes like mutation and drift.
• GC-Biased Gene Conversion (gBGC) is a known factor in eukaryotes, mimicking selection for high GC-content in recombining regions.
• Previous studies excluded gBGC as an explanation for GC-richness in bacteria.

Purpose of the Study:

• To investigate the presence and impact of GC-Biased Gene Conversion (gBGC) in bacterial genomes.
• To determine if gBGC can explain previously unexplained patterns in bacterial genome evolution.
• To compare the intensity of gBGC in bacteria with that observed in mammals.

Main Methods:

• Analyzing the relationship between gene GC-content and intra-genic recombination across diverse bacterial clades.
• Assessing the independence of the observed GC-enrichment pattern from selection on codon usage.
• Comparing bacterial gBGC patterns with human population data.

Main Results:

• A consistent positive correlation between gene GC-content and intra-genic recombination was found across bacterial species.
• The evolutionary force driving this pattern acts independently of selection on codon usage, potentially interfering with AU-codon selection.
• The intensity of gBGC in bacteria is comparable to that observed in mammals.

Conclusions:

• GC-Biased Gene Conversion (gBGC) is likely prevalent in most bacterial species, not just eukaryotes.
• gBGC can explain non-equilibrium base substitution patterns and gene composition heterogeneity in bacterial genomes.
• Accurate analysis of bacterial genome evolution necessitates considering gBGC as a significant evolutionary force.