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This large-scale study of nearly 4,000 bacterial genomes reveals that short overlaps between adjacent genes are evolutionarily flexible features rather than highly conserved structures, with frequent gains and losses occurring throughout bacterial lineages. The analysis found no strong functional bias favoring overlaps for genes encoding interacting proteins, though a modest association exists with metabolically linked genes. The results challenge assumptions about the functional significance of gene overlaps versus simple genomic proximity.
Why it matters
Understanding how bacterial genes are organized and whether overlaps serve specific functional purposes has implications for predicting gene regulation, metabolic pathway organization, and interpreting genomic data. The findings suggest that genomic proximity may be more important than actual overlap for gene coordination in bacteria.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Background Short overlaps of adjacent genes are widespread in bacterial genomes and have been proposed to contribute to coordinated gene expression through mechanisms such as translational coupling and ribosome re-initiation. However, their evolutionary dynamics and functional associations have been studied either in relatively small datasets or for individual taxonomic groups. Here, we performed a large-scale comparative analysis of bacterial gene overlaps to characterize their prevalence, structural diversity, evolutionary dynamics, and functional associations. We surveyed 3,998 representative bacterial genomes for short overlaps and analyzed a curated set of orthologous gene-pair clusters to reconstruct the evolutionary history of overlap gain and loss using ancestral-state inference. Results We confirmed that short overlaps are dominated by a small number of canonical configurations, while a substantial subset of orthologous clusters contained multiple overlap lengths or sequence motifs, indicating evolutionary flexibility. Reconstruction of ancestral states yielded repeated gains and losses of overlap within the same orthologous gene-pair lineages. Among clusters in which both states were sufficiently represented, we found no overall bias toward either overlap gain or loss. Finally, analyses of functional associations found no consistent enrichment of overlapping gene pairs among genes encoding interacting protein subunits, compared to closely spaced non-overlapping gene pairs. In contrast, metabolic linkage showed a modest positive association with overlap, although the magnitude of this association depended on the distance threshold used to define non-overlapping neighbors. Conclusions These results identify short bacterial gene overlaps as evolutionarily labile features of gene organization rather than strongly conserved genomic states and emphasize the importance of distinguishing overlap from close genomic proximity when considering their functional significance.
Source: Short gene overlaps in bacterial genomes: evolutionary dynamics and functional associations