Bacterial gene 5′ ends have unusual mutation rates that can mislead tests of selection

Description

Sofia Radrizzani, Juan Rivas-Santisteban, Namshik Han, and Laurence Hurst warn that mutation patterns can fake evidence of selection in bacteria in a 2025 paper. The start of bacterial genes shows oddly slow evolution at silent sites, long read as selection favoring certain letters. The slow zone, though, extends far past the first ten codons where the selection story applies.

The team tested three explanations in Escherichia coli and a Bacillus species. Overlapping genes did not explain it, and neither did a slow-start translation ramp. Mutation accumulation data told the real story: the gene start simply mutates more slowly, about half the body rate at the first codons, rising steadily after. Letter composition explains part of it. Slow evolution, they conclude, is not proof of selection.

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Source: https://europepmc.org/articles/PMC12725619