PT  - JOURNAL ARTICLE
AU  - Gemma G. R. Murray
AU  - Andrew J. Balmer
AU  - Josephine Herbert
AU  - Nazreen F. Hadijirin
AU  - Caroline L. Kemp
AU  - Marta Matuszewska
AU  - Sebastian Bruchmann
AU  - A. S. Md. Mukarram Hossain
AU  - Marcelo Gottschalk
AU  - A. W. (Dan) Tucker
AU  - Eric Miller
AU  - Lucy A. Weinert
TI  - Mutation rate dynamics reflect ecological change in an emerging zoonotic pathogen
AID  - 10.1101/2021.04.12.439332
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.04.12.439332
4099  - http://biorxiv.org/content/early/2021/10/08/2021.04.12.439332.short
4100  - http://biorxiv.org/content/early/2021/10/08/2021.04.12.439332.full
AB  - While mutation is often deleterious, it can also be adaptive. Mutation rates vary both within and between bacterial species, and understanding what drives this variation is essential for understanding the evolutionary dynamics of bacterial populations. In this study we investigate two factors that are predicted to influence the trade-off between the costs and benefits of mutation: ecology and genome size. To investigate the relationship between these factors and mutation rate we conducted mutation accumulation experiments on eight strains of the emerging zoonotic pathogen Streptococcus suis. Natural variation within this species allows us to compare tonsil carriage and invasive disease isolates, from both more and less pathogenic populations, with a wide range of genome sizes. We find that invasive disease isolates have repeatedly evolved mutation rates that are higher than those of closely related carriage isolates, regardless of variation in genome size. Independent of this variation in overall rate, we also observe a stronger bias towards G/C to A/T mutations in isolates from more pathogenic populations, whose genomes tend to be smaller and more AT-rich. Our results suggest that ecology is a stronger correlate of mutation rate than genome size over these timescales, and that transitions to invasive disease are consistently accompanied by rapid increases in mutation rate. These results shed light on the impact ecology can have on the adaptive potential of bacterial pathogens.Competing Interest StatementThe authors have declared no competing interest.