Description
Experimental evolution approaches have been essential for understanding evolutionary mechanisms in viruses, bacteria, and eukaryotes. However, our knowledge of evolutionary dynamics of strictly host-dependent bacteria is still largely based on comparative genomics of closely related species. In order to bridge this gap, our laboratory has been conducting a series of evolution experiments using chlamydial symbionts with their amoeba hosts. The phylum Chlamydiae is comprised exclusively of bacteria with an obligate intracellular lifestyle. Their associations with eukaryotic hosts are remarkably diverse: They are major pathogens of many animals and occur ubiquitously as protist symbionts.We have established a LTEE between replicate Protochlamydia amoebophila populations in their natural Acanthamoeba host under two temperatures for ca. 500 generations (38 months). The main aim is to improve our understanding of the evolutionary dynamics and genomic/molecular basis of the intracellular lifestyle of chlamydiae. By carrying out pool sequencing, coupled with variant detection, we have observed various genomic adaptations. The substitution rate was surprisingly similar to those of free-living microbes, with a significant increase at 30°C. Clones with a strongly elevated mutation rate emerged after 180 generations. Non-synonymous substitutions were more frequent at 30°C, indicating a higher level of positive selection. By comparing infectivity of ancestral and evolved populations, those at 30°C exhibited reduced virulence, possibly as a tradeoff to survive at this temperature. Furthermore, we have also carried out RNA sequencing comparing the transcriptomes of the ancestral culture and a culture evolved at 30°C, so as to assess how long-term evolution at this raised temperature has altered the bacterial expression profile. In summary, we were able to track evolutionary dynamics of a chlamydia symbiont within its protected intracellular niche. Our approach provides novel and unique insights into evolutionary dynamics and adaptations at the genomic and phenotypic levels with respect to elevated temperature.| Period | 2018 |
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| Event title | Evolution 2018 |
| Event type | Conference |
| Location | Montpellier, FranceShow on map |