Generation of mutation hotspots in ageing bacterial colonies

Speaker: Morten Nørholm, Center for Biosustainability, DTU
Host: Professor Kresten Lindorff-Larsen, Section for Biomolecular Sciences

Abstract
The majority of living cells exist in a quiescent, non-dividing state while they age and keep adapting to environmental changes. Exactly how this adaptation occurs has long been discussed, but not yet deciphered. Over a period of two months, we isolated on ageing bacterial colonies outgrowing mutants able to use a new carbon source, and sequenced their genomes. This allowed us to uncover exquisite details on the molecular mechanism behind their adaptation: most mutations were located in just a few hotspots in the genome and over time, mutations increasingly originated from 8-oxo-guanosine, formed exclusively on the transcribed strand. Our work provides strong support for retromutagenesis as a general process creating adaptive mutations during ageing.