Physiological and Genomic Effects on Stutzerimonas stutzeri After One Year of Driven Evolution

Abstract

[eng] Evolution is one of the most significant forces that drive changes in biological systems and has shaped life the way know it today. Prokaryotes are the preferred model organisms to study live evolutionary processes due to their high mutation rates and short cycles. Proof of this is Prof Lenski’s work, which has successfully studied Escherichia coli in favourable conditions on liquid media for more than 30 years (Lenski et al.,2018; Banzhaf et al.,2020 & Atolia et al.,2020). Considering that precedent, we designed an in-plate experiment with the Gammaproteobacteria Stutzerimonas stutzeri AN10 (Figure 1), formerly known as Pseudomonas stutzeri, a motile bacterium with a versatile metabolism (Lalucat et al.,2021 & Lalucat et al.,2006) and an elevated mutation rate (MartínCardona, 2009). Furthermore, it possesses a set of insertion sequences that facilitate genomic rearrangement in the cell (Christie-Oleza et al., 2008). Our experiment introduced a stressor in two independent culture lines: nutrient depletion on the slow line and required continuous motility on the fast line for one year producing differential phenotypes. Our goal was to assess the adaptations selected for each stressor. To address those questions, the phenotype and physiology of the isolates obtained at the end of the experiment were evaluated through biofilm formation, in-plate colonisation capacities, the role of the different motility mechanisms, and competition experiments. The molecular analysis involved whole-genome sequencing from selected isolates to elucidate the origins of the phenotypical variation observed. In summary, we have characterised differential phenotypes for each stressor that are consistent and persistent through time, evidencing the depth and lasting character of the modifications that surpasses gene regulation or fast response mechanisms.