Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.01.230672v1?rss=1 Authors: Alonso-del Valle, A., Leon-Sampedro, R., Rodriguez-Beltran, J., DelaFuente, J., Hernandez-Garcia, M., Ruiz-Garbajosa, P., Canton, R., Pena-Miller, R., San Millan, A. Abstract: Plasmid persistence in bacterial populations is strongly influenced by the fitness effects associated with plasmid carriage. However, plasmid fitness effects in wild-type bacterial hosts remain largely unexplored. In this study, we determined the distribution of fitness effects (DFE) for the major antibiotic resistance plasmid pOXA-48 in wild-type, ecologically compatible enterobacterial isolates from the human gut microbiota. Our results show that although pOXA-48 produced an overall reduction in bacterial fitness, the DFE was dominated by quasi-neutral effects, and beneficial effects were observed in several isolates. Incorporating these data into a simple population dynamics model revealed a new set of conditions for plasmid stability in bacterial communities, with plasmid persistence increasing with bacterial diversity and becoming less dependent on conjugation. Moreover, genomic results showed a link between plasmid fitness effects and bacterial phylogeny, helping to explain pOXA-48 epidemiology. Our results provide a simple and general explanation for plasmid persistence in natural bacterial communities. Copy rights belong to original authors. Visit the link for more info