Conjugation related costs have reduced impact on in silico plasmid persistence

Due to the important role they play in the antimicrobial resistance (AMR) crisis and in microbial evolution in general, a great deal of empirical and theoretical work is currently underway, trying to understand plasmid ecology. One of the key questions is how these often costly genetic elements persist in host populations. Here I show that when modelling plasmid population dynamics, it is not sufficient to treat them as always costly (or beneficial). I argue that conjugation related costs may be more important to plasmids in nature than they are in benign laboratory settings. Furthermore, I show that these conjugation related costs can be very severe and still not lead to extinction of a plasmid from a host population.