Followed by more interesting science about phages by @sultannazir.bsky.social

Thanks, Bram! Excited for our next project ✨

Here is the link to the preprint: www.biorxiv.org/content/10.1...

15/15

You can find an interactive version of our individual-based model here: sultannazir.github.io/bacteria_pro...

14/15

By attributing the evolution of gene-phage association to features of the phage lifecycle such as prophage induction regulation and virion dispersal, we help explain what sets apart prophages from other MGEs in terms of the cargo genes they carry.

13/15

Based on these findings, we propose a dispersal hypothesis: Costly gene-phage associations can evolve when phage-mediated dispersal increases the mixing of carrier and non-carrier genotypes, thereby amplifying selection for the gene in a spatially structured population.

12/15

Emergence of host immune response could also weaken the selection pressure acting on virulent mutants. Thus, virulence genes may naturally experience weak selection within the host environment, making them more likely to rely on phage-mediated dispersal more than MGEs with limited dispersal.

11/15

Weak selection is key for non-carrier regions to persist, allowing the benefit of dispersal to take effect.

Most virulence genes are expressed extracellularly, sharing their benefits with other non-carrier cells.

10/15

Why? In a structured population, selection acts locally - where carriers meet non-carriers. When the gene is phage-encoded, it can disperse via virions, reaching gene-free regions more effectively. This increases its effective rate of selection compared to the chromosomal gene.

9/15

Result 2: Within-population spatial structure increases the probability of a chromosomal gene evolving to be phage-encoded under two conditions:
1️⃣ Weaker selection pressure
2️⃣ Higher virion diffusion rate

8/15

Since prophage induction is often triggered by environmental factors, this suggests that virulence genes are linked to prophages whose induction rates are higher in the host environment.

7/15

Why? Positive correlation in gene expression & prophage induction between populations connected by migration causes a net influx of non-carrier uninfected cells into the host environment. This creates a selection pressure for the gene to become mobile via prophages.

6/15