The view from my new workplace :)

Can't possibly be happier to be working on phage satellites with @jmouradesousa.bsky.social , @epcrocha.bsky.social and the team!

Throughout this time I've also been very lucky to meet fantastic friends and colleagues that made everything so much better🧡

An important chapter of my life and career comes to an end - now I'm ready and excited for the next!

Thank you to my PhD supervisor Edze Westra for everything - it has been great working with you! I'll always keep treasure of what I learnt from you and your team over these years!

My official PhD graduation last month was the closing step of an incredible journey, marking the end of my time in Cornwall!

So how does MADS work? We propose the following model
mad1 as putative system regulator
mad2:mad5 to form the N6 Meth complex
mad3-4 predicted nucleases
mad6 could regulate the system via phosphorylation
MAD7 may help recognize unmethylated DNA for loading into the MAD8 nuclease

MADS + CRISPR -> strong, durable protection vs phage
Single resistance: phages can easily bypass each defense
Dual resistance: Acr-phages must first acquire methylation to bypass MADS to successfully cooperate to overcome CRISPR, but this process is constrained by CRISPR activity

mathematical modelling and experiments indicate MADS escaping phages, in the presence of CRISPR-Cas (black) only emerge at very high phage density.
Such high starting phage density is not required to support phage persistence when CRISPR-Cas is absent (yellow)

PacBio sequences of escape phages showed methylation of this site. The WT strain is methylated as well, but not the ΔMADS

Phages can easily escape MADS only when CRISPR is absent (yellow). During infection of the WT strain (black, MADS+CRISPR) phages cannot persist, falling below detection limit, unlike during infection of ΔMADS (orange, only CRISPR) and of the double-KO (green, no MADS, no CRISPR)

We found variations in the gene compositions of MADS in different genera - this could be due to the existence of subtypes/ genetic divergence or degenerate systems

Within this hotspot, in other strains we also found systems seemingly akin to MADS, which we describe as MADS-like

MADS is found in 0.3% of the RefSeq genomes, only in Bacteria, and is phylogenetically widespread, occurring in Gram+ and Gram-.
It is located within a genomic hotspot with conserved boundaries

MADS protects also against plasmids and other phages

Assays in solid and liquid media show MADS protects against phage infection, with ~100 fold increase in EOP and reduced bacterial growth when MADS is absent

Using Tn5 mutagenesis we detected MADS as an 8 gene system, with domains shared with other systems, which is common.
These include:
- N6 methyltransferase domain
- serine/threonine kinase domain
- RM specificity subunit
- Dnd-like proteins
- DNA binding and nuclease domains

How we found it: we wanted to study phage DMS3 and Type IE CRISPR-Cas interactions. Despite phage has functional anti-CRISPR gene, we saw no phage epidemics (even at high MOI) or lysogenization (unlike for the pos ctrl PA14)
so we hypothesized another system may be involved 👀

A Sunday afternoon in Cornwall