Very excited with the online publication of our modeling work on the evolution of sexual reproduction during obligate endosymbiosis: doi.org/10.1098/rstb.... The first publication of Alkmini Zania 🎉; together with Paulien Hogeweg.
@shrylishreekar.bsky.social and me wrote a commentary on Chunhui Hao's and @stuwest.bsky.social et al.'s recent paper
"Cooperation and the evolution of bacterial niche breadth"
in PNAS.
Please find our commentary here:
www.pnas.org/doi/10.1073/...
With a 135 complete, circular Pelagibacter genomes, we have answered some of the most outstanding questions about what is often considered the most abundant organism on the planet, with roughly 10 million times more individuals in the ocean than stars in the universe. Check out our preprint.
Now out in AEM @asm.org! 🎉🧪
*High school student-isolated mutants 👉🏻 novel genetic causes of biofilm-associated adaptations
*We learn how diversity arises quickly and is maintained
*EvolvingSTEM enables scalable research in classrooms & promotes scientific literacy
journals.asm.org/eprint/FBU9M...
On the architecture and evolution of prokaryotic multicellularity
Preprint from @escolizzi.bsky.social
www.authorea.com/doi/full/10....
What started out as a student project has grown over the last 2 years into a full-fledged review!
So many thanks to @escolizzi.bsky.social for leading this multicellular effort and sharing your evolutionary wisdom with us 🫶🏻🦠
Phd students Genna Sohl and Arthur Schubert led this work, which began over a year ago at the @spp2389.bsky.social meeting, when Thorsten Mascher asked me to work with them.
Link: bit.ly/4ta06Gq
4/4
We hope this review helps conceptualise multicellularity on prokaryotic terms - and highlights just how much remains to understand about its evolution (which is a lot!).
3/4
tree of bacterial and archaeal life, showing that each major clade has reported examples of multicellular organisations, including biofilms, filaments, fruiting bodies, motile aggregates, etc.
Spoiler: Prokaryotic multicellularity is pervasive and incredibly diverse.
Filaments, floating aggregates, motile collectives, biofilms... we have barely scratched the surface (pun intended) of how they organise multicellular life.
And that organisation is intimately tied to how they evolve.
2/4
An overview of bacterial multicellular formations: biofilms, filaments, free-floating aggregates, motile collectives and fruiting bodies. For each form, we mention an analogous eukaryotic multicellular form (respectively animal epitelia, filaments in fungi, Volvox, Dictyostelium/social animals, Dictyostelium and other slime moulds)
How common is multicellularity in bacteria? And archaea?
And how does it evolve?
We wrote a short review "On the architecture and evolution of prokaryotic multicellularity".
Preprint link: bit.ly/4ta06Gq
Sharing and comments are much appreciated.
1/4
Now out in its final form, our investigation of how Pseudomonas aeruginosa manages resources to permit ongoing adaptations to environment during starvation:
journals.asm.org/doi/10.1128/... Congrats to first author @findunmun1.bsky.social, and co-authors Claudia Hemsley and Elize Ambulte.
Do you know a paper describing evolution of (enhanced) biofilm formation upon phage exposure?
Thus not an experiment where biofilm is used for EE, but EE of a bacterial population leading to protection against phage via biofilm matrix/aggregation/etc
Asking for a friend's teaching lecture
Phd Position alert 🚨
Join our project ASTRAfun (Adaptation and Starship Traffic in Root-Associated fungi), in which we will use computational models to unveil the hidden dynamics of fungal evolution.
It’s not going to be just regular fun. It’s going to ASTRAfun. 🤓
www.uu.nl/en/organisat...
New pre-print from us showing how biophysical traits like cell surface hydrophobicity dictate Pseudomonas aeruginosa aggregate architecture & shield cooperators from cheaters. May have relevance for understanding social evolution in chronic infections. 🧬🧫
doi.org/10.64898/202...
The take-home message is: Multicellular reproduction can be a rewired unicellular program.
Please see the pre-print: bit.ly/4rr2mHU
Plenty more detail in the paper, plus some nice extra results.
End.
So to recap:
➡️ Early developmental programs evolve from the ecological dynamics of the unicellular ancestor.
➡️ Depending on resource distribution, our model yields different multicellular life cycles, including some that reproduce via unicellular propagules.
Why this matters: it suggests a general route to early development.
New multicellular traits can appear by co-opting existing regulation, repurposing when/where effector genes act.
In our model, the coupling of cell state (behaviour) and adhesion is what gets co-opted to generate propagules.
Re-playing the evolutionary steps from the unicellular ancestors to a multicellular group that reproduces through propagules: the adhesion mechanism of the ancestor becomes co-opted (incorporated) in the multicellular life-cycle.
Answer: co-option is pervasive.
The mechanism that makes propagules in the multicellular state—low adhesion during the dividing state—is co-opted from the ancestral unicellular life cycle, and repurposed during the transition to multicellularity to make offspring.
We then wondered how propagules evolved.
Are they constructed from scratch? Do they co-opt pieces of the unicellular ancestor?
Because it’s a computational model, we have the full fossil record. We can literally rewind evolution and watch the steps, generation by generation.
Following a single cell within a cluster - as it transition from high adhesion and migratory to down-regulating adhesion and dividing - thus forming a propagule. The cell then divides and the two offspring adhere to each other and migrate as a small offspring cluster.
Mechanistically, propagule formation is driven by a regulatory switch: cells stick strongly while migrating, but once fed they reduce adhesion and switch into division. Dividing cells then peel off as propagules (follow the white border cell).
When food patches are near, only unicellular solutions evolve: by not sticking cells disperse better and reach resources faster.
At intermediate patchiness, multicellular groups produce propagules. The group migrates rapidly towards food, and propagules colonise new patches—best of both worlds.
When resources are more homogeneously distributed, the system evolves unicellular solutions, when resources are patchy and far apart, multicellular life cycles evolve, including propagules and for high resource heterogeneity group splitting.
Why do different life cycles evolve?
Well, cells survive if they eat. So resource distribution is the key parameter.
When food is far apart, adhesion enables collective migration (see: bit.ly/4s9YIUa). So selection favours groups that reproduce by splitting—each daughter already functional.
And it’s not just this outcome.
From the same ingredients, we get a whole zoo of possible solutions: unicellular life cycles, single-cell and multicellular propagules (in the video), and large groups that split by tearing themselves apart.
Over generations, cells evolve adhesion and form multicellular groups.
But then: how does a group reproduce? In many runs, groups release single-cell propagules that detach and grow into new groups.
Single-cell propagules are everywhere in multicellular life—and here they evolve spontaneously 😎
In the model, each cell carries a gene regulatory network: a small circuit controlling when to forage, divide, and stick to other cells.
Mutations during division rewire the network, so these behaviours evolve. Cells that do not eat die.
That’s it! Mutation + selection. Can development evolve?
With @alefern.bsky.social and @renskevroomans.bsky.social, we built a model to fully recapitulate the transition.
But we didn’t want to pre-suppose any particular life cycle — we wanted them to evolve from scratch.
So we started simple: cells move (red) towards food (brown), and divide (blue).
Multicellularity makes reproduction... weird.
Single cells reproduce by division 🦠➡️🦠🦠
But multicellular life often reproduces via developmental programs: gene regulation, cell differentiation, etc.
Where do the first multicellular programs come from, before dedicated developmental machinery exists?
Curious about the origin of development during the transition to multicellularity?
A very belated preprint alert: bit.ly/4rr2mHU
Reproduction emerges from ecological interactions at the onset of multicellularity.
A short 🧵 with lots of videos...
Why this matters: it suggests a general route to early development.
New multicellular traits can appear by co-opting existing regulation, repurposing when/where effector genes act.
In our model, the coupling of cell state (behaviour) and adhesion is what gets co-opted to generate propagules.
In case you missed it: our review titled "Spatial structure: shaping the ecology and evolution of microbial communities" is out! 🚨
Let me hit you with some highlights on why spatial structure matters. (and why you should care!)
Sharing is appreciated 🙏 🧵👇
doi.org/10.1093/fems...
