Katrin Hammerschmidt

Given that clonal biofilms of single bacterial species rapidly diversify into niche specialists, how do biofilms of multiple species evolve?
A 🧵 featuring new collaborative pubs:
1. www.biorxiv.org/content/10.6...
2. www.nature.com/articles/s41...

Final version @nature.com of our paper describing unconventional multicellular development in a choanoflagellate inhabiting an extreme environment. A ton of new data since the first @biorxivpreprint.bsky.social preprint (which we've kept updating).

A brief 🧵 (carried over from the old place)

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...

Resurrected nitrogenases recapitulate canonical N-isotope biosignatures over two billion years - Nature Communications The study shows that nitrogenase enzymes have maintained stable isotope signatures over billions of years, revealing how ancient microbes shaped Earth’s nitrogen cycle and offering a new experimental ...

Our new paper, out today! We resurrected ancient nitrogenases first used by life on Earth 3 billion years ago. We combined synthetic biology and geology & validated their chemical #biosignature in rocks that helps reveal ancient life on Earth!(and beyond!)

Link: www.nature.com/articles/s41...

A New Classification Framework to Understand Evolutionary Transitions in Individuality Classifying biological entities based on whether and how the two fundamental aspects physiological and evolutionary components are represented yields six types of structural organization. The resulti...

New paper by Saskia Wilmsen and me just came out BioEssays:

A new classification framework to understand evolutionary transitions in individuality

Please find the OA paper here:

onlinelibrary.wiley.com/doi/10.1002/...

This is a beautiful paper examining the molecular genetics of facultative multicellularity in a marine black yeast.

I also love that they figure out the ecological context for the behavior (MC form when in sponges, where there are nutrients, & uni when starving!).

www.nature.com/articles/s41...

Bottleneck size drives the evolution of cooperative traits in an aggregative multicellular myxobacterium Population bottlenecks shape the evolution of cooperative traits in Myxococcus xanthus through life cycle trade-offs. This study shows that stringent bottlenecks favor growth and sporulation, while re...

Very cool paper by Jyotsna Kalathera et al. from @iamsamayp.bsky.social 's-lab on

Bottleneck size drives the evolution of
cooperative traits in an aggregative multicellular
myxobacterium

just out @plosbiology.org

Congratulations to all coauthors.

journals.plos.org/plosbiology/...

Cooperation is a universal feature of complex systems, from the origins of life and microbiomes to societies. What universal patterns can be found in these systems? Here's our new @pnas.org paper. @jordipinero.bsky.social @artemyte.bsky.social @sfiscience.bsky.social www.pnas.org/doi/epdf/10....

The changing roles of Escherichia coli Nature Microbiology - Richard Lenski traces the legacy of Escherichia coli and how science is evolving to use this model organism in new ways.

"The changing roles of Escherichia coli" -- a short essay by yours truly.

rdcu.be/eVtXT

in 2013, Elio was so fascinated by the 'heterologous multicellularity' of 𝘊𝘩𝘭𝘰𝘳𝘰𝘤𝘩𝘳𝘰𝘮𝘢𝘵𝘪𝘶𝘮 𝘢𝘨𝘨𝘳𝘦𝘨𝘢𝘵𝘶𝘮 that he chose a cross-section to celebrate STC's 10th anniversary 🙂
👉 smallthingsconsidered.blog/schaechter/2...
#MicroSky

🚨 What if evolution is the ”law”… and networks are the machines that do the work?

In this paper (just published) I try to formalize how living systems are non-equilibrium, information-processing, adaptive matter. With a great biological flavor! 🧪🌐🌍🧬🦠

👉 iopscience.iop.org/article/10.1...

🧵 1/

Co-option of an ancestral peptidase controls developmental patterning in multicellular cyanobacteria Developmental biology

How do simple cells make complex patterns? We discovered a key piece in cyanobacteria—an ancient enzyme repurposed to activate a pattern-forming signal. A conserved signaling strategy, showing how nature reuses tools to build multicellularity. www.cell.com/iscience/ful...

Summer school:<br> Evolutionary Biology in Guarda Information about the annual summer school Evolutionary Biology in Guarda

The 2026 Guarda Summer Course in Evolutionary Biology is now accepting applications. Amazing place, amazing course, amazing opportunity for early grad students.

tb.ethz.ch/education/gu...

The fitness costs of reproductive specialization scale inversely with organismal size The evolution of reproductive specialization represents a fundamental innovation in multicellular life, yet the conditions favoring its evolution remain poorly understood. Here, we develop a populatio...

1/28 New preprint up, which I think is the best theoretical idea I've ever had. We asked a simple question: what are the costs of investment into non-reproductive somatic cells? Turns out these costs decrease with the *logarithm* of organism size!

www.biorxiv.org/content/10.6...

I am very excited to announce that a fully funded PhD position is available in my group.

Topic: Synergistic coevolution in mono-specific and multi-species microbial consortia

Please RT or forward this information to interested candidates.

Deadline: 11.01.26

More info:

shorturl.at/f1TuF

@kostchristian.bsky.social has an open PhD position as a part of #SPP2389 !
#microsky #mevosky

Very proud that @gauravathreya.bsky.social's brilliant work based on his Master's thesis is out as his first paper in @asn-amnat.bsky.social. Interested in host-symbiont interdependence, eukaryogenesis, evolutionary transitions in individuality, and some great theory to back it?...check out the🧵👇

Evolutionary repurposing of a DNA segregation machinery into a cytoskeletal system controlling cyanobacterial cell shape Bacteria, despite their diversity, use conserved cytoskeletal systems for their intracellular organization. In unicellular bacteria, the ParMRC DNA partitioning apparatus is well known for forming act...

One of the most exciting discoveries from our lab so far is now online as a preprint!

Read a story on how the ParMR and Min systems started to collaborate to create the CorMR cytoskeleton, which now controls cell shape in multicellular cyanobacteria:
www.biorxiv.org/content/10.1...

How does agency change as life evolves from single cells to complex bodies? This review by Stuart Newman and colleagues examines the surprising roles of development, microbes, and even cancer in reshaping what organisms can do. @multicellgenome.bsky.social www.journals.uchicago.edu/doi/pdf/10.1...

1/27 We have a new paper out! Turns out that snowflake yeast have been hiding a secret from us - they've evolved a (very!) crude circulatory system. Not with blood vessels or a heart, but through spontaneous fluid flows powered by their metabolism. 🧪🔬

www.science.org/doi/full/10....

We loved hearing @khammerschmidt.bsky.social talk about evolution at the #MultiBac2025 conference this January - check out the @asm.org report on the origins of early microbial life!

Happy to have been part of EVOLUTION & MECHANISMS GOVERNING MULTICELLULARITY—one of 3 workshops behind @asm.org’s new report. Big questions, great conversations—looking back on origins of microbial life and what lies ahead. Highly recommended read: asm.org/reports/earl...
#MicroSky #MEvoSky #EvoSky

iron toxicity model

New preprint: eukaryotic origins! 🥁

We propose that iron -not oxygen- may have delayed the rise of complex life. Our model reframes the “oxygen delay” puzzle: the gap between atmospheric O2 and early eukaryotic fossils may reflect iron-mediated stress, not for O2:

www.biorxiv.org/content/10.1...

Abstract submission extended to 1 July – Submit your work now!

Genetic Predisposition Toward Multicellularity in Chlamydomonas reinhardtii Abstract. The evolution from unicellular to multicellular organisms facilitates further phenotypic innovations, notably cellular differentiation. Multiple

Kimberly Chen, a former postdoc in my lab, has published a new article in Genome Biology and Evolution. Selection on mixed populations of Chlamydomonas resulted in the evolution of multicellular structures, all from 2 of 10 founder strains. www.linkedin.com/in/kimberly-...
doi.org/10.1093/gbe/...

This is still open for another week or so! Please apply :)

#multicellularity lovers: the website for the EMBO workshop in multicellularity is live. Barcelona is waiting for you! #protistsonsky

Check out our latest work on the evolution of animal genome regulation out today in @nature.com. Nicely summarized below by @ianakim.bsky.social.
www.nature.com/articles/s41...

This is a major output from our ERC-StG project Evocellmap @erc.europa.eu at @crg.eu

Check out this amazing segment on Pittsburgh's WTAE about our EvolvingSTEM program. 🙏🏻 to anchor Shannon Perrine for telling our story and showcasing how we engage students grades 6-12 to learn w/ authentic experiments. Teachers and students see themselves as scientists! #SaveNSF #SupportNIH

Mutualism breakdown underpins evolutionary rescue in an obligate cross-feeding bacterial consortium - Nature Communications Rapid genetic adaptation to environmental change, or evolutionary rescue, can be constrained by a less adaptable mutualistic partner. Here, the authors explore evolutionary rescue in an obligate mutua...

1/ In our new paper, we explored whether obligate mutualisms can survive abrupt stress via evolutionary rescue.

We found that evolutionary rescue is possible—but it comes at the cost of mutualism. @jfriedman.bsky.social

#microsky #evosky #mevosky