Simonetta Gribaldo

Widespread and intron-rich mirusviruses are predicted to reproduce in nuclei of unicellular eukaryotes - Nature Microbiology Environmental metagenomic explorations show that Mirusviricota lineages lack essential replication and transcription genes and contain spliceosomal introns, suggesting nuclear reproduction.

Check out our latest paper on mirusviruses, one of the most remarkable new groups of protist viruses - extremely diverse, carry lots of spliceosomal introns (including new homing introns) and are at the evolutionary crossroads between tailed phages and herpesviruses! www.nature.com/articles/s41...

Structural basis of lipopolysaccharide assembly by the outer membrane translocon holo-complex Nature Communications - The asymmetric distribution of lipopolysaccharide (LPS) on the surface of the bacterial outer membrane is essential and crucial for antibiotic resistance. Here, authors...

rdcu.be/eRxNf here our new study on the characterization of the lipopolysaccharide holotranslocon, LptDE and the newly identified subunits LptM and LptY. Great collaboration with @fronzeslab.bsky.social @pstansfeld.bsky.social @JulienMarcoux @YvesQuentin

Thanks Alex, updating in progress ;-) @babebe.bsky.social

Incredible science coming out from our lab. Congrats @kivenson.bsky.social 🎉

Introgression impacts the evolution of bacteria, but species borders are rarely fuzzy Nature Communications - It is commonly thought that bacterial species borders tend to be fuzzy, due to frequent exchange of DNA. Here, Diop et al. quantify the patterns of gene flow between core...

Our latest paper is out with @adiop.bsky.social and @gmdouglas.bsky.social. We analyzed the extent of homologous recombination between bacterial species (introgression) and how it affects species borders (it can vary a lot depending on the approach used to classify species!). rdcu.be/eQAMf

The diderm cell envelope is not a stack of layers but a unified scaffold of Inner Membrane–Peptidoglycan–Outer Membrane.
We discuss how tethering the OM to the PG in E. coli preserves integrity — and extend the concept across diderm bacteria.
Curr Opin Microbiol: doi.org/10.1016/j.mi...
#microsky 🔬

We are looking for a PhD student to work on an exciting plastid endosymbiosis in microbial eukaryotes. This position involves sampling, exciting microscopy such as CARDFISH, ExM and FIBSEM, single-cell transcriptomics and more. #protistsonsky 1/2

Archaeal cells whose DNA has been stained with a blue dye. Zoomed-in images of mutant cells that display chromosome segregation defects.

High-resolution images of DNA-protein complexes obtained with atomic force microscopy. Upon binding, the protein bridges distant sites, forming loops.

📢 Interested in #chromosomes 🧬 & #archaea thriving at the edge of life? PhD project in York,UK on how archaea pass on their genome to daughter cells.Friendly supervisors: me, @steve-quinn-lab.bsky.social & @georgerheath.bsky.social

www.findaphd.com/phds/project...
📅 January 7, 2026
Please RP🙏thx!

Methanobrevibacter smithii

Curious about the top methane-maker in your gut? Meet this month's featured microbe and find out! 🦠💨🔥 in @cp-trendsmicrobiol.bsky.social #archaeasky
@sgribaldo.bsky.social @pasteur.fr
🔗 Full article linked in reply👇
www.sciencedirect.com/science/arti...

Une piste prometteuse pour augmenter l’efficacité des antibiotiques Les aminosides sont des antibiotiques efficaces contre de très nombreuses bactéries telles que Escherichia coli, Pseudomonas aeruginosa ou Staphylococcus aureus. Mais jusqu’à présent, personne ne sava...

🦠💊 L’Institut @pasteur.fr vient de publier un communiqué de presse sur nos récents travaux, qui décrivent une nouvelle piste pour augmenter l’efficacité des antibiotiques. #Pasteurdon #Recherche #Science #AMR

Merci à toutes celles et ceux qui ont contribué.

📘 English version coming soon!

Molecular dissection of Class A PBP function uncovers novel features of the non-canonical Clostridioides difficile divisome complex Author summary Bacterial cell division is an ancient and essential process, but our molecular understanding of this process is primarily based on studies in a select few model systems. Recent work fou...

Excited to share my latest postdoctoral work in the Shen Lab at Tufts! In this study, we follow up on an exciting finding by former grad student @shailab.bsky.social that C diff uses its Class A PBP (PBP1) to drive cell division (unlike previously studied bacteria)! journals.plos.org/plosgenetics...

Lab’s first paper is out!! We show the first structures of #Asgard #chromatin by #cryo-EM 🧬❄️
Asgard histones form closed and open hypernucleosomes. Closed are conserved across #Archaea, while open resemble eukaryotic H3–H4 octasomes and are Asgard-specific. More here: www.cell.com/molecular-ce...

Pan-modification profiling facilitates a cross-evolutionary dissection of the thermoregulated ribosomal epitranscriptome Pan-Mod-seq enables systematic, multi-modification mapping of rRNA across life. Applying it to diverse organisms reveals that hyperthermophiles dynamically install stabilizing modifications to support...

How to become a "hot RNA" 🌡️? The answers were kindly provided by hyperthermophilic archaea: rRNA modifications are key! Check out this new publication presenting pan-modification profiling of the epitranscriptome. www.cell.com/cell/fulltex.... (1/3)

🚀🔬 Announcing #IMS2026 at @itqbnova.bsky.social! We're assembling a #LifeSciences #Microscopy symposium packed with ✨ speakers and 🧑‍🔬 workshops. All about imaging cells with photons, electrons and AI! If you love microscopy, you need to be here. Join us on March 19!
ims2026.itqbnovacommunity.org

🦠🔬🤖🧑‍💻 #mAIcrobe is out! With @pinholab.bsky.social's lab, we launched an open-source framework for high-throughput bacterial image analysis. By rockstars A. Brito & B. Saraiva et al, making #DeepLearning for phenotyping accessible! Easy to use, plus model training

📜 www.biorxiv.org/content/10.1...

Chromosome segregation dynamics during the cell cycle of Staphylococcus aureus - Nature Communications Our understanding of chromosome organization and dynamics in spherical bacteria, such as Staphylococcus aureus, remains limited. Here, the authors show that chromosome replication and cell division cycles are not synchronized in S. aureus, with cells exhibiting two segregated origins of replication at the start of the cell cycle.

Chromosome replication and cell division cycles are not synchronized in Staphylococcus aureus, with cells exhibiting two segregated origins of replication at the start of the cell cycle

#bacteria #microbiology

Serial innovations by Asgard archaea shaped the DNA replication machinery of the early eukaryotic ancestor - Nature Ecology & Evolution Phylogenetic and biochemical analyses show a diversity of components of the DNA replication machinery in different Asgard archaea that contributed to the eukaryotic DNA replication machinery.

Glad to share our paper out today @NatureEcoEvo: “Serial innovations by Asgard archaea shaped the DNA replication machinery of the early eukaryotic ancestor”. www.nature.com/articles/s41... #microsky #archaeasky

I am excited to share my PhD work on head-direction cells recorded in the wild, now published in @science.org, where we recorded neurons in bats flying outdoors on an island.

doi.org/10.1126/sci...

With @ray-neuro.bsky.social, Shir Maimon, Liora Las, Nachum Ulanovsky and many others

WE ARE BACK!!! Archaea Power Hour will return this coming WEDNESDAY, Oct. 22nd at 10AM EST/4PM CET. Check your email for the Zoom link (coming soon) or register here: forms.gle/6QvCjHH2H4pxro…. Take a look at the exciting talks we have planned to kick off our fall seminar series:

Viruses and virus satellites of haloarchaea and their nanosized DPANN symbionts reveal intricate nested interactions - Nature Microbiology An exploration of the viromes of haloarchaea and their ultra-small DPANN symbionts reveals plasmid-derived satellites of viruses from both archaeal groups, highlighting the complexity of nested symbio...

Our work on viruses and virus satellites of haloarchaea and their DPANN symbionts is out today in Nature Microbiology!
@mkrupovic.bsky.social @deemteam.bsky.social @anagtz.bsky.social
www.nature.com/articles/s41...

Our work on ribosome hibernation in archaea is out!
We identified Hib, a new hibernation factor broadly distributed across archaea.
Check out the preprint 👉 biorxiv.org/content/10.1101/2025.10.11.676729v1
(1/🧵)

Excited to share our preprint led by Carlos Voogdt et al

We developed new genetic tools & genome-wide libraries for species of the Bacteroidales order; constructed saturated barcoded transposon libraries in key representatives of three genera.
www.biorxiv.org/content/10.1...

A new family of ribosome hibernation factors in Archaea Ribosome hibernation preserves translation machinery during stress, yet its mechanisms in Archaea remain poorly defined. Here we identify Hib, a previously unrecognized family of archaeal hibernation factors. Genetic, structural and biochemical analyses show that Hib binds ribosomal subunits, blocking the mRNA channel and tRNA sites to inactivate translation. Deletion of hib in Thermococcus barophilus delays recovery from stationary phase and reduces 70S ribosome pools, establishing its role in ribosome preservation. Hib displays a unique modular architecture, combining a bacterial-like HPF module with tandem CBS domains. Cryo-EM structures reveal conformational heterogeneity of Hib:ribosome complexes, consistent with dynamic engagement, and the CBS-containing N-terminal domain binds adenine nucleotides, suggesting a link between hibernation and energy status. These findings define Hib as a key archaeal hibernation factor and provide a framework for understanding ribosome dormancy and adaptation across all domains of life. ### Competing Interest Statement The authors have declared no competing interest. Agence Nationale de la Recherche, https://ror.org/00rbzpz17, ANR-25-CE12-4161

A new family of ribosome hibernation factors in Archaea | bioRxiv https://www.biorxiv.org/content/10.1101/2025.10.11.676729v1?rss=1

Pretty excited to share our new preprint!
Non-photosynthetic Plastid Replacement by a Primary Plastid in the Making
www.biorxiv.org/content/10.1...

Versatile NTP recognition and domain fusions expand the functional repertoire of the ParB-CTPase fold beyond chromosome segregation Nucleotide triphosphate (NTP)-dependent molecular switches regulate essential cellular processes by cycling between active and inactive states through nucleotide binding and hydrolysis. These mechanis...

new preprint from our group & Antoine Hocher: www.biorxiv.org/content/10.1...
A fantastic collaboration with Antoine, with Jovana Kaljevic' initiated the collaboration and drives the project.

Phage lysis protein LysM acts as a wedge to block MurJ conformational changes Structural analysis reveals how a phage protein blocks a lipid II flippase to prevent bacterial cell wall synthesis.

www.science.org/doi/10.1126/...

#phagesky #phage

Role of endopeptidases in lateral cell wall expansion in Escherichia coli Peptidoglycan, the major constituent of bacterial cell walls, is a giant macromolecule made of glycan strands cross-linked by short peptides, which pr…

Proud of our new study out in @cp-cellreports.bsky.social!
Using E. coli lacking all 8 endopeptidases, we provide direct evidence that peptidoglycan expansion during elongation requires ED-mediated insertion of one glycan strand at a time. This can be performed by MepS, MepM, MepH and PBP7 #microsky

A photo of a Nobel medal

BREAKING: The Nobel Prize in Physiology or Medicine has been awarded jointly to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi "for their discoveries concerning peripheral immune tolerance"

Stay tuned for more.
#NobelPrize

Wonderful pair of papers by Augustinas Silale and Ben Berks on the diversity of BAM complexes.

Most diderm bacteria lack all BAM accessory previously identified in E. coli.

These two papers show a whole new set of accessory proteins in Bacteroidota.

How many more BAMs is there out there?
👁️👃🏼👁️

Structure of a distinct β-barrel assembly machinery complex in the Bacteroidota - Nature Microbiology Structural and functional characterization of the β-barrel assembly machinery complex in Bacteroidota reveals a distinct, seven-component complex with a large extracellular domain that may enable β-barrel–surface lipoprotein complex assembly.

Our paper on the Bacteroidota BAM complex is out in @natmicrobiol.nature.com! With @madejmar.bsky.social

We found that BAM in Bacteroides and Porphyromonas gingivalis has a distinct architecture from BAM in Proteobacteria.

doi.org/10.1038/s415...