Frédérique Le Roux

Seeking expressions of interest from researchers abroad for a Canada Impact+ Research Chair ($1M/year × 8 + up to $6M CFI) in AI-enabled antibiotic discovery and/or AMR, phage & phage-based derivatives. Email me a short vision, CV, and 3–5 key papers. Deadline: March 10, 2026 (Intake 2: June 15).

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!

Many thanks to all those involved, including Jeffrey Liang, who stayed in our lab for several months, our own Charles Bernard and, of course, @fredoleroux.bsky.social and the usual suspects @agencerecherche.bsky.social @erc.europa.eu @cnrsbiologie.bsky.social @pasteur.fr @umontreal.ca etc

Two intensive sampling periods of oyster-associated vibrio and their phage, 4 years apart, and many surprises. Despite being washed by the Atlantic, wide tides, and vibrio (almost?) disappearing most of the year, we can find the exact same virulent phages 4 years later (down to 0 SNP)! preprint👇

Ecological constraints foster both extreme viral-host lineage stability and mobile element diversity in a marine community Phages are typically viewed as very rapidly evolving biological entities. Little is known, however, about whether and how phages can establish long-term genetic stability. We addressed this eco-evolut...

Phages evolve fast, or do they?
In oysters, some stay identical for years.
With >1,200 phages & 600 Vibrio genomes, we reveal long-term stability and new mobile elements.
Proud of this collaborative work across our teams (Roscoff-UdeM and @epcrocha.bsky.social www.biorxiv.org/cgi/content/...

Chimeric infective particles expand species boundaries in phage-inducible chromosomal island mobilization Capsid-forming PICIs (cf-PICIs) produce their own capsids and exploit phage tails from unrelated species to transfer their DNA across bacterial hosts. This tail piracy enables broad dissemination and ...

Thrilled to share our two latest papers with the @tcostalab.bsky.social
lab! In the first, we uncover a new mechanism of satellite transfer: cf-PICIs hijack tails from diverse phages to spread across species.
@imperialcollegeldn.bsky.social
www.cell.com/cell/fulltex...

Chimeric infective particles expand species boundaries in phage-inducible chromosomal island mobilization Capsid-forming PICIs (cf-PICIs) produce their own capsids and exploit phage tails from unrelated species to transfer their DNA across bacterial hosts. This tail piracy enables broad dissemination and ...

Chimeric infective particles expand species boundaries in phage-inducible chromosomal island mobilization: Cell www.cell.com/cell/fulltex...

The ecology and evolution of microbial immune systems: a look on the wild vibrio side | Philosophical Transactions of the Royal Society B: Biological Sciences Natural populations of vibrio beyond the well-studied pandemic strains of Vibrio cholerae, provide a powerful model for investigating the eco-evolutionary dynamics of microbial immune systems. Their genetic diversity, ecological versatility, ease of ...

The ecology and evolution of microbial immune systems: a look on the wild vibrio side

Phil. Trans. R. Soc. B by @fredoleroux.bsky.social

royalsocietypublishing.org/doi/10.1098/...

And thank you so much Pauline!!! It was very cool to see you again with other 'old' conference friends, looking forward to see you again @ Roscoff 2026/Monod conference/virus evolution ;-)?

SCM-CSM2025 UMontreal Conference Fourwaves - SCM-CSM2025 UMontreal Conference

and here is the link for the program: event.fourwaves.com/fr/scm-csm20...

👉 Next stop: Montréal! 🇨🇦 Thrilled to join the Canada Society of Microbiology (CSM) conference, June 17-20. Science, community, and reconnecting with old friends — can’t wait!

The study involves our‪ microbiologist @fredoleroux.bsky.social, whom we profiled in late 2023 as a new hire and Canada Excellence in Research Chair: nouvelles.umontreal.ca/en/article/2...

Allo Montreal, 11 juin –18H au café La brassée:
"Des sphères aux spirales, des extrémophiles aux probiotiques: plongez dans l’univers fascinant des bactéries ! "
Appéro- Science, qui dit mieux? #cinqascience #5ascience

commemorating pride from the clinical microbiology lab

How clonal are bacteria over time? Bacteria and archaea reproduce clonally (vertical descent), but exchange genes by recombination (horizontal transfer). Recombination allows adaptive m…

And I've written a few reviews on the subject over the years, but this one is pretty short, so why not start there ;)

www.sciencedirect.com/science/arti...

Allo Montreal, 11 juin –18H au café La brassée:
"Des sphères aux spirales, des extrémophiles aux probiotiques: plongez dans l’univers fascinant des bactéries ! "
Appéro- Science, qui dit mieux? #cinqascience #5ascience

Bacteriophages infecting an Escherichia coli bacterium. Credit: Institut Pasteur/Chantal Le Bouguénec (Pathogenic Gram-Positive Bacteria Biology Unit) and Laurent Debarbieux (Molecular Biology of the Gene in Extremophiles Unit). Imaging by Perrine Bomme, Ultrastructural Microscopy Platform. Colorization by Jean-Marc Panaud.

🧬 Bacteria fight both antibiotics and viruses with the same genetic tool: integrons!

New study (Institut Pasteur, CNRS, Université Paris Cité & Montréal): ~10% of gene cassettes may defend against phages.

🛠️ One step closer to smarter therapies.

🔗 www.pasteur.fr/en/research-...

Congratulation Mélanie, so cool story on phage defense and pathogen evolution in real life!

West African–South American pandemic Vibrio cholerae encodes multiple distinct phage defence systems - Nature Microbiology The West African–South American lineage of Vibrio cholerae contains multiple distinct anti-phage defence systems that provide resistance to various phage families, including vibriophage ICP1, a key pr...

Exciting news!! Our latest paper is out in Nat. Microbiol. @natmicrobiol.nature.com

We show that a sub-lineage of 7th pandemic V. cholerae has acquired mobile genetic elements packed with phage defense systems—rendering it multi-phage resistant 😳 ..... 1/3

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

Allo Montréal, prochain Cinq à Science, 14 mai, le microbiote intestinal par Corinne Maurice, mc Gills 🙂

Mobile integrons encode phage defense systems Integrons are bacterial genetic elements that capture, stockpile, and modulate the expression of genes encoded in integron cassettes. Mobile integrons (MIs) are borne on plasmids, acting as a vehicle ...

Have also a look at our back-to-back study for mobile integrons by Nicolas Kieffer from @jaescudero.bsky.social group !
www.science.org/doi/10.1126/...
+ a similar story in V. parahaemolyticus by @landongetz.bsky.social from @themaxwelllab.bsky.social
www.nature.com/articles/s41...

An enormous thanks for the great co-first author @eloilittner.bsky.social and for our supervisors @celineloot.bsky.social @epcrocha.bsky.social @amazeld.bsky.social @fredoleroux.bsky.social. Many thanks to all co-authors !!

On the bioinformatic side, eloilittner.bsky.social found a diverse arsenal of anti-phage defenses in SCIs. Strikingly, systems in integrons are always compact (< 3 genes), and smaller than their homologs outside integrons (likely due to cassette size constraints)

The integron of our favorite model Vibrio cholerae was mostly “dark matter” as most cassettes had no known role. We found this intriguing and cloned 88 cassettes, testing them for phage resistance. We found 16 defensive cassettes and named the systems after gallic mythology

Sedentary chromosomal integrons as biobanks of bacterial antiphage defense systems Integrons are genetic systems that drive bacterial adaptation by acquiring, expressing, and shuffling gene cassettes. While mobile integrons are well known for spreading antibiotic resistance genes, t...

White smoke, we have a new pope and also 16 new anti-phages systems in sedentary integrons (SCIs) !
In collaboration with the Rocha lab, we show in our new paper that cassettes of these large platforms encode many known anti-phage defenses, and uncovered 16 new ones.
www.science.org/doi/10.1126/...

Habemus paper! Our story on integron-encoded anti-phage defenses is now out in @science.org! 16 new systems, small versions of known ones, and a lot more in this highly-collaborative study.

Many thanks to everyone involved, especially my supervisor @epcrocha.bsky.social

bsky.app/profile/bapt...

Allo Montréal! Prochain Cinq à Science, le 14 mai, 6pm, Corinne Maurice, Mc Gill, Microbiote intestinal. #cinqascience

Pas de recul. / No retreat.
Pas de silence. / No silence.
Pas de haine chez nous. / No hate here.
🇨🇦 Liberté, justice, solidarité. / 🇨🇦 Freedom, justice, solidarity.
Résistons ensemble! ✊ / Let’s resist together! ✊
#CanadaLibre #DefendDemocracy #LoveWins

Application deadline: May 27, 2025

Launch of the 2025 postdoctoral fellowship competition The BIC is proud to launch its first Postdoctoral Fellowship competition. Applications are open from now until May 27, 2025.

🚨 Postdoc Alert!
Join my lab @ Montréal’s Faculty of Medicine via the 2025 CIB Fellowship Competition 🧬
Project: “The Paradox of Parasitism” – bioinformatics + marine parasite evolution
💸 $63,819/yr + full benefits (2 yrs)
Apply 👉 cibmontreal.ca/en/news/laun...