iiinova — where your digital self keeps evolving

Benoit Pons

@benoitjpons.bsky.social

332 followers 258 following 18 posts

Lecturer in bacterial genomics at Université de Toulouse Research in phage-bacteria co-evolution at LMGM-CBI @cbitoulouse.bsky.social he/him

Posts Replies Media

Benoit Pons @benoitjpons.bsky.social · 04/09/2025

Finally, we used flux cytometry to confirm that the elongated phenotype was linked with SOS response induction.

Flow cytometry graph showing that a subpopulation of CRISPR-immune bacteria is elongated and fluorescent (thus showing a SOS response activation) while surface-based resistant bacteria are homogeneously non-elongated non-fluorescent.

120

Benoit Pons @benoitjpons.bsky.social · 04/09/2025

However, we noticed some heterogeneity in the population, with some CRISPR-immune bacteria stalling and suffering from elongation, particularly at high phage doses, which is consistent with this second hypothesis

Cumulative probability of division curves. Surface-based resistant bacteria are not affected by the presence of phage and the median time between two division is the same for all treatments. CRISPR-resistant bacteria median division time is slightly increased at low phage dose and significantly increased at high phage dose

Microfluidics image displaying bacteria of several different sizes. The one on the right hand side is elongated (8 times longer than a bacteria that just completed division)

121

Benoit Pons @benoitjpons.bsky.social · 04/09/2025

Our first hypothesis was that at high phage dose, surface-based resistance offered more protection than CRISPR-immunity. However, we showed that both types of defences offer a similar, almost perfect protection against phages regardless of the phage dose.

Survival curves showing that both CRISPR-immune and surface-based resistant bacteria do not die from phage, regardless of the dose used

110

Benoit Pons @benoitjpons.bsky.social · 04/09/2025

While CRISPR-Cas system inability to fully prevent phage gene expression seemed to play a role, it was still unclear what was causing the apparent CRISPR-Cas fitness cost at high phage doses. Here we investigated two hypotheses by using a microfluidics set-up to follow single bacteria in microscopy.

Typical image from a microfluidics experiment. One large channel at the bottom is linked to several tiny perpendicular channels in which bacteria are growing

110