Bacterial biofilm mechanical properties persist upon antibiotic treatment and survive cell death
Résumé
Bacteria living on surfaces form heterogeneous three-dimensional
consortia known as biofilms, where they exhibit many specific properties one
of which is an increased tolerance to antibiotics. Biofilms are maintained by a
polymeric network and display physical properties similar to that of complex
fluids. In this work, we address the question of the impact of antibiotic treatment
on the physical properties of biofilms based on recently developed tools enabling
the in situ mapping of biofilm local mechanical properties at the micron scale.
This approach takes into account the material heterogeneity and reveals the
spatial distribution of all the small changes that may occur in the structure. With
an Escherichia coli biofilm, we demonstrate using in situ fluorescent labeling
that the two antibiotics ofloxacin and ticarcillin—targeting DNA replication
and membrane assembly, respectively—induced no detectable alteration of the
biofilm mechanical properties while they killed the vast majority of the cells. In
parallel, we show that a proteolytic enzyme that cleaves extracellular proteins
into short peptides, but does not alter bacterial viability in the biofilm, clearly
affects the mechanical properties of the biofilm structure, inducing a significant
increase of the material compliance. We conclude that conventional biofilm control strategy relying on the use of biocides targeting cells is missing a key target since biofilm structural integrity is preserved. This is expected to
efficiently promote biofilm resilience, especially in the presence of persister
cells. In contrast, the targeting of polymer network cross-links—among which
extracellular proteins emerge as major players—offers a promising route for the
development of rational multi-target strategies to fight against biofilms.
Origine : Publication financée par une institution
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