Biophysical insights into sugar-dependent medium acidification promoting YfaL protein-mediated Escherichia coli self-aggregation, biofilm formation and acid stress resistance
Résumé
The ability of bacteria to interact with their environement is crucial to form aggregates, biofilms, and develop a
collective stress resistance behavior. Despite its environmental and medical importance, bacterial aggregation is poorly
understood and mediated by few known adhesion structures. We identified here a novel surface-exposed Escherichia coli
protein, YfaL, that can self-recognize and induce bacterial autoaggregation. This process occurs only under acidic
conditions generated during E. coli growth in the presence of fermentable sugars. These findings were supported by
electrokinetic and atomic force spectroscopy measurements, which revealed changes in the electrostatic, hydrophobic,
and structural properties of YfaL upon sugar consumption. Furthermore, YfaL-mediated autoaggregation promotes biofilm
formation and enhances E. coli's resistance to acid stress. The prevalence and conservation of YfaL in environmental and
clinical E. coli suggest strong evolutionary selection for its function inside or outside the host. Overall, our results
emphasize the importance of environmental parameters such as low pH as physicochemical cues influencing bacterial
adhesins and aggregation, affecting E. coli and potentially other bacteria's resistance to environmental stress.
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