Biofilms
represent the dominant microbial lifestyle in nature.
These complex microbial communities in which bacteria are embedded
in a self-produced protective polymeric extracellular matrix, display
an enhanced resistance to antimicrobials and thus represent a major
health challenge. Although nanoparticles have proven to be effective
against bacteria, the interactions between nanoparticles and the polymeric
biofilm matrix are still unclear. In this work, silver nanoparticles
(AgNPs) were used on mature biofilms formed by the pathogen Vibrio cholerae, and their effects on the biofilm
microstructure were evaluated. Bacteria cells within mature biofilms
showed an increased tolerance to AgNPs, with their elimination requiring
a concentration nine times higher than planktonic cells. Mutant strains
not able to form a pellicle biofilm were four times more susceptible
to AgNPs than the wild-type strain forming a strong biofilm. Moreover,
electron microscopy analysis revealed that AgNPs interacted with the
extracellular matrix components and disrupted its microstructure.
Finally, two major proteins, Bap1 and RbmA, appeared to mediate the
biofilm bacterial resistance to AgNPs. This work highlights the role
of the polymeric biofilm matrix composition in resistance to AgNPs.
It underlines how crucial it is to understand and characterize the
interactions between nanoparticles and the biofilm matrix, in order
to design appropriate metallic nanoparticles efficient against bacterial
biofilms.
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