Force spectroscopy was used to show that extracellular DNA (eDNA) has the pre-eminent structural role in a Micrococcus luteus (M. luteus) biofilm. The adhesive behavior of extracellular polymeric substances to a model hydrophobic surface was measured in response to their degradation by hydrolytic enzymes known for their biofilm-dispersion potential: DNaseI, protease, cellulase, and mannanase. This method of using force spectroscopy to investigate biofilm structure involved growing biofilms on a tipless cantilever and probing it against a poly(ethylene terephalate) surface, a known favourable substrate for M. luteus binding. Force retraction curves were analysed for the magnitude and number of force events occurring after treatment with each enzyme to characterise the roles that target molecules in the biofilm structure. eDNA and proteins were shown to play structural roles while polysaccharides are responsible for adhesion. Confocal microscopy was also used to measure biovolume changes of M. luteus biofilms when exposed to the various enzymes to further understand the observed effects of enzymes. DNaseI was found to be the only treatment that significantly decreased the amount of biovolume present. Only treatment with DNaseI significantly decreased the adhesive force of the model bacterium M. luteus with the surface, and furthermore this treatment almost completely eliminated any components of the biofilm maintaining the adhesion, establishing a key structural role for eDNA.

Extracellular DNA provides structural integrity to a Micrococcus luteus biofilm

2019 Fall National Meeting

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