Force spectroscopy was used to show that extracellular DNA (eDNA) has the pre-eminent structural role in a biofilm. The adhesive behavior of extracellular polymeric substances to poly(ethylene terephthalate), 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. Only treatment with DNaseI significantly decreased the adhesive force of the model bacterium Micrococcus 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. ASSOCIATED CONTENT Supporting Information. Contact angle methods, results of biofilm coated silicon wafer after enzyme treatments, fluorescence image of biofilm-coated cantilever, and forcedistance control curves showing poly-lysine contacting a PET substrate. This material is available free of charge via the Internet at http://pubs.acs.org.
Attachment assays
of a
Pseudomonas
isolate to
fused silica slides showed that treatment with DNaseI significantly
inhibited cellular adsorption, which was restored upon DNA treatment.
These assays confirmed the important role of extracellular DNA (eDNA)
adsorption to a surface. To investigate the eDNA adsorption mechanism,
single-molecule force spectroscopy (SMFS) was used to measure the
adsorption of eDNA to silicon surfaces in the presence of different
concentrations of sodium and calcium ions. SMFS reveals that the work
of adhesion required to remove calcium-bound eDNA from the silicon
oxide surface is substantially greater than that for sodium. Molecular
dynamics simulations were also performed, and here, it was shown that
the energy gain in eDNA adsorption to a silicon oxide surface in the
presence of calcium ions is small and much less than that in the presence
of sodium. The simulations show that the length scales involved in
eDNA adsorption are less in the presence of sodium ions than those
in the presence of calcium. In the presence of calcium, eDNA is pushed
above the surface cations, whereas in the presence of sodium ions,
short-range interactions with the surface dominate. Moreover, SMFS
data show that increasing [Ca
2+
] from 1 to 10 mM increases
the adsorption of the cations to the silicon oxide surface and consequently
enhances the Stern layer, which in turn increases the length scale
associated with eDNA adsorption.
Direct glycan-glycan interactions are increasingly implicated in survival and pathogenicity of bacteria. Here, we show that they can be exploited by protozoan parasites in their insect hosts. Force spectroscopy revealed...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.