An alternative infrared spectroscopy assay for the quantification of polysaccharides in bacterial samples.

The ability of bacteria to produce extracellular polysaccharides has been regarded as an indication of biofilm-forming capacity. Therefore, the determination of the sugar content in bacterial samples becomes a significant parameter. The colorimetric methods currently used are rather sensitive to the nature of the sugars and therefore require knowledge of the sugar types present in the samples.

Permeability and thermodynamics study of quaternary ammonium surfactants-phosphocholine vesicle system.

Quaternary ammonium compounds (QACs) are recognized as membrane active agents widely used as biocides. The main purpose of this work was to investigate the influence of the QAC head group and acyl chain length on their permeability-perturbing power and on their affinity for lipidic membranes. Permeability perturbations were assessed by measuring the release of calcein entrapped inside vesicles.

Solute size effects on the diffusion in biofilms of Streptococcus mutans.

The diffusion of poly(ethylene glycol) (PEG) (MW varying between 200 and 10,000), and of three different types of micelles was examined in Streptococcus mutans biofilms using infrared spectroscopy. PEGs were used because they show limited interactions with biological materials and their weight can be selected in order to cover a wide range of size. The study showed that a considerable fraction at the base of the biofilm was not accessible to the diffusing solute molecules and this inaccessible fraction was very dependent on the size of the diffusing molecules.

Characterization of the diffusion of polyethylene glycol in Streptococcus mutans biofilms by Raman microspectroscopy.

We used Raman microspectroscopy to investigate in situ the spatial distribution of the biomass in Streptococcus mutans biofilms. We used the CH stretching band to probe the organic matter and the area of the OH stretching band as an internal intensity standard, the biofilms being highly hydrated. The size of the biofilm regions that were mapped was 300 x 300 microm.