Morphological investigations of the polysaccharide extracted from biofilm produced by Burkholderia multivorans strain C1576

Microbial communities often experience a collective way of life, known as biofilm, where bacterial cells are embedded in a gel-like matrix that confers protection against external threats. It is generally accepted that polysaccharides constitute the main structural component of the biofilm matrix. Due to the huge variety of repeating unit composing the bacterial polysaccharides, different 3D biofilm matrix can be generated. The structural properties of the exopolysaccharide (Epol) recovered from the biofilm matrix formed by Burkholderia multivorans strain C1576 were investigated. The repeating unit of the Epol C1576 is characterized by the presence of Rha, a 6-deoxy sugar, which displays a less polar character than other common monosaccharides. In addition, 25% of the Rha residues are methylated, thus producing less polar segments in the polysaccharide backbone. The experimental investigations, carried out by using AFM, both in dried and liquid state, and TEM showed that the Epol C1576 forms compact structures characterized by a globular morphology, confirming the ability of Epol C1576 to self-aggregate. Computer modelling of Epol C1576 3D conformation was carried out to assess the flexibility of the polymer backbone and it demonstrated that a polysaccharide segment was able to collapse into a compact structure which remained almost constant during the simulation time. This study demonstrated the polysaccharide ability to form folded compact structures that are expected to affect the overall biofilm matrix architecture.