Molecular studies of polysaccharides from pathogenic bacteria

Bacterial exopolysaccharides (EPS) are known to protect microbial cells from a hostile environment, often by forming biofilms. Moreover, pathogens which produce EPS as a defence against the human immune system were demonstrated to be more resistant to host defence mechanisms both in vivo and in vitro. Therefore, the knowledge of EPS structures is a prerequisite to understand their role in bacterial infections. In the Bacterial Polysaccharide Laboratory the research is focussed on bacteria involved in lung infections in cystic fibrosis (CF) patients, in particular on species belonging to the Burkholderia cepacia complex (Bcc) and on Stenotrophomonas maltophilia. This project focuses on the structure-function relationship of bacterial EPS involved in infections, by studying their primary structure and correlating it with functional properties. The research described in this thesis regards three main lines: 1) The definition of the primary structure of the EPS produced by one strain of Burkholderia vietnamiensis and two clinical strains of Stenotrophomonas maltophilia; 2) The scavenging effect of cepacian, the main EPS produced by the Bcc, towards reactive oxygen species (ROS); 3) The preliminary investigation of the role of EPS from the Bcc in the formation of biofilms.