Structure-function relationship of polysaccharides produced by opportunistic pathogens

Although the elimination of this lateral chain produces a marked lowering of the cepacian viscosity probably due to loss in aggregation ability, the search of different enzymes able to cleave the EPS backbone into oligosaccharides is still active. The fourth topic of the research focused on the interactions between different bacterial EPSs and three antimicrobial peptides, belonging to the cathelicidin family of primate's innate immune system, to investigate the possible EPSs protective role towards bacterial cells. The experiments involved EPSs produced by Pseudomonas aeruginosa, Inquilinus limosus and clinical isolates of the Burkholderia cepacia complex. The inhibition of the peptides activity was assessed by minimum inhibitory concentration assays on a reference Escherichia coli strain in the presence and in the absence of EPSs. The complex formation between peptides and EPSs was investigated by means of CD, fluorescence spectroscopy and AFM. As a result, a model was proposed where peptides with a ?-helical conformation interact with the EPSs backbone through electrostatic and non-covalent interactions. The last issue of the research involved the capsular polysaccharide produced by Neisseria meningitidis group A; this CPS is used to develop a protein conjugate vaccine by Prof. N. Ravenscroft (Dept. of Chemistry, Univ. of Cape Town). He observed that the derivatisation process, necessary prior to protein conjugation, yielded less product, in terms of protein-conjugate, than expected, and he thought that this was due to CPS aggregation in th