The research programme coordinated by Dr. Paola Cescutti is focussed on the investigation of bacterial polysaccharides both for their structural and conformational characteristics and for their impact on bacterial life. Recently, most of the research efforts were devoted to the characterization of polysaccharides produced in bacterial biofilms and to their interaction with other molecules, like quorum sensing ones. Among the experimental methodologies used particularly relevant are: chromatographic techniques, gas-chromatography coupled to MS, NMR spectroscopy, ESI mass spectrometry.
These studies are carried out on different opportunistic bacterial species with focus on those belonging to the Burkholderia cepacia Complex and Klebsiella pneumoniae.
She also collaborates with industrial partners for the chemical analysis of glycoconjugate vaccines.
All the activities within this programme are organized in two lines of research:
Structure determination of bacterial extracellular polysaccharides
Being localized around bacterial cells, extracellular polysaccharides primarily interact with the environment. Their structure is therefore modulated to protect bacteria against external threats and to interact with a variety of different molecular agents. Understanding their structure and the way they interact is important to design possible antibacterial strategies.
The investigations are focussed on species of the Burkholderia cepacia complex, involved in serious lung infections in cystic fibrosis patients, and on multi drug resistant (MDR) species, like Klebsiella pneumoniae.
The polysaccharide primary structure determination is achieved by wet chemistry (alditol acetates analysis, methylation analysis, site-specific degradation, enzyme depolymerization) followed by analysis and by bi-dimensional NMR and ESI mass spectrometry.
Exopolysaccharide conformation and morphology are investigated by different spectroscopic techniques (CD, fluorescence) and modern microscopy, like AFM.
Bacterial biofilm composition and structure
Bacterial biofilm formation is a major problem in infections and is an important virulence factor. When imbedded in biofilms, bacterial colonies exhibit high tolerance to environmental stress, including increased resistance to antibiotics as well as components of the host immune system. Understanding the biophysical and biochemical constraints which play a critical role in biofilm architecture could constitute a major advance in developing novel anti-infection therapy routes based on biofilm disruption, and aimed at avoiding the induction of antibiotic resistance in bacteria, an issue of specific interest for the major national and international health agencies.
Biofilms produced by species of the Burkholderia cepacia complex (BCC) and Klebsiella pneumoniae are obtained in different conditions and on different growth media. The biofilm matrix is analysed for its polysaccharidic content and the identity of the extracted exopolysaccharides is established resorting to the deep knowledge of exopolysaccharides produced by the same species in planktonic conditions. Although polysaccharides are usually water soluble, within the biofilm matrix they interact with themselves and other molecules generating an insoluble gel-like network. These interactions are investigated with a variety of techniques to understand the factors which stabilize the biofilm scaffold and to envisage possible biofilm disruption strategies.
Recently, Dr. Cescutti has been funded by the NIH (USA, P.I. Prof. J.W. Brady) to investigate the biofilm polysaccharides of Burkholderia multivorans and their interactions with other molecules, like antibiotics and quorum sensing compounds.
The research group actively collaborates with several national and international collegues:
Dr. Francesca Micoli (GSK Vaccines Institute for Global Health (GVGH) S.r.l.): polysaccharide structure for glycoconjugate vaccines preparation.
Prof. Tim Tolker-Nielsen (University of Copenhagen, Denmark): biofilm composition and structure.
Prof. Neil Ravenscroft (Cape Town University, South Africa): polysaccharide structure .
Prof. Michelle Kuttel (Cape Town University, South Africa): polysaccharide modelling.
Prof. John W. Brady (Cornell University, Ithaca, USA): modelling of biofilm matrix.
Prof. Blaženka Kos (University of Zagreb): polysaccharides from Lactobacillus species.
Prof. Anja Klančnik (University of Ljubljana): surface saccharides produced by food-borne pathogens.
