Take a ride on my journey with glycans

Maria Michela Corsaro, Department of Chemical Sciences, University of Naples Federico II, Italy

Host: Filomena Freitas, UCIBIO NOVA

 

ZOOM link: https://ucibio.pt/l/GuestSeminars

 

Abstract:

Carbohydrates encompass all the living systems. Huge work has been done by researchers from all over the world to cover all the aspects of the chemistry and biochemistry of these complex molecules. Polysaccharides have industrial applications in the paper, food, biotechnological, textile, cosmetic, and pharmaceutical industries due to their properties. Nowadays, polysaccharides represent a possible  ecological substitute for the petroleum industry, as their sources are renewable and not pollutant. In addition, they are biodegradable, usually not toxic, and their enzymatic or chemical degradation can produce biofuel together with many simple molecules, which can form industrial polymers and fine chemicals [1].

Microbial glycans can be obtained by both Gram-negative and Gram-positive bacteria cells. The lipopolysaccharides (LPSs) are the major component of the outer membrane (OM) of almost all Gram-negative bacteria and some cyanobacteria [2,3], constituting approximately 75% of the outer surface. They are endotoxin heat-stable amphiphilic molecules indispensable for the viability and survival of Gram-negative bacteria, as they heavily contribute to the structural integrity of the OM and the protection of the bacterial cell envelope [4]. Extracellular polysaccharides (also called exopolysaccharides, EPSs) are glycopolymers that can be found associated with the cell surface as a capsule (CPS) or secreted in their surrounding environment as slime.

Marine habitats represent a large and unique environment where diverse communities of bacteria perform fundamental activities for the survival of the planet’s ecosystem [5]. Ocean microorganisms account for approximately half of the primary production of organic substances on earth [6] and, among these, EPSs occupy a prominent position. Furthermore, microbes that populate extreme environments represent a renewable source of bioactive molecules.

These microorganisms generally cannot be easily cultivated in the laboratory, and their biochemistry and physiology are largely unknown. One of the greatest enigmas, however, is how these huge microbial populations can survive in these harsh conditions. Bacterial adaptation strategies involve surface carbohydrates, both LPSs and CPSs and EPSs. Our research group can establish the primary structure and the structure/function relationship of these complex macromolecules in their habitats. Our study aims to understand the role of carbohydrate structures in such energy-depleted environmental conditions and to exploit their specific properties.

My journey will touch on most of the analytical facets necessary to understand how to manage microbial glycans. In addition, some key achievements of my research group will be illustrated.

 

Short CV:

Maria Michela Corsaro is a Professor of Organic Chemistry at the Department of Chemical Sciences at the University of Naples Federico II. She earned her PhD in 1989 with a thesis about polysaccharides from plants. Her research activity has led to about 150 scientific publications in peer-reviewed international journals. She leads a research group working on carbohydrate chemistry in Naples. She is connected to many international research groups with scientific expertise spanning from microbiology to biotechnology and polymer science. Very recently she became an Associate Editor of the International Journal of Biological Macromolecules.

M. Michela Corsaro possesses well-established expertise in the isolation and structural elucidation of bacterial glycoconjugates, developed in the frame of continuing research within the last 30 years and directed to the discovery of structure/function relationships of bacterial carbohydrate-containing molecules. She reached an expert level of experience within this field, starting from the punctual characterization of oligo/polysaccharides and ending with the very recent macromolecular approach. This target has paved the way for an in-depth study of microbial carbohydrate functions. Specifically, the main focuses of her research activities are the studies of i) the structure of bacterial lipopolysaccharides (LPS) and extracellular polysaccharides (CPS and EPS), ii) the interactions between LPS and CPS, iii) the role of LPS and CPS within the bacterial environment.

During the last few years, Prof. Corsaro has applied her chemical knowledge to explore the bioactivity of EPS and LPS, with a special focus on cold environments. Key achievements of Maria Michela  Corsaro's research are the discovery of the first capsular polysaccharide with anti-freeze properties, with structural features very close to those of the well-known anti-freeze glycoproteins. Recently, she has been engaged in the purification and structural characterization of vesicle glycolipids.

 

References:

1. Barsett, H.; Ebringerovà, A.; Harding, S.E.; Heinze, T.; Hromàdkovà, Z.; Muzzarelli, C.; Muzzarelli, R.A.A.; Paulsen, B.S.; El Seoud, S.A. Polysaccharides I. Structure, Characterisation and Use, Editors: Heinze, Thomas (Ed.) 2005, Springer
2. Carillo S, Pieretti G, Bedini E et al (2014) Structural investigation of the antagonist LPS from the cyanobacterium Oscillatoria planktothrix FP1. Carbohydr Res 388:73-80.
3. Lüderitz O, Freudenberg MA, Galanos C et al (1982) Lipopolysaccharides of Gram-negative bacteria. In: Razin S, Rottem S (ed) Current Topics in Membranes and Transport, Academic Press Inc, New York, p 79-51.
4. Alexander C, Rietschel ET (2001) Bacterial lipopolysaccharides and innate immunity. J Endoxin Res 7:167-202.
5. Abreu, N.A.; Taga, M.E. (2016) Decoding molecular interactions in microbial communities. FEMS Microbiol. Rev., 40, 648-663.
6. Field, C.B.; Behrenfeld, M.J.; Randerson, J.T.; Falkowski, P. (1998) Primary production of the biosphere: integrating terrestrial and oceanic components. Science, 281, 237-40.