25] Isolation and biochemical characterization of extracellular polymeric substances from Pseudomonas aeruginosa

Abstract

This chapter discusses that Biofilms of Pseudomonas aeruginosa have been intensively studied during the last decade. Pseudomonas aeruginosa offers several advantages as a model organism in biofilm research. This gram-negative bacterium is well characterized with respect to its molecular genetics, biochemistry, and physiology; it is also of hygienic relevance as an opportunistic pathogen, because biofilms harboring this bacterium in technical water systems and on medical devices may be a source of human infections. The extracellular polymeric substances (EPS) of P. aeruginosa predominantly consist of different polysaccharides and proteins. Mucoid variants of P. aeruginosa are characterized by an overproduction of the viscous exopolysaccharide alginate, resulting in the production of large slimy colonies, when the bacteria are cultivated overnight on common agar-based media. Alginates from P. aeruginosa are high molecular weight unbranched copolymers consisting of (1→ 4)-linked uronic acid residues of β-D-mannuronate and α-L-guluronate. The formation of biofilms is regarded as part of a natural “life cycle” of mucoid P. aeruginosa. Alginates represent major components of the EPS of mucoid P. aeruginosa and have been implicated in the development as well as the maintenance of the mechanical stability of biofilms formed by P aeruginosa on living and abiotic surfaces. In this chapter, methods of isolation and biochemical characterization are described for both whole EPS and alginate from mucoid strains of P. aeruginosa grown as a confluent bacterial lawn on agar media as simple in vitro model systems for bacterial biofilms.