Preventing biofilms of clinically relevant organisms using bacteriophage

Structure-function relationships in microbial exopolysaccharides.

Publisher Summary This chapter surveys current knowledge of the production and synthesis of microbial exopolysaccharides Although the emphasis is on bacterial polymers, relevant information is included on similar products from yeasts, fungi, and other eukaryotes The chapter covers specific aspects such as capsule synthesis, regulation of biosynthesis, and industrial applications of the products The chapter explores that numerous microorganisms produce exopolysaccharides—that is, polysaccharides found outside the cell wall, either attached to it in the form of capsules or secreted into the extracellular environment in the form of slime Such polymers vary considerably in their chemical structures The three groups of exopolysaccharides, which have been most studied are those produced by Enterobacter aerogenes, Escherichia coli and Streptococcus (Dipfococcus) pneumoniae The chapter considers that exopolysaccharides belongs to five distinct groups: (1) dextrans and related polysaccharides, (2) group of polymers, (3) number of microorganisms produce extracellular homopolysaccharides from any of several carbon substrates, (4) heteropolysaccharides, and (5) bacterial alginate

Biosynthesis of Microbial Exopolysaccharides

Bacteriophage for three representative strains of Gram-negative biofilm bacteria have proved to be of widespread occurrence. Lytic bacteriophage have been isolated from local sewage for the bacterium 1.15, an exopolysaccharide (EPS)-producing pseudomonad found originally as a component of biofilms in a local river, and for two Enterobacter agglomerans strains from industrial biofilms. Representative examples of all three bacteriophage possess a relatively low burst size and on solid media, exhibit very large plaques surrounded by a wide halo (5-20 mm) indicative of polysaccharide depolymerase action. The bacteriophage are thus similar to other viruses for EPS-producing bacteria in inducing the synthesis of enzymes degrading the polymers which occlude the bacterial cell surface. In each preparation, the polysaccharase activity was associated both with sedimented phage particles and with the supernate of bacterial lysates. The enzymes have been partially purified and used to prepare polysaccharide digests in which the major products from each polysaccharide are the presumed repeat units of the polymers or oligomers of these. The soluble phage enzymes each degrade their substrate by acting as endo-glycanohydrolases. The phage and their associated enzymes thus provide very useful highly specific tools for studies of biofilms incorporating the bacterial host strains. Their potential applications in studies on bacterial biofilms are discussed.

Bacteriophage and associated polysaccharide depolymerases: Novel tools for study of bacterial biofilms

The ubiquitous nature of bacteria in the environment, and the role they play in infectious disease has been one of the most extensively researched areas in biomedical science. It has led to tremendous scientific breakthroughs aimed at eradicating a myriad of diseases and improving the overall quality of life. However, within the past 20–30 years, there has been an ACHTUNGTRENNUNGincreased understanding that bacterial biofilms are a major factor in the morbidity and mortality of most infectious diseases. This is significant because bacterial biofilms are resistant to common therapeutic approaches that would eliminate their free-floating (planktonic) counterparts. Biofilms are described as surface-associated communities of microorganisms encased in a protective extracellular matrix. Approximately 80 % of the world’s microbial biomass resides in the biofilm state, and the National Institutes of Health (NIH) estimates that upwards of 75 % of microbial infections that occur in the human body are underpinned by the formation and persistence of biofilms. Common diseases associated with the formation of biofilms include lung infections of individuals who suffer from cystic fibrosis (CF), burn wound infections, otitis media, bacterial endocarditis, and tooth decay (Table 1). 6] Additionally, the

Controlling bacterial biofilms.

Several strains of bacteriophage have been isolated that induce the formation of a polysaccharide hydrolase after infection of Klebsiella aerogenes type 54 [A3(S1)]. The action of this enzyme on polysaccharide solutions was to decrease their viscosity and increase their reducing value. These effects were associated with the release of two oligosaccharides (O1 and O2) from the polysaccharide. These two substances are not identical with any of the four oligosaccharides isolated from autohydrolysates. The two enzymically isolated fractions have been tentatively identified as tetrasaccharides, and oligosaccharide O2 is probably an acetylated version of oligosaccharide O1. This latter oligosaccharide differs in some way, still unknown, from the tetrasaccharide cellobiosylglucuronosylfucose found in acid hydrolysates of the slime polysaccharide. The enzyme is limited in its activity to the polysaccharide excreted by the A3 strain of K. aerogenes type 54 or by similar strains. It is also active on the polysaccharides altered by acid or alkaline treatment. The enzyme has optimum activity at pH6·5. A study of the products released by enzyme action has shown it to be a fucosidase splitting the fucosylglucose linkages found in the intact polysaccharide.

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IW Sutherland

Papers

Phage-induced fucosidases hydrolysing the exopolysaccharide of Klebsiella arogenes type 54 [A3(S1)].