Capsule acidic polysaccharides

Resistance to phagocytosis is sometimes associated with specific components of the cell wall and/or with the presence of capsules surrounding the cell wall. Classic examples of these are the M-proteins of the streptococci and the polysaccharide capsules of pneumococci. The acidic polysaccharide K-antigens of Escherichia coli and Sal typhi behave similarly, in that (i) they can mediate attachment to the intestinal epithelial cells, and (ii) they render phagocytosis more difficult. Generally, possession of an extracellular capsule will reduce the likelihood of phagocytosis. 

We chose the acidic polymer as the interior member of the capsule forming pair due to the expected compatibility with cells of acidic polysaccharides such as alginate and carboxymethyl cellulose. For this reason, droplet viscosity and, therefore, stability was improved by synthesizing the acidic polymers as higher molecular weight analogues of the corresponding polybases. 

Capsules and capsular antigens are considered to be outer envelope polymers, usually high-molecular-weight acidic polysaccharides, which surround the bacterial cell in the form of a hydrophilic gel. Polysaccharides adhering weakly to the cell are known as slime layers. 

The function of the polysaccharide capsule in inhibiting the alternative pathway is most satisfactorily and simply explained by the fact that it masks the underlying, bacterial structures (for example, tei-choic acids), which are known to be powerful activators of the alternative pathway.153-158 However, although this mechanism is no doubt... 

Although it has, to date, not been possible to identify any common structural feature among all the polysaccharide capsules of bacteria associated with the most pathogenic human disease, there is one common feature in many of them. The capsular polysaccharide of type III group B Streptococcus has terminal sialic acid residues in its structure,62,63 as do the groups B and C N. meningitidis and K1 E. coli.3 -34 The ability of terminal sialic acid residues to inhibit the activation of complement by way of the alternative pathway has been well docu-... 

The uridine diphosphate ester derivatives in a non-capsulated. Type II pneumococcus and a capsulated. Type III pneumococcus were investigated by Smith, Mills, and Harper." The capsule of the Type III pneumococcus is composed of a polysaccharide having 4-0-( 8-D-glucopyranosyluronic acid)-D-glucose as a repeating unit. n-Glucuronic acid, D-glucose, and L-rhamnose are constituents of the capsular polysaccharide of the Type II pneumococcus. 

Although polysaccharide can be recovered from the culture medium, capsular preparations are preferable. Several methods of isolating capsular polysaccharides are available. In one such method, the capsule is solubilized by leaching of cells in 30% aqueous potassium chloride. The product contains 7 % of hexuronic acid, 18% of hexose, and 31 % of pentose. Culture conditions used in the production of Cr. neoformans in capsular form have been patented. ... 

This chapter describes dental caries (tooth decay) and its causes. Sucrose and other mono- and disaccharides are metabolized to acid (lactate) by bacteria that remain in stagnation areas of the teeth. Rats and hamsters fed a 50% sucrose diet developed a caries-sensitive, predominantly gram-positive microbiota that became caries resistant when the rodents were fed penicillin (Sect. 1). Further studies identified Streptococcus mutans (S. mutans) as the etiological agent. This organism synthesizes an insoluble polysaccharide capsule that is stable and retains lactate at the enamel surface (Sect. 2). The key enzyme, glucosyl transferase, is related to salivary amylase which adheres to oral bacteria and enhances bacterial acid production. The chapter concludes with a discussion of salivary and other factors responsible for the marked variation observed in individual caries experience (Sect. 3). 

Transformation of a noncapsulated Type III strain of Pneumococcus with deoxyribonucleic acid from a fully capsulated Type I strain gave a small proportion of a new type of cells which elaborated two capsular polysaccharides (I and III) in addition to Type I transformants. In this case, bio83mthesis of Type III capsular polysaccharide was restored by utilization of uridine 5-(D-glucopyranosyluronic acid pyrophosphate) from the Type I pathway. - ... 

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