Bacteria capsular polysaccharide activity

Capsular polysaccharides are actively involved in the mediation of complement, in that they are able to suppress the activation of the immediate, alternative-pathway mechanism, thus forcing the immune system to use the classical pathway this is an important factor in the virulence of bacteria (see Section VI,1). 

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-... 

All tailed phages have evolved tailspike and fiber proteins for efficient virus-host-interactions. These specialized adhesions mediate the recognition and attachment to the bacterial surface and constitute the key determinants for host specificity. Interestingly, many spikes and fibers are composed of homotrimeric complexes which remain stable even in the presence of sodium dodecyl sulfate (SDS) [12, 14, 30-34], Several phages have developed tailspike proteins with an enzymatic activity in order to penetrate the thick layer of lipopolysaccharides or capsular polysaccharides of many pathogenic bacteria. These capsule-specific depolymerases (hydrolases or lyases) are required to gain access to and to fix the phage at the bacterial outer membrane [13, 14, 35-38]. 

Transformation and Transduction. Transformation factors of bacteria have produced important proof for the genetic role of DNA. Of some bacteria, e.g., the Pneumococci, different strains are known which produce different capsular material. The material (a polysaccharide cf. Chapt. XVII-7) must be regarded as one of the hereditary properties, just like hair coloration of mammals. It is possible to convert (to transform) bacteria of one type (e.g. type II) to another (e.g. type III) by treating them under certain conditions with an extract of tyjie III The active factor in the extract was prepared in pure form by Avery (1944) it is high molecular weight DNA. The assumption is that transformation is a transplantation of a gene. In the host bacterium, the transplanted nucleic acid, used in the process of transformation, acquires the capacity to induce characteristics—here the synthesis of type-specific capsular material. It also acquires in the host the capacity for identical replication, since the very same transformation factor can be isolated in quantity from a new harvest of transformed bacteria. 

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