![]() ![]() The biosynthesis and surface expression have been extensively studied with representatives of group II capsular polysaccharides. All capsular polysaccharides are chromosomally determined: those of group I close to his and those of group II close to serA. coli are divided into two groups, which differ in chemistry, biochemistry, and genetic organization. Bacterial capsules consist of acidic polysaccharides, which are made up from oligosaccharide repeating units. Strains with such capsules (e.g., K1 or K5) are very virulent. In some cases, capsules are not or only poorly immunogenic, as a result of structural relationship or identity with host material. This effect is generally transient and overcome by capsule-specific antibodies in the immune phase of the host defense. They interfere with the action of complement and phagocytes. The capsules are important virulence determinants, which enable the pathogenic bacteria to evade or counteract the unspecific host defense during the early (preimmune) phase of infection. Changes associated with cellular aging in chronic infections could contribute to the remarkable capacity of this fungus to persist in tissues by generating phenotypically and antigenically different capsules.Įscherichia coli may cause intestinal or extraintestinal infections. Our results establish that cryptococcal capsules are highly dynamic structures that change dramatically with chronological aging under prolonged stationary-phase growth conditions. Remarkably, chronological aging under stationary-phase growth conditions was associated with the expression of α-1,3-glucans in the capsule, indicating a new structural capsular component. Changes in capsular properties were paralleled by changes in PS molecular mass and density, as well as modified antigenic density and antiphagocytic properties. To understand how chronological age could impact the cryptococcal capsule properties, we compared the elastic properties, permeabilities, zeta potentials, and glycosidic compositions of capsules from young and old cells and found significant differences in all parameters measured. neoformansis a polysaccharide (PS) capsule. ![]() ![]() Although O-Ag capsule-deficient mutants did not exhibit reduced virulence in a murine model of acute infection,in vitroresults indicate that the O-Ag capsule may function to modify the antigenic nature of the bacterial surface, warranting additional investigation of a potential role of the structure in pathogenesis.ĪBSTRACTDoes the age of a microbial cell affect its virulence factors? To our knowledge, this question has not been addressed previously, but the answer is of great relevance for chronic infections where microbial cells persist and age in hosts.Cryptococcus neoformansis an encapsulated human-pathogenic fungus notorious for causing chronic infections where cells of variable age persist in tissue. Furthermore, O-Ag capsule-deficient mutants produced exclusively phase I flagellin (FliC). Western blot analysis and confocal microscopy revealed that O-Ag capsule-deficient mutants demonstrate reduced resistance to killing by human serum. Loss of O-Ag capsule production did not alter bacterial growth or production of LPS. To test this hypothesis, O-Ag capsule-deficient mutants were constructed, and the loss of O-Ag capsular surface expression was confirmed through microscopy and immunoblotting. While much of thein vivoinnate immune resistance ofSalmonella entericaserovar Typhimurium is attributed to the high-molecular-weight LPS, we hypothesized that the O-Ag capsule may enhance this resistance by diminishing surface expression of pathogen-associated molecular patterns, such as flagella, and increasing resistance to host immune molecules. Previous studies on the O-Ag capsule of salmonellae have focused primarily on its role in bacterial surface attachment and chronic infection however, the potential effects of the O-Ag capsule on acute pathogenesis have yet to be investigated. Capsular polysaccharides are known virulence factors of many bacterial pathogens, facilitating evasion of immune recognition and systemic dissemination within the host. Such capsules are known as O-antigen (O-Ag) capsules, due to their high degree of similarity to the O-Ag of the lipopolysaccharide (LPSO-Ag). Group IV polysaccharide capsules are common in enteric bacteria and have more recently been described in nontyphoidalSalmonellaspecies. ![]()
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