Genetic Analysis of the Capsular Biosynthetic Locus from All 90 Pneumococcal Serotypes

Abstract

Several major invasive bacterial pathogens are encapsulated. Expression of a polysaccharide capsule is essential for survival in the blood, and thus for virulence, but also is a target for host antibodies and the basis for effective vaccines. Encapsulated species typically exhibit antigenic variation and express one of a number of immunochemically distinct capsular polysaccharides that define serotypes. We provide the sequences of the capsular biosynthetic genes of all 90 serotypes of Streptococcus pneumoniae and relate these to the known polysaccharide structures and patterns of immunological reactivity of typing sera, thereby providing the most complete understanding of the genetics and origins of bacterial polysaccharide diversity, laying the foundations for molecular serotyping. This is the first time, to our knowledge, that a complete repertoire of capsular biosynthetic genes has been available, enabling a holistic analysis of a bacterial polysaccharide biosynthesis system. Remarkably, the total size of alternative coding DNA at this one locus exceeds 1.8 Mbp, almost equivalent to the entire S. pneumoniae chromosomal complement.

WciG O -Acetyltransferase Functionality Differentiates Pneumococcal Serotypes 35C and 42

“…The chemical structures suggest that WcjE acetylates the 5-and 6-positions of 3-␤-Galf in the polysaccharides of both serotypes. This is consistent with other reports of O-acetylation in serotypes 20, 31, 33A, 35A, and 47A (2), which also carry wcjE (11,16). Thus, WciG acetylates the 2-position of the 6-␤-Galf in the serotype 35C repeat unit, and 2-OAc␤Galf ("OAc" represents O-acetylation) is essential for factor serum 35a recognition.…”

“…They are the targets of many serotyping reagents, innate immune molecules (e.g., ficolin-2 [14,18] and siglecs [19]), and vaccine-elicited antibodies (20). Pneumococcal cps loci harbor many acetyltransferase genes (11), and several serogroups contain serotype pairs: one with a functional transferase and the other with nonfunctional transferase. For example, WcjE-positive and -negative pairs have been observed in serogroups 9, 11, and 33 (11,21).…”

“…Despite distinct immunological profiles, their reference cps loci are nearly identical (see Table S1 in the supplemental material) and contain the same genes in the same arrangement, with two intact O-acetyltransferase genes (wcjE and wciG [see Fig. 2A]) (11). However, biochemical studies showed that serotype 42 capsular polysaccharide (CPS) has two O-acetylations on its 3-linked ␤-galactofuranose (Galf) (12,13), while a commercial serotype 35C capsule preparation contained no O-acetylation (13).…”

Lectin Microarray Reveals Binding Profiles of Lactobacillus casei Strains in a Comprehensive Analysis of Bacterial Cell Wall Polysaccharides

“…In addition, it has been shown that extracellular PSs of Streptococcus thermophilus (39) and group B Streptococcus capsular PSs are highly diverse (6). It is well-known that pathogenic bacteria, such as hemolytic streptococci, often change their outer surface glycan profile to escape the host immune defense mechanism (5). To investigate the dynamism and diversity of bacterial outer surface structures, especially bacterial glycomes, in relation to their functional characterization, a powerful methodology with high throughput and versatility is needed.…”

Sequence-structure relationships in polysaccharide co-polymerase (PCP) proteins

“…The biosynthesis of many lipopolysaccharide (LPS) O-antigens (Oags), enterobacterial common antigen (ECA) and some capsule polysaccharides (CPSs) in Gram-negative and Gram-positive bacteria occurs by a mechanism known as the Wzy polymerasedependent pathway [1][2][3][4]. The process relies on a putative, multifunctional protein complex involving homologues of the inner membrane proteins Wzx, Wzy and Wzz [5].…”