Genetics of O-Antigen Biosynthesis inPseudomonas aeruginosa

Abstract

SUMMARY Pathogenic bacteria produce an elaborate assortment of extracellular and cell-associated bacterial products that enable colonization and establishment of infection within a host. Lipopolysaccharide (LPS) molecules are cell surface factors that are typically known for their protective role against serum-mediated lysis and their endotoxic properties. The most heterogeneous portion of LPS is the O antigen or O polysaccharide, and it is this region which confers serum resistance to the organism. Pseudomonas aeruginosa is capable of concomitantly synthesizing two types of LPS referred to as A band and B band. The A-band LPS contains a conserved O polysaccharide region composed of d-rhamnose (homopolymer), while the B-band O-antigen (heteropolymer) structure varies among the 20 O serotypes of P. aeruginosa. The genes coding for the enzymes that direct the synthesis of these two O antigens are organized into two separate clusters situated at different chromosomal locations. In this review, we summarize the organization of these two gene clusters to discuss how A-band and B-band O antigens are synthesized and assembled by dedicated enzymes. Examples of unique proteins required for both A-band and B-band O-antigen synthesis and for the synthesis of both LPS and alginate are discussed. The recent identification of additional genes within the P. aeruginosa genome that are homologous to those in the A-band and B-band gene clusters are intriguing since some are able to influence O-antigen synthesis. These studies demonstrate that P. aeruginosa represents a unique model system, allowing studies of heteropolymeric and homopolymeric O-antigen synthesis, as well as permitting an examination of the interrelationship of the synthesis of LPS molecules and other virulence determinants.

Synthesis of multiple Pseudomonas aeruginosa biofilm matrix exopolysaccharides is post‐transcriptionally regulated

“…In addition, the lack of Psl in the algC mutant was not due to the LPS defect. Taken together, our data revealed that AlgC was required for the biosynthesis of Psl, likely due to the role of AlgC in generating the precursors as it does in the biosynthesis pathway of alginate and LPS (Coyne et al, 1994;Deretic et al, 1995;Rocchetta et al, 1999).…”

“…The control of the surface polysaccharide synthesis is a critical bacterial survival in the environment and human host (Rocchetta et al, 1999;Hall-Stoodley et al, 2004;Ramsey and Wozniak, 2005;Danhorn and Fuqua, 2007;Hoiby et al, 2010). Pseudomonas aeruginosa can produce several exopolysaccharides; each has distinct roles in biofilm development (Ghafoor et al, 2011;Yang et al, 2011).…”

Structural characterization of the outer core and the O‐chain linkage region of lipopolysaccharide from Pseudomonas aeruginosa serotype O5

“…The genetics of the O-chain biosynthesis in P. aeruginosa has been extensively characterized and reviewed by Rocchetta et al [32]. The genes encoding the glycosyl transferases for the transfer of the sugar residues of the O-antigen units of serotype O5 and O6 have been identified.…”

Structural analysis of the lipopolysaccharide core of a rough, cystic fibrosis isolate of Pseudomonas aeruginosa

“…Although significant progress has been made in identifying genes involved in LPS synthesis in P. aeruginosa [8][9][10][11][12], the genetic changes leading to stable acquisition of the LPS rough phenotype have not yet been correlated with the chemical changes that occur in the LPS of cystic fibrosis isolates. Core structures for P. aeruginosa serogroups O2, O3, O5 and O6 and derived mutant strains have been reported [13][14][15][16][17][18][19][20].…”