Assembly Pathways for Biosynthesis of A-Band and B-Band Lipopolysaccharide in Pseudomonas aeruginosa

Burrows, Lori L.; Rocchetta, Heather L.; Lam, Joseph S.

doi:10.1007/0-306-46821-2_5

Cited by 3 publications

(4 citation statements)

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“…These differences reflect the cellular location of assembly components for heteropolymeric and homopolymeric O antigens. This is briefly discussed below but is reviewed in detail by Burrows et al (28).…”

Section: Genes Encoding Glycosyltransferases For A-band Polymer Assemmentioning

confidence: 99%

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Genetics of O-Antigen Biosynthesis inPseudomonas aeruginosa

Rocchetta

Burrows

Lam

1999

Microbiol Mol Biol Rev

317

223

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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.

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Section: Genes Encoding Glycosyltransferases For A-band Polymer Assemmentioning

confidence: 99%

“…In 1996, sequencing of the entire O5 cluster was completed by our laboratory (28). More recently, the cloning and sequencing of the B-band O-antigen gene cluster from the clinically relevant IATS serotype O6 was completed by Bélanger et al (10).…”

Section: Genetics Of B-band O-antigen Biosynthesis Identification Andmentioning

confidence: 99%

Genetics of O-Antigen Biosynthesis inPseudomonas aeruginosa

Rocchetta

Burrows

Lam

1999

Microbiol Mol Biol Rev

317

223

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“…The O antigen protrudes into the environment and allows the bacterium to interact with its surroundings. There are 20 serotypes of P. aeruginosa (27), and 14 of those groups also produce the Aband saccharide known as common antigen, which is composed of D-rhamnose sugar polymer and consists of about 23 repeating units (6,47).LPS physical properties such as three-dimensional structure and number of repeating units contribute to bacterial adhesion (3,37,40). P. aeruginosa uses complicated biosynthetic mechanisms for assembly of LPS O antigen; this has been described extensively elsewhere (24).…”

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Relating the Physical Properties of Pseudomonas aeruginosa Lipopolysaccharides to Virulence by Atomic Force Microscopy

et al. 2011

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Lipopolysaccharides (LPS) are an important class of macromolecules that are components of the outer membrane of Gram-negative bacteria such as Pseudomonas aeruginosa. P. aeruginosa contains two different sugar chains, the homopolymer common antigen (A band) and the heteropolymer O antigen (B band), which impart serospecificity. The characteristics of LPS are generally assessed after isolation rather than in the context of whole bacteria. Here we used atomic force microscopy (AFM) to probe the physical properties of the LPS of P. aeruginosa strain PA103 (serogroup O11) in situ. This strain contains a mixture of long and very long polymers of O antigen, regulated by two different genes. For this analysis, we studied the wild-type strain and four mutants, ⌬Wzz1 (producing only very long LPS), ⌬Wzz2 (producing only long LPS), D⌬M (with both the wzz1 and wzz2 genes deleted), and Wzy::GM (producing an LPS core oligosaccharide plus one unit of O antigen). Forces of adhesion between the LPS on these strains and the silicon nitride AFM tip were measured, and the Alexander and de Gennes model of steric repulsion between a flat surface and a polymer brush was used to calculate the LPS layer thickness (which we refer to as length), compressibility, and spacing between the individual molecules. LPS chains were longest for the wild-type strain and ⌬Wzz1, at 170.6 and 212.4 nm, respectively, and these values were not statistically significantly different from one another. Wzy::GM and D⌬M have reduced LPS lengths, at 34.6 and 37.7 nm, respectively. Adhesion forces were not correlated with LPS length, but a relationship between adhesion force and bacterial pathogenicity was found in a mouse acute pneumonia model of infection. The adhesion forces with the AFM probe were lower for strains with LPS mutations, suggesting that the wild-type strain is optimized for maximal adhesion. Our research contributes to further understanding of the role of LPS in the adhesion and virulence of P. aeruginosa.Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that can cause several different types of infections in both community and health care settings and is especially problematic for immunocompromised and cystic fibrosis patients, as well as burn victims (23,32). Surface structures on the bacterium are related to virulence and the ability to cause infections. They make it possible for P. aeruginosa to attach to a wide range of surfaces, as well as to interact with components of the host (20). The lipopolysaccharide (LPS) is an important virulence factor for P. aeruginosa (25). The structure of LPS consists of lipid A, which anchors the LPS to the outer membrane, the core oligosaccharide, and the highly variable Oantigen side chain, which consists of repeating saccharide units and confers serotype specificity to the bacterium. The O antigen protrudes into the environment and allows the bacterium to interact with its surroundings. There are 20 serotypes of P. aeruginosa (27), and 14 of those groups also produce the Aband saccharide ...

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Regulation of Lipopolysaccharide O Antigen Expression in Pseudomonas Aeruginosa

Kintz

Goldberg

2008

Future Microbiol.

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Pseudomonas aeruginosa is a Gram-negative bacterium that is ubiquitously found in the environment. It is an important opportunistic pathogen in immunocompromised patients and causes life-threatening lung infections in individuals with cystic fibrosis. A prominent virulence factor for many Gram-negative bacteria, including P. aeruginosa, is lipopolysaccharide (LPS), which is an immunodominant antigen located in the outer portion of the outer membrane. P. aeruginosa produces two O antigens that are attached to lipid A + core: a B-band O antigen and an A-band O polysaccharide. The B-band O antigen-repeating unit of LPS is responsible for serotype specificity; strains lacking O antigen have been shown to be less virulent in animal models of infection. What is less well understood is how the O antigen chain length is regulated and why P. aeruginosa and some other bacteria show two preferred O antigen lengths. P. aeruginosa encodes two genes encoding O antigen chain length regulators. These genes, wzz1 and wzz2, influence the expression of the long and very long chain lengths, respectively. The long chain length appears more important for resistance to the action of sera and virulence in a mouse model of infection, while the very long chain length appears to be more sensitive to environmental stress conditions. Studies in other bacteria point to regulation at the level of transcription and complex formation as being involved in determining the O antigen chain length and may provide clues to the regulation in P. aeruginosa.

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Assembly Pathways for Biosynthesis of A-Band and B-Band Lipopolysaccharide in Pseudomonas aeruginosa

Cited by 3 publications

References 65 publications

Genetics of O-Antigen Biosynthesis inPseudomonas aeruginosa

Genetics of O-Antigen Biosynthesis inPseudomonas aeruginosa

Relating the Physical Properties of Pseudomonas aeruginosa Lipopolysaccharides to Virulence by Atomic Force Microscopy

Regulation of Lipopolysaccharide O Antigen Expression in Pseudomonas Aeruginosa

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