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Genetic and Functional Diversity of Pseudomonas aeruginosa Lipopolysaccharide.

Lam JS, Taylor VL, Islam ST, Hao Y, Kocíncová D - Front Microbiol (2011)

Bottom Line: Most P. aeruginosa strains produce two distinct forms of O-Ag, one a homopolymer of D-rhamnose that is a common polysaccharide antigen (CPA, formerly termed A band), and the other a heteropolymer of three to five distinct (and often unique dideoxy) sugars in its repeat units, known as O-specific antigen (OSA, formerly termed B band).Compositional differences in the O units among the OSA from different strains form the basis of the International Antigenic Typing Scheme for classification via serotyping of different strains of P. aeruginosa.The focus of this review is to provide state-of-the-art knowledge on the genetic and resultant functional diversity of LPS produced by P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, University of Guelph Guelph, ON, Canada.

ABSTRACT
Lipopolysccharide (LPS) is an integral component of the Pseudomonas aeruginosa cell envelope, occupying the outer leaflet of the outer membrane in this Gram-negative opportunistic pathogen. It is important for bacterium-host interactions and has been shown to be a major virulence factor for this organism. Structurally, P. aeruginosa LPS is composed of three domains, namely, lipid A, core oligosaccharide, and the distal O antigen (O-Ag). Most P. aeruginosa strains produce two distinct forms of O-Ag, one a homopolymer of D-rhamnose that is a common polysaccharide antigen (CPA, formerly termed A band), and the other a heteropolymer of three to five distinct (and often unique dideoxy) sugars in its repeat units, known as O-specific antigen (OSA, formerly termed B band). Compositional differences in the O units among the OSA from different strains form the basis of the International Antigenic Typing Scheme for classification via serotyping of different strains of P. aeruginosa. The focus of this review is to provide state-of-the-art knowledge on the genetic and resultant functional diversity of LPS produced by P. aeruginosa. The underlying factors contributing to this diversity will be thoroughly discussed and presented in the context of its contributions to host-pathogen interactions and the control/prevention of infection.

No MeSH data available.


Related in: MedlinePlus

Images from confocal laser scanning microscopy analyses of P. aeruginosa cells that illustrate the changes in biofilm structure resulting from truncation in the LPS core in mutant strains as comparing to the wildtype bacteria. Average projections (top panels) and midpoint cross sections (bottom panels) of representative microcolonies of (A) wildtype strain PAO1, (B) migA mutant, (C) wapR mutant, and (D) rmlC mutant are shown. Reproduced from Lau et al. (2009b), with permission from Copyright Clearance Centre.
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Figure 7: Images from confocal laser scanning microscopy analyses of P. aeruginosa cells that illustrate the changes in biofilm structure resulting from truncation in the LPS core in mutant strains as comparing to the wildtype bacteria. Average projections (top panels) and midpoint cross sections (bottom panels) of representative microcolonies of (A) wildtype strain PAO1, (B) migA mutant, (C) wapR mutant, and (D) rmlC mutant are shown. Reproduced from Lau et al. (2009b), with permission from Copyright Clearance Centre.

Mentions: Biofilm formation is the preferred mode of growth for P. aeruginosa cells clinging to rocks in fluvial streams or surviving in the lungs of CF patients in a chronic infection situation (Hall-Stoodley et al., 2004). Following planktonic growth of P. aeruginosa, attachment to a substratum is a prerequisite for establishing long-term colonization at a particular site to eventually adapt to a biofilm mode of growth. Biofilms are intricate surface-associated bacterial communities that confer survival advantages to the cells residing within and for which flagellar-mediated motility is important for their maturation in P. aeruginosa (O'toole and Kolter, 1998; Klausen et al., 2003). Consistent with the motility defects described above, the same mutants of P. aeruginosa lacking complete core OS and the distal CPA and OSA moieties were found to form biofilms with significant differences in mechanical and structural properties when compared to those of wildtype bacteria. This evidence was collected from a variety of quantitative measurement studies to determine changes in ultrastructures, biophysical properties, cell–cell adhesion forces, and viscoelasticity of mutant and wildtype strains using a technique called microbead force spectroscopy (Lau et al., 2009a). Several bacterial strains including knockout mutants disrupted in migA, wapR, and rmlC, respectively, and with defined core OS truncation characteristics were compared to their wildtype PAO1 parent strain in these studies. Significant changes were observed in cell mechanical properties among the mutant strains compared to the wildtype PAO1. The functions of migA and wapR have been described earlier; the rmlC gene is responsible for TDP-L-Rha biosynthesis and hence a rmlC mutant produces a defective core OS truncated at the RhaA and RhaB residues in the two glycoforms of the core OS (Figure 4). The data from these studies revealed that truncation of core OS enhanced both adhesive and cohesive forces by up to 10-fold, whereas changes in instantaneous elasticity were correlated with the presence of O-Ag. Using AFM to raster-scan bacterial cells in air in contact mode for each of the aforementioned four strains showed differences in the texture of the surface “smoothness.” Interestingly, LPS-“smooth” strain wildtype PAO1 with O-Ag exhibits rougher surface topography than rough strains, i.e., the mutant bacterial strains of migA, wapR, and rmlC (Figure 6). Using confocal laser scanning microscopy to quantify biofilm structural changes in these mutants, we observed that textural parameters varied with adhesion or the inverse of cohesion, while areal and volumetric parameters were linked to adhesion, cohesion, or the balance between them. Microcolonies formed by cells of the wildtype PAO1 had round perimeters, while the microcolonies formed by the mutant strains had more irregular edges (Figure 7; Lau et al., 2009b). These studies support the importance of O-Ag in the formation of cellular structures and the physiology of P. aerugionsa in a biofilm mode of growth. In a study by Ivanov et al. (2011), they showed that changes in the relative proportion of OSA modalities as well as the outright loss of OSA result in reduced virulence of P. aeruginosa consistent with diminished surface adhesive forces, further supporting the role of LPS-mediated adhesion in P. aeruginosa persistence. The observations made in these recent studies substantiated an earlier report in which rough mutants of P. aeruginosa lacking OSA had an LD50 that was 1000X higher than that of a wildtype strain in a mouse infection model (Cryz et al., 1984).


Genetic and Functional Diversity of Pseudomonas aeruginosa Lipopolysaccharide.

Lam JS, Taylor VL, Islam ST, Hao Y, Kocíncová D - Front Microbiol (2011)

Images from confocal laser scanning microscopy analyses of P. aeruginosa cells that illustrate the changes in biofilm structure resulting from truncation in the LPS core in mutant strains as comparing to the wildtype bacteria. Average projections (top panels) and midpoint cross sections (bottom panels) of representative microcolonies of (A) wildtype strain PAO1, (B) migA mutant, (C) wapR mutant, and (D) rmlC mutant are shown. Reproduced from Lau et al. (2009b), with permission from Copyright Clearance Centre.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108286&req=5

Figure 7: Images from confocal laser scanning microscopy analyses of P. aeruginosa cells that illustrate the changes in biofilm structure resulting from truncation in the LPS core in mutant strains as comparing to the wildtype bacteria. Average projections (top panels) and midpoint cross sections (bottom panels) of representative microcolonies of (A) wildtype strain PAO1, (B) migA mutant, (C) wapR mutant, and (D) rmlC mutant are shown. Reproduced from Lau et al. (2009b), with permission from Copyright Clearance Centre.
Mentions: Biofilm formation is the preferred mode of growth for P. aeruginosa cells clinging to rocks in fluvial streams or surviving in the lungs of CF patients in a chronic infection situation (Hall-Stoodley et al., 2004). Following planktonic growth of P. aeruginosa, attachment to a substratum is a prerequisite for establishing long-term colonization at a particular site to eventually adapt to a biofilm mode of growth. Biofilms are intricate surface-associated bacterial communities that confer survival advantages to the cells residing within and for which flagellar-mediated motility is important for their maturation in P. aeruginosa (O'toole and Kolter, 1998; Klausen et al., 2003). Consistent with the motility defects described above, the same mutants of P. aeruginosa lacking complete core OS and the distal CPA and OSA moieties were found to form biofilms with significant differences in mechanical and structural properties when compared to those of wildtype bacteria. This evidence was collected from a variety of quantitative measurement studies to determine changes in ultrastructures, biophysical properties, cell–cell adhesion forces, and viscoelasticity of mutant and wildtype strains using a technique called microbead force spectroscopy (Lau et al., 2009a). Several bacterial strains including knockout mutants disrupted in migA, wapR, and rmlC, respectively, and with defined core OS truncation characteristics were compared to their wildtype PAO1 parent strain in these studies. Significant changes were observed in cell mechanical properties among the mutant strains compared to the wildtype PAO1. The functions of migA and wapR have been described earlier; the rmlC gene is responsible for TDP-L-Rha biosynthesis and hence a rmlC mutant produces a defective core OS truncated at the RhaA and RhaB residues in the two glycoforms of the core OS (Figure 4). The data from these studies revealed that truncation of core OS enhanced both adhesive and cohesive forces by up to 10-fold, whereas changes in instantaneous elasticity were correlated with the presence of O-Ag. Using AFM to raster-scan bacterial cells in air in contact mode for each of the aforementioned four strains showed differences in the texture of the surface “smoothness.” Interestingly, LPS-“smooth” strain wildtype PAO1 with O-Ag exhibits rougher surface topography than rough strains, i.e., the mutant bacterial strains of migA, wapR, and rmlC (Figure 6). Using confocal laser scanning microscopy to quantify biofilm structural changes in these mutants, we observed that textural parameters varied with adhesion or the inverse of cohesion, while areal and volumetric parameters were linked to adhesion, cohesion, or the balance between them. Microcolonies formed by cells of the wildtype PAO1 had round perimeters, while the microcolonies formed by the mutant strains had more irregular edges (Figure 7; Lau et al., 2009b). These studies support the importance of O-Ag in the formation of cellular structures and the physiology of P. aerugionsa in a biofilm mode of growth. In a study by Ivanov et al. (2011), they showed that changes in the relative proportion of OSA modalities as well as the outright loss of OSA result in reduced virulence of P. aeruginosa consistent with diminished surface adhesive forces, further supporting the role of LPS-mediated adhesion in P. aeruginosa persistence. The observations made in these recent studies substantiated an earlier report in which rough mutants of P. aeruginosa lacking OSA had an LD50 that was 1000X higher than that of a wildtype strain in a mouse infection model (Cryz et al., 1984).

Bottom Line: Most P. aeruginosa strains produce two distinct forms of O-Ag, one a homopolymer of D-rhamnose that is a common polysaccharide antigen (CPA, formerly termed A band), and the other a heteropolymer of three to five distinct (and often unique dideoxy) sugars in its repeat units, known as O-specific antigen (OSA, formerly termed B band).Compositional differences in the O units among the OSA from different strains form the basis of the International Antigenic Typing Scheme for classification via serotyping of different strains of P. aeruginosa.The focus of this review is to provide state-of-the-art knowledge on the genetic and resultant functional diversity of LPS produced by P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, University of Guelph Guelph, ON, Canada.

ABSTRACT
Lipopolysccharide (LPS) is an integral component of the Pseudomonas aeruginosa cell envelope, occupying the outer leaflet of the outer membrane in this Gram-negative opportunistic pathogen. It is important for bacterium-host interactions and has been shown to be a major virulence factor for this organism. Structurally, P. aeruginosa LPS is composed of three domains, namely, lipid A, core oligosaccharide, and the distal O antigen (O-Ag). Most P. aeruginosa strains produce two distinct forms of O-Ag, one a homopolymer of D-rhamnose that is a common polysaccharide antigen (CPA, formerly termed A band), and the other a heteropolymer of three to five distinct (and often unique dideoxy) sugars in its repeat units, known as O-specific antigen (OSA, formerly termed B band). Compositional differences in the O units among the OSA from different strains form the basis of the International Antigenic Typing Scheme for classification via serotyping of different strains of P. aeruginosa. The focus of this review is to provide state-of-the-art knowledge on the genetic and resultant functional diversity of LPS produced by P. aeruginosa. The underlying factors contributing to this diversity will be thoroughly discussed and presented in the context of its contributions to host-pathogen interactions and the control/prevention of infection.

No MeSH data available.


Related in: MedlinePlus