Limits...
RrgA is a pilus-associated adhesin in Streptococcus pneumoniae.

Nelson AL, Ries J, Bagnoli F, Dahlberg S, Fälker S, Rounioja S, Tschöp J, Morfeldt E, Ferlenghi I, Hilleringmann M, Holden DW, Rappuoli R, Normark S, Barocchi MA, Henriques-Normark B - Mol. Microbiol. (2007)

Bottom Line: Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself.In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy.These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

View Article: PubMed Central - PubMed

Affiliation: Swedish Institute for Infectious Disease Control and Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Adherence to host cells is important in microbial colonization of a mucosal surface, and Streptococcus pneumoniae adherence was significantly enhanced by expression of an extracellular pilus composed of three subunits, RrgA, RrgB and RrgC. We sought to determine which subunit(s) confers adherence. Bacteria deficient in RrgA are significantly less adherent than wild-type organisms, while overexpression of RrgA enhances adherence. Recombinant monomeric RrgA binds to respiratory cells, as does RrgC with less affinity, and pre-incubation of epithelial cells with RrgA reduces adherence of wild-type piliated pneumococci. Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself. In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy. The density of bacteria colonizing the upper respiratory tract of mice inoculated with piliated RrgA-negative pneumococci was significantly less compared with wild-type; in contrast, non-piliated pneumococci expressing non-polymeric RrgA had similar numbers of bacteria in the nasopharynx as piliated wild-type bacteria. These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

Show MeSH

Related in: MedlinePlus

RrgA is involved in pilus-mediated colonization of the upper respiratory tract in mice. Mice were challenged intranasally with a low dose of T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). Bacterial density in the nasopharynx was determined 7 days post infection. Mice infected with T4ΔrrgA had significantly fewer bacteria in the nasopharynx than mice infected with T4 or T4ΔrrgBC (*P< 0.01, n = 3 independent replicates of 10 mice per group per replicate, using the Kruskal–Wallis test with Dunn's post testing).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2170534&req=5

fig05: RrgA is involved in pilus-mediated colonization of the upper respiratory tract in mice. Mice were challenged intranasally with a low dose of T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). Bacterial density in the nasopharynx was determined 7 days post infection. Mice infected with T4ΔrrgA had significantly fewer bacteria in the nasopharynx than mice infected with T4 or T4ΔrrgBC (*P< 0.01, n = 3 independent replicates of 10 mice per group per replicate, using the Kruskal–Wallis test with Dunn's post testing).

Mentions: In addition to adherence to host epithelium, failure to express RrgA in a mouse model of pneumonia significantly impairs bacterial competition (Hava and Camilli, 2002), supporting an important role for this gene product in vivo in the respiratory tract. It has also been reported that the pneumococcal pilus confers a more pathogenic phenotype in a mouse model of intraperitoneal sepsis (Barocchi et al., 2006), although no specific role for any single subunit has been demonstrated. Given the importance of RrgA in adherence in vitro, we tested the contribution of RrgA in a mouse model of colonization of the upper airways. Mice were challenged with a low dose of piliated T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). The bacterial density in the nasopharynx of mice infected with the strain lacking only RrgA was significantly lower compared with wild-type T4 1 week post infection (P< 0.01) (Fig. 5). Mice infected with the strain lacking both RrgB and RrgC, and therefore the pilus polymer, did not exhibit any significant difference in upper respiratory bacterial density when compared with wild-type bacteria. These data support a critical role for RrgA in pilus-mediated colonization in a host animal.


RrgA is a pilus-associated adhesin in Streptococcus pneumoniae.

Nelson AL, Ries J, Bagnoli F, Dahlberg S, Fälker S, Rounioja S, Tschöp J, Morfeldt E, Ferlenghi I, Hilleringmann M, Holden DW, Rappuoli R, Normark S, Barocchi MA, Henriques-Normark B - Mol. Microbiol. (2007)

RrgA is involved in pilus-mediated colonization of the upper respiratory tract in mice. Mice were challenged intranasally with a low dose of T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). Bacterial density in the nasopharynx was determined 7 days post infection. Mice infected with T4ΔrrgA had significantly fewer bacteria in the nasopharynx than mice infected with T4 or T4ΔrrgBC (*P< 0.01, n = 3 independent replicates of 10 mice per group per replicate, using the Kruskal–Wallis test with Dunn's post testing).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2170534&req=5

fig05: RrgA is involved in pilus-mediated colonization of the upper respiratory tract in mice. Mice were challenged intranasally with a low dose of T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). Bacterial density in the nasopharynx was determined 7 days post infection. Mice infected with T4ΔrrgA had significantly fewer bacteria in the nasopharynx than mice infected with T4 or T4ΔrrgBC (*P< 0.01, n = 3 independent replicates of 10 mice per group per replicate, using the Kruskal–Wallis test with Dunn's post testing).
Mentions: In addition to adherence to host epithelium, failure to express RrgA in a mouse model of pneumonia significantly impairs bacterial competition (Hava and Camilli, 2002), supporting an important role for this gene product in vivo in the respiratory tract. It has also been reported that the pneumococcal pilus confers a more pathogenic phenotype in a mouse model of intraperitoneal sepsis (Barocchi et al., 2006), although no specific role for any single subunit has been demonstrated. Given the importance of RrgA in adherence in vitro, we tested the contribution of RrgA in a mouse model of colonization of the upper airways. Mice were challenged with a low dose of piliated T4, T4ΔrrgA or T4ΔrrgBC (c. 7 × 104 cfu per mouse). The bacterial density in the nasopharynx of mice infected with the strain lacking only RrgA was significantly lower compared with wild-type T4 1 week post infection (P< 0.01) (Fig. 5). Mice infected with the strain lacking both RrgB and RrgC, and therefore the pilus polymer, did not exhibit any significant difference in upper respiratory bacterial density when compared with wild-type bacteria. These data support a critical role for RrgA in pilus-mediated colonization in a host animal.

Bottom Line: Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself.In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy.These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

View Article: PubMed Central - PubMed

Affiliation: Swedish Institute for Infectious Disease Control and Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Adherence to host cells is important in microbial colonization of a mucosal surface, and Streptococcus pneumoniae adherence was significantly enhanced by expression of an extracellular pilus composed of three subunits, RrgA, RrgB and RrgC. We sought to determine which subunit(s) confers adherence. Bacteria deficient in RrgA are significantly less adherent than wild-type organisms, while overexpression of RrgA enhances adherence. Recombinant monomeric RrgA binds to respiratory cells, as does RrgC with less affinity, and pre-incubation of epithelial cells with RrgA reduces adherence of wild-type piliated pneumococci. Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself. In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy. The density of bacteria colonizing the upper respiratory tract of mice inoculated with piliated RrgA-negative pneumococci was significantly less compared with wild-type; in contrast, non-piliated pneumococci expressing non-polymeric RrgA had similar numbers of bacteria in the nasopharynx as piliated wild-type bacteria. These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

Show MeSH
Related in: MedlinePlus