Role Of Pili Research Articles

Role of pili in the adherence of Pseudomonas aeruginosa to injured tracheal epithelium.

Pili have been demonstrated to be the adhesins of nonmucoid Pseudomonas aeruginosa for buccal cells. In this study, we examined their role in the adherence of both mucoid and nonmucoid strains to injured tracheal cells. Pili incubated with tracheal cells inhibited the adherence of a nonmucoid strain in a dose-dependent manner. Both homologous and heterologous pili inhibited this nonmucoid strain. Antibody against pili from the nonmucoid strain inhibited adherence of the homologous but not a heterologous strain. Pili failed to inhibit two mucoid strains, but inhibited nonmucoid variants derived from mucoid strains. These studies suggest that pili mediate the adherence of nonmucoid strains to injured tracheal cells but that they are not the final mediators of adherence of mucoid strains. It is also inferred that there are differences in the receptor for mucoid and nonmucoid strains.

The role of pili and capsule in the pathogenesis of neonatal infection with Escherichia coli K1.

The role of pili and capsule was studied in neonatal infection with Escherichia coli K1. E coli strains were selectively cultured into three phases: mannose-sensitive (MS) piliated, non-mannose-sensitive (NMS) piliated, and nonpiliated. A high percentage of neonatal rats fed each phase of K1 strains developed bacteremia; there was no bacteremia with non-K1 strains or an acapsular mutant of K1 strain C94 (C94K-). Oral cavity colonization was noted in nearly 100% of rats fed K1 strains, non-K1 strains, or C94K-, regardless of the phase of piliation at feeding. Only MS piliated bacteria were found on oral cavity culture, indicating a rapid shift of NMS piliated and nonpiliated bacteria to the MS piliated phase. Conversely, only nonpiliated bacteria were found on blood culture when neonatal rats were fed piliated bacteria. Colonization of ileal epithelium was not observed. Thus, in vivo phase variation may be important in colonization and bacteremia with E coli K1.

Transmission electron microscope studies of a piliated strain of Haemophilus influenzae B

The role of pili as a mucosal attachment factor that enhances colonization and pathogenicity is well known in Escherichia coli, Neisseria gonorrhea, Streptococcus pyrogenes and Proteus mirabilis. Although Haemophilus influenzae type b (Hib) causes serious infections in children such as meningitis, pneumonia, septic arthritis and epiglottitis, very little information is available about Hib piliation and subsequent adhesion and colonization in vivo. Hib piliation was recently correlated with hemagglutination and adherence (in vitro) to human buccal epithelial cells by Pichichero, et al.Pili are protein structures which extend from the outer membrane of Hib. Purified pili have an apparent molecular weight of 23,000 daltons by Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and aggregate laterally as well as end on end to form thick filamentous structures. Although pili seem to enhance attachment to respiratory mucosa (a significant foothold during the invasion of healthy tissue) the relative pathogenicity of piliated and non-piliated Hib is yet to be determined.

The role of pili and outer membrane vesicles in the immunogenicity of Neisseria gonorrhoeae in the guinea pig chamber model

The role of pili and outer membrane vesicles in the immunogenicity of Neisseria gonorrhoeae in the guinea pig chamber model

Lack of significance of pili in experimental ascending Escherichia coli pyelonephritis.

The role of pili as a bacterial virulence factor has been studied. The model used was acute ascending Escherichia coli pyelonephritis in the mouse. Three strains of E. coli were injected in lightly or more heavily piliated phases into 15 mice each. At sacrifice of 13-15 animals 2 weeks later, no significant difference in severity of pyelonephritis was found as judged by numbers of bacteria in the kidney, nor intensity or frequency of gross abscesses. 27 strains of E. coli were order ranked for severity of pyelonephritis produced and compared with intensity of piliation in vitro under conditions designed to maximize pilus formation. No significant difference was found. 15 strains derived from patients in whom infections were confined to the bladder were compared for degree of piliation with 12 strains infecting the kidney. No significant difference was found. These studies do not support a significant role for the degree of piliation as a virulence factor in pyelonephritis.

Adherence properties of Pseudomonas pili to epithelial cells of the human cornea.

In vitro adherence of Pseudomonas fluorescens organisms to the human cornea is correlated with bacterial pili. The role of pili in the attachment to human corneal epithelial cells was studied in an in vitro adherence assay system. A homogeneous, purified pilin preparation showed a molecular weight of 16,500 on SDS-polyacrylamide gels. Within 5 minutes incubation, 5.5 pg of pilin adhere to 15,000 epithelial cells. When epithelial cells were preincubated with purified pilin, a subsequent decrease in adherence of labeled pilin was noted. It appears that pili mediate adherence of Pseudomonas organism to human cornea.

Hemagglutination reaction and epithelial cell adherence activity of Serratia marcescens.

Although Serratia marcescens has been reported to possess pili, little attention has been given to the role of the pill in this organism. This piliated bacterium agglutinates human and chicken erythrocytes, and the activity is inhibited by α-D-mannose. The degree of piliation, induced by shaking or static culture conditions, correlate with the hemagglutination activity. S. marcescens depiliated by UV irradiation failed to agglutinate erythrocytes. The possible role of pili as an important virulence factor in promoting adherence to host cells was studied by investigating the ability of piliated S. marcescens to attach to buccal epithelial cells. Results showed that S. marcescens attached to human buccal epithelial cells and that adherence is associated with the presence of common type-1 pili on their surfaces.

Effect of piliation on Klebsiella pneumoniae infection in rat bladders.

The possible role of pili in the pathogenesis of urinary tract infection caused by Klebsiella pneumoniae was investigated in a rat model of cystitis by utilizing piliated- and nonpiliated-phase organisms derived from a single parent strain. Bladder surfaces were examined for evidence of infection by scanning electron microscopy. In animals infected with piliated-phase organisms, foci of infection were evident in the majority of bladders examined. Rat bladders associated with nonpiliated-phase bacteria showed little evidence of infection. The ability of methyl-D-mannoside, a known inhibitor of pilus-mediated adherence to mammalian cells, to protect the bladder surface from colonization was also tested. The results showed a significant decrease in the ability of piliated-phase K. pneumoniae to establish infection in bladders. These observations suggest that pili may play an integral role in the ability of K. pneumoniae to cause urinary tract infections by mediating the attachment of the bacteria to the uroepithelial surface.

Role of pili in adherence of Pseudomonas aeruginosa to mammalian buccal epithelial cells.

Adherence of Pseudomonas aeruginosa organisms to the upper respiratory epithelium of seriously ill patients in vitro is correlated with subsequent colonization of the respiratory tract by this opportunistic pathogen. The role of pili in the attachment to epithelial cells of P. aeruginosa was studied in an in vitro system employing human buccal epithelial cells and P. aeruginosa pretreated by various means. Pretreatment of the bacteria with proteases, heat, or Formalin caused a significant decrease in adherence. A decrease when compared with controls was also noted in the adherence of P. aeruginosa organisms to buccal epithelial cells preincubated with purified pili prepared from the strain used for adherence testing; however, pili prepared from a heterologous strain failed to block adherence. Similar results were obtained in serological studies when antisera to purified pili prepared from the strain used for adherence testing decreased adherence, whereas heterologous antiserum to pili did not decrease adherence. From these results it appears that pili mediate the adherence of P. aeruginosa organisms to human buccal epithelial cells.

Evidence for pili-mediated adherence of Klebsiella pneumoniae to rat bladder epithelial cells in vitro.

The possible role of pili in the pathogenesis of urinary tract infections caused by Klebsiella pneumoniae was studied in an in vitro mixture of a phosphate-buffered saline suspension of rat bladder epithelial cells and phosphate-buffered saline-washed K. pneumoniae. Nonpiliated and piliated populations derived from a single K. pneumoniae strain were obtained by controlling the total time of growth in broth medium. The piliated phase demonstrated a significant increase in adherence when compared to the nonpiliated phase. Incubation of the bacteria and epithelial cell mixture at 4 and 37 degrees C resulted in no differences in adherence; optimal adherence occurred at pH 5. Pretreatment of the bacteria with enzymes to destroy the pili resulted in a decrease in adherence, as did killing the bacteria by various means before adherence testing. Pretreatment of the epithelial cells with certain saccharides inhibited bacterial adherence. Finally, a 96% decrease in adherence was observed after coincubation of bacteria and epithelial cells with papain-treated antipili antibodies. Thus, it appears that pili on the surface of K. pneumoniae mediate attachment of the bacteria to rat bladder epithelial cells.

Role of pili in the virulence of Neisseria gonorrhoeae.

Gonococci of the colonial types that are associated with virulence, types 1 and 2, have pili that enable the bacteria both to attach in vitro to human epithelial cells and to resist phagocytosis by polymorphonuclear leukocytes. These piliated gonococci also agglutinate various mammalian and chicken erythrocytes. Gonococci of an avirulent colonial type, i.e., type 4, have no pili and neither attach to epithelial cells or erythrocytes nor resist phagocytosis. Like the type 4 bacteria, mechanically or enzymatically (trypsin) depiliated type 1 gonococci failed to attach to epithelial cells and erythrocytes and were susceptible to phagocytosis. Pili of types 1 and 2 gonococci were antigenically similar. Both type 1 gonococci and pili isolated from them induced in rabbits antibody that (i) precipitated gonococcal pili in immunodiffusion, (ii) reacted with piliated gonococci as tested by indirect immunofluorescent analysis, (iii) inhibited attachment of piliated gonococci to both human epithelial cells and erythrocytes, and (iv) opsonized piliated gonococci.

Repair of wall damage in Escherichia coli recovered from an aerosol.

Supramembrane structures that connect conjugating agrobacterial cells were visualized for the first time by transmission electron microscopy. The primary contact of cells during conjugation was shown to occur through the formation of long pili containing no VirB1 protein. Pretreatment of agrobacterial cells with acetosyringone resulted in a six- to tenfold increase in the transfer frequency of the plasmid pTd33 at 19-25 degrees C and had almost no effect at 30 degrees C. The transfer of the plasmid pTd33 from A. tumefaciens strain GV3101 to plasmid-free A. tumefaciens strain UBAPF-2 was 16 times decreased after the centrifugation of cells. The transfer efficiency of the plasmid pTd33 from A. tumefaciens strain LBA2525 (virB2::lacZ) to plasmid-free A. tumefaciens strain UBAPF-2 was one order of magnitude lower than the transfer from the wild-type A. tumefaciens strain GV3101. Treatment of donor cells with 0.01% SDS before mating decreased the transfer efficiency by a factor of 26. The role of pili in the establishment of contact between conjugating cells of agrobacteria is discussed.

Role of pili in bacterial conjugation.

We describe techniques for isolating individual pairs of mating Escherichia coli and observing them under the light microscope. Some pairs achieved close cell-to-cell contact, whereas others remained loosely connected by invisible connections which may be F pili. After 30 min of mating, the pairs were separated and allowed to grow into clones. That many exconjugants derived from "loose"-mating pairs produced recombinants suggests that F pili are involved in the transfer of genetic material. The frequency of formation of recombinants from "close"-mating pairs, however, was significantly higher than that from loose-mating pairs, indicating that a close cell-to-cell contact facilitates chromosome transfer. Death rates of exconjugants from close pairs were also higher than those from loose pairs. Hfr x F(-) matings produced higher death rates than F(+) x F(-) matings. Male cells were found capable of transferring genetic markers to two F(-) cells simultaneously. We conclude that F pili play at least three roles in mating: (i) they initiate contacts between mating pairs; (ii) they facilitate the transfer of genetic material; and (iii) they draw mating cells into a close contact which increases the fertility of the union.