A second pilus type in Streptococcus pneumoniae is prevalent in emerging serotypes and mediates adhesion to host cells.
Analysis of publicly available genomes of Streptococcus pneumoniae has led to the identification of a new genomic element containing genes typical of gram-positive pilus islets (PIs). Here, we demonstrate that this genomic region, herein referred to as PI-2 (consisting of pitA, sipA, pitB, srtG1, and srtG2) codes for a second functional pilus in pneumococcus. Polymerization of the PI-2 pilus requires the backbone protein PitB as well as the sortase SrtG1 and the signal peptidase-like protein SipA. Presence of PI-2 correlates with the genotype as defined by multilocus sequence typing and clonal complex (CC). The PI-2-positive CCs are associated with serotypes 1, 2, 7F, 19A, and 19F, considered to be emerging serotypes in both industrialized and developing countries. Interestingly, strains belonging to CC271 (where sequence type 271 is the predicted founder of the CC) contain both PI-1 and PI-2, as revealed by genome analyses. In these strains both pili are surface exposed and independently assembled. Furthermore, in vitro experiments provide evidence that the pilus encoded by PI-2 of S. pneumoniae is involved in adherence. Thus, pneumococci encode at least two types of pili that play a role in the initial host cell contact to the respiratory tract and are potential antigens for inclusion in a new generation of pneumococcal vaccines.
Bagnoli
Fabio
F
Department of Cellular Microbiology and Bioinformatics, Novartis Vaccines, University of Siena, Siena 53100, Italy.
Moschioni
Monica
M
Donati
Claudio
C
Dimitrovska
Valentina
V
Ferlenghi
Ilaria
I
Facciotti
Claudia
C
Muzzi
Alessandro
A
Giusti
Fabiola
F
Emolo
Carla
C
Sinisi
Antonella
A
Hilleringmann
Markus
M
Pansegrau
Werner
W
Censini
Stefano
S
Rappuoli
Rino
R
Covacci
Antonello
A
Masignani
Vega
V
Barocchi
Michele A
MA
D001422:Bacterial Adhesion; D002460:Cell Line; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D023061:Gene Order; D005798:Genes, Bacterial; D044404:Genomic Islands; D005838:Genotype; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D011008:Pneumococcal Infections / Q000382:microbiology; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure
D004269:DNA, Bacterial