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.
Department of Cellular Microbiology and Bioinformatics, Novartis Vaccines, University of Siena, Siena 53100, Italy.
Fabio
F
Bagnoli
Monica
M
Moschioni
Claudio
C
Donati
Valentina
V
Dimitrovska
Ilaria
I
Ferlenghi
Claudia
C
Facciotti
Alessandro
A
Muzzi
Fabiola
F
Giusti
Carla
C
Emolo
Antonella
A
Sinisi
Markus
M
Hilleringmann
Werner
W
Pansegrau
Stefano
S
Censini
Rino
R
Rappuoli
Antonello
A
Covacci
Vega
V
Masignani
Michele A
MA
Barocchi
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