title: Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human- mucus binding protein.
abstract: To unravel the biological function of the widely used probiotic bacterium Lactobacillus rhamnosus GG, we compared its 3.0-Mbp genome sequence with the similarly sized genome of L. rhamnosus LC705, an adjunct starter culture exhibiting reduced binding to mucus. Both genomes demonstrated high sequence identity and synteny. However, for both strains, genomic islands, 5 in GG and 4 in LC705, punctuated the colinearity. A significant number of strain-specific genes were predicted in these islands (80 in GG and 72 in LC705). The GG-specific islands included genes coding for bacteriophage components, sugar metabolism and transport, and exopolysaccharide biosynthesis. One island only found in L. rhamnosus GG contained genes for 3 secreted LPXTG-like pilins (spaCBA) and a pilin-dedicated sortase. Using anti-SpaC antibodies, the physical presence of cell wall-bound pili was confirmed by immunoblotting. Immunogold electron microscopy showed that the SpaC pilin is located at the pilus tip but also sporadically throughout the structure. Moreover, the adherence of strain GG to human intestinal mucus was blocked by SpaC antiserum and abolished in a mutant carrying an inactivated spaC gene. Similarly, binding to mucus was demonstrated for the purified SpaC protein. We conclude that the presence of SpaC is essential for the mucus interaction of L. rhamnosus GG and likely explains its ability to persist in the human intestinal tract longer than LC705 during an intervention trial. The presence of mucus-binding pili on the surface of a nonpathogenic Gram-positive bacterial strain reveals a previously undescribed mechanism for the interaction of selected probiotic lactobacilli with host tissues.
authors.affiliation: Institute of Biotechnology, University of Helsinki, P.O. Box 56, FIN-00014, Helsinki, Finland. matti.kankainen@helsinki.fi
authors.forename: Matti
authors.initials: M
authors.lastname: Kankainen
authors.forename: Lars
authors.initials: L
authors.lastname: Paulin
authors.forename: Soile
authors.initials: S
authors.lastname: Tynkkynen
authors.forename: Ingemar
authors.initials: I
authors.lastname: von Ossowski
authors.forename: Justus
authors.initials: J
authors.lastname: Reunanen
authors.forename: Pasi
authors.initials: P
authors.lastname: Partanen
authors.forename: Reetta
authors.initials: R
authors.lastname: Satokari
authors.forename: Satu
authors.initials: S
authors.lastname: Vesterlund
authors.forename: Antoni P A
authors.initials: AP
authors.lastname: Hendrickx
authors.forename: Sarah
authors.initials: S
authors.lastname: Lebeer
authors.forename: Sigrid C J
authors.initials: SC
authors.lastname: De Keersmaecker
authors.forename: Jos
authors.initials: J
authors.lastname: Vanderleyden
authors.forename: Tuula
authors.initials: T
authors.lastname: Hämäläinen
authors.forename: Suvi
authors.initials: S
authors.lastname: Laukkanen
authors.forename: Noora
authors.initials: N
authors.lastname: Salovuori
authors.forename: Jarmo
authors.initials: J
authors.lastname: Ritari
authors.forename: Edward
authors.initials: E
authors.lastname: Alatalo
authors.forename: Riitta
authors.initials: R
authors.lastname: Korpela
authors.forename: Tiina
authors.initials: T
authors.lastname: Mattila-Sandholm
authors.forename: Anna
authors.initials: A
authors.lastname: Lassig
authors.forename: Katja
authors.initials: K
authors.lastname: Hatakka
authors.forename: Katri T
authors.initials: KT
authors.lastname: Kinnunen
authors.forename: Heli
authors.initials: H
authors.lastname: Karjalainen
authors.forename: Maija
authors.initials: M
authors.lastname: Saxelin
authors.forename: Kati
authors.initials: K
authors.lastname: Laakso
authors.forename: Anu
authors.initials: A
authors.lastname: Surakka
authors.forename: Airi
authors.initials: A
authors.lastname: Palva
authors.forename: Tuomas
authors.initials: T
authors.lastname: Salusjärvi
authors.forename: Petri
authors.initials: P
authors.lastname: Auvinen
authors.forename: Willem M
authors.initials: WM
authors.lastname: de Vos
mesh_terms: D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D023281:Genomics / Q000379:methods*; D006801:Humans; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000378:metabolism / Q000648:ultrastructure; D052201:Lacticaseibacillus rhamnosus / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D008954:Models, Biological; D008969:Molecular Sequence Data; D009093:Mucus / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; C104625:SpaC protein, bacteria; D036781:Fimbriae Proteins