The oligopeptide (opp) gene cluster of Streptococcus mutans: identification, prevalence, and characterization.
BACKGROUND
The Opp system is an ATP-binding cassette-type transporter formed by membrane-associated proteins required for the uptake of oligopeptides in bacteria. In gram-positive bacteria, the Opp system, and particularly the oligopeptide-binding protein (OppA), has been shown to be involved in different aspects of cell physiology, including intercellular communication and binding to host proteins.


METHODS
In the present study we began to investigate the Opp system of Streptococcus mutans, the main etiological agent of dental caries.


RESULTS
Five opp genes (oppABCDF) organized in a single operon were identified in the genome of the S. mutans UA159 strain. Amino acid sequence analyses showed that the S. mutans OppA is closely related to an ortholog found in Streptococcus agalactiae. Incubation of S. mutans UA159 cells with an anti-OppA-specific serum did not inhibit biofilm formation on polystyrene plates. Moreover, S. mutans UA159 derivatives carrying deletions on the oppA or oppB genes did not show significant growth impairment, increased sensitivity to aminopterin, or defective capacity to form biofilms on polystyrene wells in the presence or not of saliva. Remarkably, only two out of three laboratory strains and one out of seven clinical strains recovered from tooth decay processes harbored a copy of the oppA gene and expressed the OppA protein.


CONCLUSIONS
Collectively, these results indicate that, in contrast to other Streptococcus species, the S. mutans Opp system, and particularly the OppA protein, does not represent an important trait required for growth and colonization.
Nepomuceno
R S L
RS
Department of Microbiology, Biomedical Sciences Institute, University of São Paulo, Cidade Universitária, SP, Brazil.
Tavares
M B
MB
Lemos
J A
JA
Griswold
A R
AR
Ribeiro
J L
JL
Balan
A
A
Guimarães
K S
KS
Cai
S
S
Burne
R A
RA
Ferreira
L C S
LC
Ferreira
R C C
RC
D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000502:physiology; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D018441:Biofilms; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D003731:Dental Caries / Q000382:microbiology; D005798:Genes, Bacterial; D006801:Humans; D008074:Lipoproteins / Q000235:genetics / Q000502:physiology; D005810:Multigene Family; D009842:Oligopeptides / Q000378:metabolism*; D009876:Operon; D011994:Recombinant Proteins; D013295:Streptococcus mutans / Q000235:genetics*
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008074:Lipoproteins; D009842:Oligopeptides; D011994:Recombinant Proteins; C046506:oligopeptide-binding protein, bacteria