Critical Reviews in Oral Biology & Medicine, Vol 12, 217-243, Copyright © 2001 by International & American Associations for Dental Research
Genetic competence and transformation in oral streptococci
D. G. Cvitkovitch
Dental Research Institute, University of Toronto, Faculty of Dentistry, ON, Canada. dennis.cvitkovitch@utoronto.ca
The oral streptococci are normally non-pathogenic residents of the human
microflora. There is substantial evidence that these bacteria can, however,
act as "genetic reservoirs" and transfer genetic information to transient
bacteria as they make their way through the mouth, the principal entry
point for a wide variety of bacteria. Examples that are of particular
concern include the transfer of antibiotic resistance from oral
streptococci to Streptococcus pneumoniae. The mechanisms that are used by
oral streptococci to exchange genetic information are not well-understood,
although several species are known to enter a physiological state of
genetic competence. This state permits them to become capable of natural
genetic transformation, facilitating the acquisition of foreign DNA from
the external environment. The oral streptococci share many similarities
with two closely related Gram-positive bacteria, S. pneumoniae and Bacillus
subtilis. In these bacteria, the mechanisms of quorum-sensing, the
development of competence, and DNA uptake and integration are
well-characterized. Using this knowledge and the data available in genome
databases allowed us to identify putative genes involved in these processes
in the oral organism Streptococcus mutans. Models of competence development
and genetic transformation in the oral streptococci and strategies to
confirm these models are discussed. Future studies of competence in oral
biofilms, the natural environment of oral streptococci, will be discussed.
