Abstract
The development of complex multispecies communities such as biofilms is controlled by interbacterial communication systems. We have previously reported an intergeneric communication between two oral bacteria, Streptococcus cristatus and Porphyromonas gingivalis, that results in inhibition of fimA expression. Here, we demonstrate that a surface protein, arginine deiminase (ArcA), of S. cristatus serves as a signal that initiates intergeneric communication. An ArcA-deficient mutant of S. cristatus is unable to communicate with P. gingivalis. Furthermore, arginase activity is not essential for the communication, and ArcA retains the ability to repress expression of fimA in the presence of arginine deiminase inhibitors. These results present a novel mechanism by which intergeneric communication in dental biofilms is accomplished.
Highlights
Human dental plaque is a multispecies microbial biofilm that is associated with two common oral diseases, dental caries and periodontal disease
We reported previously that the expression of the fimA gene is repressed in the presence of surface extracts of S. cristatus, but not in the culture medium, indicating the presence of a LuxS-independent intergeneric communication system (Xie et al, 2000)
The non-bound proteins were collected from the column and the fractions were analysed by SDS-PAGE. To test their ability to repress fimA expression in P. gingivalis, each fraction was mixed with P. gingivalis UPF, a strain carrying a fimA promoter– lacZ fusion
Summary
Human dental plaque is a multispecies microbial biofilm that is associated with two common oral diseases, dental caries and periodontal disease. Formation of dental plaque is initiated by Grampositive species, including streptococci and Actinomyces spp., which recognize salivary receptors exposed on the tooth surfaces (Gibbons et al, 1991; Li et al, 2000; Scannapieco et al, 1995). These early colonizers in turn provide new surfaces that attract and recruit succeeding organisms including Gram-negative potential pathogens, such as Porphyromonas gingivalis and Aggregatibacter (Actinobacillus) actinomycetemcomitans (Kolenbrander et al, 2002). The early colonizers play a key role in the development of the dental plaque biofilm
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