Effects of Oxygen on Virulence Traits ofStreptococcus mutans

Abstract

Oxygen profoundly affects the composition of oral biofilms. Recently, we showed that exposure of Streptococcus mutans to oxygen strongly inhibits biofilm formation and alters cell surface biogenesis. To begin to dissect the underlying mechanisms by which oxygen affects known virulence traits of S. mutans, transcription profiling was used to show that roughly 5% of the genes of this organism are differentially expressed in response to aeration. Among the most profoundly upregulated genes were autolysis-related genes and those that encode bacteriocins, the ClpB protease chaperone subunit, pyruvate dehydrogenase, the tricarboxylic acid cycle enzymes, NADH oxidase enzymes, and certain carbohydrate transporters and catabolic pathways. Consistent with our observation that the ability of S. mutans to form biofilms was severely impaired by oxygen exposure, transcription of the gtfB gene, which encodes one of the primary enzymes involved in the production of water-insoluble, adhesive glucan exopolysaccharides, was down-regulated in cells growing aerobically. Further investigation revealed that transcription of gtfB, but not gtfC, was responsive to oxygen and that aeration causes major changes in the amount and degree of cell association of the Gtf enzymes. Moreover, inactivation of the VicK sensor kinase affected the expression and localization the GtfB and GtfC enzymes. This study provides novel insights into the complex transcriptional and posttranscriptional regulatory networks used by S. mutans to modulate virulence gene expression and exopolysaccharide production in response to changes in oxygen availability.

Streptococcal Antagonism in Oral Biofilms:Streptococcus sanguinisandStreptococcus gordoniiInterference withStreptococcus mutans

“…The expression of the competence genes in S. mutans is coordinated with the expression of a group of bacteriocins and bacteriocin-like genes (19); accordingly, the expression of the bacteriocin mutacin IV was elevated under aerobic conditions in our studies. During the preparation of the present study, Ahn et al (3) reported the oxygen-dependent upregulation of the mutacin IV gene and the competence system for S. mutans using DNA microarrays, further supporting our results. Mutacin IV was shown to be involved in the lysis and release of plasmid DNA from S. gordonii (17).…”

Photodynamic Effects of Curcumin Against Cariogenic Pathogens

“…The oxygen modulates the expression of a variety of genes in S. mutans, many of which participate in the formation of a biofilm or can contribute to virulence in some other way. 44 It is known that during photodynamic inactivation, a number of reactive oxygen species (ROS) are generated. S. mutans responds to environmental stresses caused by oxidation, heat, acidity, and salinity or by specific or coordinated regulations of the protein levels.…”

The Role of CRISPR-Cas Systems in Virulence of Pathogenic Bacteria

“…In Streptococcus mutans, the causative agent of tooth decay, mutations in virulence or global regulatory genes (including genes involved in stress responses) strongly affect gene transcription (81)(82)(83)(84)(85), including that of the type II cas genes ( Fig. 1 and 4).…”