Genetic Approaches to The Study of Oral Microflora: A Review

Abstract

As the study of oral microorganisms intensified almost 2 decades ago, the application of genetic techniques resulted in important contributions to the understanding of this clinically and ecologically important group of bacteria. The isolation and characterization of mutants of cariogenic streptococci helped to focus attention on traits that were important in colonization and virulence. Such classic genetic approaches gave way to molecular genetic techniques, including recombinant DNA methodology in the late 1970s. Gene cloning systems and methods to move DNA into cells have been developed for oral streptococci. Many streptococcal genes thought to be important in colonization and virulence have since been cloned and their nucleotide sequence determined. Mutant strains have been constructed using defective copies of cloned genes in order to create specific genetic lesions on the bacterial chromosome. By testing such mutants in animal models, a picture of the cellular and molecular basis of dental caries is beginning to emerge. These modern genetic methodologies also are being employed to develop novel and efficacious cell-free or whole cell vaccines against this infection. Genetic approaches and analyses are now being used to dissect microorganisms important in periodontal disease as well. Such systems should be able to exploit advances made in genetically manipulating related anaerobes, such as the intestinal Bacteroides. Gene cloning techniques in oral anaerobes, Actinomyces and Actinobacillus, are already beginning to pay dividends in helping understand gene structure and expression. Additional effort is needed to develop facile systems for genetic manipulation of these important groups of microorganisms.

Localization of the Fusobacterium nucleatum T18 adhesin activity mediating coaggregation with Porphyromonas gingivalis T22

“…Its importance in dental caries is well documented, and an extensive literature supports the conclusion that streptococcal adherence to the host tooth surface is necessary for the initiation of a carious lesion (11,21).…”

Molecular and Genetic Analyses of Actinomyces SPP

“…The results of such studies also will provide insight into the design of novel approaches to modify plaque formation. Indeed, the use of molecular genetic approaches was instrumental in the analysis of the biochemical, functional, and structural characteristics of various cell-surface antigens and metabolic enzymes from oral streptococci and the regulation of genes that encode these molecules (Macrina et al, 1990;Kuramitsu, 1993;Russell, 1994;lenkinson and Lamont, 1997). Although the genus Actinomyces has been recognized as one of the predominant primary colonizers of the oral cavity for more than two decades, detailed analysis of cell-surface factors that are involved in promoting their adherence and persistence was made possible only recently with the development of a genetic transfer system for these bacteria (Yeung and Kozelsky, 1994).…”

Molecular characterization of a STreptococcus mutans mutant altered in environmental stress responses

“…The first concerns the ability of these organisms to colonize tooth surfaces, while the other involves their strong acidogenicity, which leads to demineralization of enamel surfaces. The sucrose-dependent and -independent colonization factors concerned with the former property have been characterized by using genetic and biochemical approaches (22). Acid tolerance (aciduricity) has also been considered to be an important cariogenic property of S. mutans, and these organisms are known to be among the most acid tolerant of the oral bacteria (15).…”