The application of molecular genetics to the microbiology of dental caries

The introduction of techniques for the manipulation of DNA in vitro has had an enormous impact on progress in every area of biological research. In the case of oral microbiology, the first reports on the application of molecular genetics to streptococci started to appear in the early 1980s, and it is now more than 10 years since the first paper describing cloning and expression of a gene from Streptococcus mutans in another bacterium was published. The purpose of this review is not to provide a resumé of all the work that has been done on the molecular biology of oral bacteria; indeed, we are approaching the stage when a comprehensive survey of work on all oral bacteria is no longer feasible--for instance, over 40 genes have now been cloned and sequenced from S. mutans alone--but rather to illustrate examples of how the new techniques have been applied to give novel approaches and insights into old problems, or expand into new directions. The great majority of published work so far relates to streptococci, and many aspects have been covered in previous review articles [Curtiss, 1985; Russell, 1991], the most recent thorough review being that by Kuramitsu [1993]. Discussion of molecular biology is now so all-pervasive that most readers will be familiar with many of the basic terms, but it may be worth clarifying some of the main points during the course of this article. For total novices, the short book by Brown [1990] forms a useful introduction. A number of recent articles have reviewed recent research on plaque formation [Kolenbrander and London, 1993] and the mutans streptococci in particular [Loesche, 1986], while Freedman et al. [1981] and Tanzer [1992] have summarised the information derived from a genetic approach to oral microbiology before the advent on in vitro manipulation of DNA.