Streptococcus mutans: a new Gram-positive paradigm?

Abstract

Despite the enormous contributions of the bacterial paradigms Escherichia coli and Bacillus subtilis to basic and applied research, it is well known that no single organism can be a perfect representative of all other species. However, given that some bacteria are difficult, or virtually impossible, to cultivate in the laboratory, that some are recalcitrant to genetic and molecular manipulation, and that others can be extremely dangerous to manipulate, the use of model organisms will continue to play an important role in the development of basic research. In particular, model organisms are very useful for providing a better understanding of the biology of closely related species. Here, we discuss how the lifestyle, the availability of suitable in vitro and in vivo systems, and a thorough understanding of the genetics, biochemistry and physiology of the dental pathogen Streptococcus mutans have greatly advanced our understanding of important areas in the field of bacteriology such as interspecies biofilms, competence development and stress responses. In this article, we provide an argument that places S. mutans, an organism that evolved in close association with the human host, as a novel Gram-positive model organism.

Fig. 1.

Areas in the microbiology field that strongly benefited from studies conducted with S. mutans.

Fig. 2.

EPS matrix (red) creates compartmentalized bacterial (green) islets and heterogeneous microenvironments in oral biofilms. Bacterial islets enmeshed and surrounded by an intricate EPS matrix (as seen in the cross-sectional image) were identified across the 3D architecture of a mature mixed-species oral biofilm grown in sucrose. The assembly of a complex network of compartmentalized microenvironments created a range of acidic pockets and localized antimicrobial resistance within the greater biofilm architecture, which illustrates the spatial heterogeneities in the microstructure of biofilm.