Relman and colleagues [2] have now applied this cultureindependent
methodology to survey bacteria residing in
the subgingival crevice of a healthy person, starting with
plaque scraped from the tooth surface below the gum line.
Ironically, bacteria from this region were among the first
ever observed directly by humans. Over three hundred
years ago, Antony von Leeuwenhoek [9] scraped material
from between his own teeth, and those of other tolerant
townspeople, to examine with his homemade microscopes.
To his surprise and pleasure, he saw ‘very many small
Animals, which moved themselves very extravagantly’. His
drawings portray the spirochaetes, cocci and rod-shaped
bacteria we now know to be associated with plaque. This
microbial community contains many harmless commensal
bacteria, but it also has important effects on oral health.
Fermentative processes in plaque lead to dental caries, and
opportunistic pathogens residing here can cause gingivitis
and periodontitis, and contribute to other serious conditions
[10]. Kroes et al. [2] cultured 28 distinct types of bacteria
from their plaque sample, but could assign species
designations to fewer than half of them using standard
phenotypic methods, reflecting limitations in the current
knowledge about many members of this community.