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Journal of Bacteriology, June 2001, p. 3770-3783, Vol. 183, No. 12
Department of Molecular Genetics, The Forsyth
Institute,1 and
Department of Oral Biology, Harvard School
of Dental Medicine,2 Boston, Massachusetts
Received 8 November 2000/Accepted 28 March 2001
The purpose of this study was to determine the bacterial diversity
in the human subgingival plaque by using culture-independent molecular
methods as part of an ongoing effort to obtain full 16S rRNA sequences
for all cultivable and not-yet-cultivated species of human oral
bacteria. Subgingival plaque was analyzed from healthy subjects and
subjects with refractory periodontitis, adult periodontitis, human
immunodeficiency virus periodontitis, and acute necrotizing ulcerative
gingivitis. 16S ribosomal DNA (rDNA) bacterial genes from DNA isolated
from subgingival plaque samples were PCR amplified with all-bacterial
or selective primers and cloned into Escherichia coli.
The sequences of cloned 16S rDNA inserts were used to determine species
identity or closest relatives by comparison with sequences of known
species. A total of 2,522 clones were analyzed. Nearly complete
sequences of approximately 1,500 bases were obtained for putative new
species. About 60% of the clones fell into 132 known species, 70 of
which were identified from multiple subjects. About 40% of the clones
were novel phylotypes. Of the 215 novel phylotypes, 75 were identified
from multiple subjects. Known putative periodontal pathogens such as
Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola were
identified from multiple subjects, but typically as a minor component
of the plaque as seen in cultivable studies. Several phylotypes fell
into two recently described phyla previously associated with extreme
natural environments, for which there are no cultivable species. A
number of species or phylotypes were found only in subjects with
disease, and a few were found only in healthy subjects. The organisms
identified only from diseased sites deserve further study as potential
pathogens. Based on the sequence data in this study, the predominant
subgingival microbial community consisted of 347 species or phylotypes
that fall into 9 bacterial phyla. Based on the 347 species seen in our
sample of 2,522 clones, we estimate that there are 68 additional unseen
species, for a total estimate of 415 species in the subgingival plaque.
When organisms found on other oral surfaces such as the cheek, tongue,
and teeth are added to this number, the best estimate of the total
species diversity in the oral cavity is approximately 500 species, as
previously proposed.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.12.3770-3783.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Bacterial Diversity in Human Subgingival
Plaque
*
Corresponding author. Mailing address: The Forsyth
Institute, 140 Fenway, Boston, MA 02115. Phone: (617) 262-5200, ext.
288. Fax: (617) 262-4021. E-mail: bpaster{at}forsyth.org.
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