When these phylotypes were compared

When these phylotypes were compared to a database [13]
containing more than 5000 16S rRNA sequences from
known bacterial species, plus another 2000 sequences isolated
directly from various environments, most were not
sufficiently similar to any sequence in the database for it
to be likely that they were derived from the same species
(Table 1). With the gut bacteria, 62 out of 82 phylotypes
appeared to represent novel species. For the plaque
specimen, 31 out of 59 phylotypes obtained by direct PCR
amplification were novel entities. In contrast, 22 out of 28
of the phylotypes obtained from organisms cultured from
plaque material corresponded to known species. The
advantage of identifying microbes using rRNA sequencebased
methods is evident, as fewer than half of the cultured
plaque bacteria were identified at the species level
by phenotypic methods. The presence of genetically
novel species among even the cultivated plaque bacteria
shows that further efforts to catalog the diversity of
microorganisms that can be grown in the laboratory would
also be useful.