249
are quite closely affiliated with cultured and well-characterized open-ocean cyanobacteria
(Giovanonni et al., 1990a; Waterbury and Distel, unpublished data). Notably, several
Proteobacterial clones from Central North Pacific bacterioplankton are nearly identical to the
novel, deep-branching Sar 11 cluster from the Sargasso Sea (Giovanonni et al., 1990a;
Schmidt et al., 1990). Partial sequence similarity values between representatives of this
cluster, originating from two different ocean gyres, are remarkably high (0.969 to 0.998, see
Figure Ib).
The preliminary data indicates that at least some of the bacterioplankton from these two
central oceanic gyres are quite closely related, at the near-species level, and that they are
likely globally distributed (Figure 1). These data suggest that phylogenetic distance between
related bacterioplankton within a given ocean gyre is at least as great as that found between
closely related species of different oceanic provinces. These data also support Giovanonni's
hypothesis that the Sar 11 group is an important component of the bacterioplankton. This
novel group may well be cosmopolitan in oligotrophic gyres of the world's oceans. These
results also demonstrate that both the PCR and the shotgun library approaches are viable
options for assessing the phylogenetic diversity of mixed microbial popUlations. The two
different cloning strategies, employed at different times of year on opposite sides of the globe,
have yielded remarkably similar results. The utility of accumulating sequence data bases is
also demonstrated in the comparison of these two data sets. Much more data needs to be
collected to characterize the diversity, variability, activities and abundance of bacterioplankton
species. The use of rRNA specific hybridization probes is one potential tool for detecting and
identifying particular taxa, and estimating their abundance and distribution.
HYBRIDIZATION PROBES AND SINGLE CELL ANALYSIS
The nucleotide sequence of small subunit rRNAs consists of both very conserved, as well as
more variable, nucleotide positions. Some short regions of rRNA sequence are invariant
between distantly related taxa (Lane et al., 1985; Giovanonni et at., 1988). Other more
variable regions are unique to individual species (Stahl et al., 1988; DeLong et al., 1989a;
Amman et al., 1990a; Tsien et al., 1990). These short, contiguous segments ("" 20 nucleotides
in length) of rRNA sequence can serve as targets for rRNA-specific, nucleic acid
are quite closely affiliated with cultured and well-characterized open-ocean cyanobacteria
(Giovanonni et al., 1990a; Waterbury and Distel, unpublished data). Notably, several
Proteobacterial clones from Central North Pacific bacterioplankton are nearly identical to the
novel, deep-branching Sar 11 cluster from the Sargasso Sea (Giovanonni et al., 1990a;
Schmidt et al., 1990). Partial sequence similarity values between representatives of this
cluster, originating from two different ocean gyres, are remarkably high (0.969 to 0.998, see
Figure Ib).
The preliminary data indicates that at least some of the bacterioplankton from these two
central oceanic gyres are quite closely related, at the near-species level, and that they are
likely globally distributed (Figure 1). These data suggest that phylogenetic distance between
related bacterioplankton within a given ocean gyre is at least as great as that found between
closely related species of different oceanic provinces. These data also support Giovanonni's
hypothesis that the Sar 11 group is an important component of the bacterioplankton. This
novel group may well be cosmopolitan in oligotrophic gyres of the world's oceans. These
results also demonstrate that both the PCR and the shotgun library approaches are viable
options for assessing the phylogenetic diversity of mixed microbial popUlations. The two
different cloning strategies, employed at different times of year on opposite sides of the globe,
have yielded remarkably similar results. The utility of accumulating sequence data bases is
also demonstrated in the comparison of these two data sets. Much more data needs to be
collected to characterize the diversity, variability, activities and abundance of bacterioplankton
species. The use of rRNA specific hybridization probes is one potential tool for detecting and
identifying particular taxa, and estimating their abundance and distribution.
HYBRIDIZATION PROBES AND SINGLE CELL ANALYSIS
The nucleotide sequence of small subunit rRNAs consists of both very conserved, as well as
more variable, nucleotide positions. Some short regions of rRNA sequence are invariant
between distantly related taxa (Lane et al., 1985; Giovanonni et at., 1988). Other more
variable regions are unique to individual species (Stahl et al., 1988; DeLong et al., 1989a;
Amman et al., 1990a; Tsien et al., 1990). These short, contiguous segments ("" 20 nucleotides
in length) of rRNA sequence can serve as targets for rRNA-specific, nucleic acid