The phylogenetic diversity of two continental shelf picoplankton
communities was examined by analyzing SSU (16S) ribosomal RNA (rRNA)
genes amplified from environmental DNA with bacterial-specific primers and
the polymerase chain reaction (PCR). Picoplankton populations collected from
the pycnocline (10 m) over the eastern continental shelf of the United States
near Cape Hatteras, North Carolina, and surface seawater (10 m) from the
western continental shelf of the United States 8 km west of Yaquina Head,
Oregon, served as sources of bulk nucleic acids used in this study. A total of
285 SSU rRNA gene clones were analyzed in the two libraries, more than
doubling the number previously available from seawater samples. In contrast
to previous studies of bacterioplankton diversity from the open-ocean, a large
proportion of the rDNA clones recovered in this study (38%) were related to
plastid SSU rRNA genes, including plastids from bacillariophyte,
prymnesiophyte, cryptophyte, chrysophyte, and prasinophyte algae, as well as
a number of unique plastid rRNA gene clones for which no close phylogenetic
relatives were discovered. A majority of the bacterial gene clones recovered (72% of bacterial clones) were closely related to rRNA gene lineages
discovered previously in clone libraries from open-ocean marine habitats,
including the SAR86 cluster (�� Proteobacteria), SAR83, SAR11, and SAR116
clusters (all �� Proteobacteria), the marine Gram-positive cluster
(Actinomycetes), the marine group A/SAR406 cluster, and a cluster of
environmental clones within the flexibacter-cytophaga-bacteroides phylum. A
majority of the remaining bacterial clones were phylogenetically related to the
�� and �� subclasses of the Proteobacteria, including an rDNA lineage within the
Type I methylotroph Glade of the �� subclass. The abundance of plastid rDNAs
and the lack of cyanobacterial-related clones, as well as the presence of ��
Proteobacteria, are features of these coastal picoplankton gene clone libraries
which distinguish them from similar studies of oligotrophic open-ocean sites.
Overall, however, these data indicate that a limited number of as yet
uncultured bacterioplankton lineages, related to those previously observed in
the open-ocean, can account for the majority of cells in these coastal marine
bacterioplankton assemblages. / Graduation date: 1998
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34142 |
| Date | 21 May 1997 |
| Creators | Rapp��, Michael Stephen |
| Contributors | Giovannoni, Stephen J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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