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Applied and Environmental Microbiology, July 1999, p. 3192-3204, Vol. 65, No. 7
School of Oceanography, University of
Washington, Seattle, Washington 98195
Received 15 December 1998/Accepted 3 May 1999
The Columbia River estuary is a dynamic system in which estuarine
turbidity maxima trap and extend the residence time of particles and
particle-attached bacteria over those of the water and free-living bacteria. Particle-attached bacteria dominate bacterial activity in the
estuary and are an important part of the estuarine food web.
PCR-amplified 16S rRNA genes from particle-attached and free-living bacteria in the Columbia River, its estuary, and the adjacent coastal
ocean were cloned, and 239 partial sequences were determined. A wide
diversity was observed at the species level within at least six
different bacterial phyla, including most subphyla of the class
Proteobacteria. In the estuary, most particle-attached
bacterial clones (75%) were related to members of the genus
Cytophaga or of the
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Phylogenetic Analysis of Particle-Attached and Free-Living
Bacterial Communities in the Columbia River, Its Estuary, and the
Adjacent Coastal Ocean
,
, or
subclass of the class
Proteobacteria. These same clones, however, were rare in or
absent from either the particle-attached or the free-living bacterial
communities of the river and the coastal ocean. In contrast, about half
(48%) of the free-living estuarine bacterial clones were similar to
clones from the river or the coastal ocean. These free-living bacteria
were related to groups of cosmopolitan freshwater bacteria
(
-proteobacteria, gram-positive bacteria, and
Verrucomicrobium spp.) and groups of marine organisms
(gram-positive bacteria and
-proteobacteria [SAR11 and
Rhodobacter spp.]). These results suggest that rapidly growing particle-attached bacteria develop into a uniquely adapted estuarine community and that free-living estuarine bacteria are similar
to members of the river and the coastal ocean microbial communities.
The high degree of diversity in the estuary is the result of the mixing
of bacterial communities from the river, estuary, and coastal ocean.
*
Corresponding author. Mailing address: School of
Oceanography, University of Washington, Seattle, WA 98195. Phone: (206)
543-0147. Fax: (206) 543-0275. E-mail:
bcrump{at}u.washington.edu.
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