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Appl. Environ. Microbiol., Mar 1995, 944-952, Vol 61, No. 3
KD Bidle and M Fletcher
Free-living and particle-associated bacterial communities in the Chesapeake
Bay estuary were analyzed and compared by using acridine orange direct
counts and low-molecular-weight (LMW) RNA analysis. Samples were taken from
top and bottom waters at upper- and mid-bay sites in December 1992.
Free-living bacteria dominated the bacterial numbers at all sampling sites,
although particle-associated bacteria increased in areas with greater
particle loads. LMW RNAs (5S rRNA and tRNA) obtained directly from
free-living, particle-associated, and total bacterioplankton communities
were analyzed by high-resolution electrophoresis. There were distinct
differences in the migration distances between LMW RNAs of free-living and
particle-associated communities taken from the same site, indicating that
the two communities differ in composition. In addition, LMW RNA profiles
differed minimally with depth for all of the communities examined,
presumably because of vertical mixing. 5S rRNAs of free-living communities
from the upper- and mid-bay regions differed considerably.
Particle-associated RNAs, on the other hand, were very similar, suggesting
consistent environmental conditions on particles that select for similar
community members. Lastly, several isolated bacteria had 5S rRNAs that were
not detected in their respective extracted community 5S rRNAs, indicating
that these isolated organisms were not representative of dominant members.
Copyright © 1995, American Society for Microbiology
Comparison of Free-Living and Particle-Associated Bacterial Communities in the Chesapeake Bay by Stable Low-Molecular-Weight RNA Analysis
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, University of Maryland System, Baltimore, Maryland 21202
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