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Appl. Environ. Microbiol., 08 1997, 3111-3118, Vol 63, No. 8
TC Gsell, WE Holben and RM Ventullo
The cell density, activity, and community structure of the bacterial
community in wetland sediments were monitored over a 13-month period. The
study was performed at Cedar Bog, an alkaline fen. The objective was to
characterize the relationship between the sediment bacterial community in
groundwater upwelling zones and the physical and chemical factors which
might influence the community structure and activity. DNA, protein, and
lipid synthesis were measured at three different upwelling zones by using
[3H]thymidine, [14C]leucine, and [14C]glucose incorporation, respectively.
The physiological status (apparent stress) of the consortium was assessed
by comparing [14C]glucose incorporation into membrane and that into storage
lipids. Bacterial cell density was determined by acridine orange direct
counts, and gross bacterial community structure was determined by
bisbenzimidazole-cesium chloride gradient analysis of total bacterial
community DNA. Both seasonal and site-related covariation were observed in
all estimates of bacterial biomass and activity. Growth rate estimates and
cell density peaked in late July at 2.5 x 10(8) cells/g/day and 2.7 x 10(9)
cells/g, respectively, and decreased in December to 2.0 x 10(7) cells/g/day
and 1.5 x 10(9) cells/g, respectively. Across sites, membrane-to-storage-
lipid ratios were generally highest in late spring and peaked in September
for one site. Overall, the data indicate dynamic seasonal differences in
sediment bacterial community activity and physiology, possibly in response
to changing physical and chemical environmental factors which included the
C/N/P ratios of the perfusing groundwater. By contrast, total cell numbers
were rather constant, and community structure analysis indicated that the
overall community structure was similar throughout the study.
Copyright © 1997, American Society for Microbiology
Characterization of the sediment bacterial community in groundwater discharge zones of an alkaline fen: a seasonal study
Department of Biology, University of Dayton, Ohio 45469-2320, USA. tgsell@selway.umt.edu
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