Tc. Gsell et al., CHARACTERIZATION OF THE SEDIMENT BACTERIAL COMMUNITY IN GROUNDWATER DISCHARGE ZONES OF AN ALKALINE FEN - A SEASONAL STUDY, Applied and environmental microbiology, 63(8), 1997, pp. 3111-3118
The cell density, activity, and community structure of the bacterial c
ommunity in wetland sediments were monitored over a 13-month period. T
he study was performed at Cedar Bog, an alkaline fen. The objective wa
s to characterize the relationship between the sediment bacterial comm
unity in groundwater upwelling zones and the physical and chemical fac
tors which might influence the community structure and activity. DNA,
protein, and lipid synthesis were measured at three different upwellin
g zones by using [H-3]thymidine, [C-14]leucine, and [C-14]glucose inco
rporation, respectively. The physiological status (apparent stress) of
the consortium was assessed by comparing [C-14]glucose incorporation
into membrane and that into storage lipids. Bacterial cell density was
determined by acridine orange direct counts, and gross bacterial comm
unity structure was determined by bisbenzimidazole-cesium chloride gra
dient analysis of total bacterial community DNA. Both seasonal and sit
e-related covariation were observed in all estimates of bacterial biom
ass and activity. Growth rate estimates and cell density peaked in lat
e July at 2.5 x 10(8) cells/g/day and 2.7 x 10(9) cells/g, respectivel
y, 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 ratio
s were generally highest in late spring and peaked in September for on
e site. Overall, the data indicate dynamic seasonal differences in sed
iment bacterial community activity and physiology, possibly in respons
e to changing physical and chemical environmental factors which includ
ed the C/N/P ratios of the perfusing groundwater. By contrast, total c
ell numbers were rather constant, and community structure analysis ind
icated that the overall community structure was similar throughout the
study.