Different patterns of growth and nitrogen uptake in two clones of marineSynechococcus spp. |
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Authors: | P M Glibert R T Ray |
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Institution: | (1) Horn Point Environmental Laboratories, University of Maryland, P.O. Box 775, 21613 Cambridge, Maryland, USA;(2) Present address: State Water Control Board, Office of Environmental Research and Standards, P.O. Box 11143, 23230 Richmond, Virginia, USA |
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Abstract: | We grew marineSynechococcus Clones WH7803 and WH8018 at 150µE m–2 s–1 in dilute batch cultures with NH
4
+
as the limiting nutrient. The maximal uptake capacities for NH
4
+
and NO
3
-
were measured in frequent experiments during log and stationary phases of growth. Clone WH7803, originally isolated from oceanic waters, had a specific uptake rate of NH
4
+
that approximated the maximum (log phase) specific growth rate (ca ~ 0.025 h–1). NO
3
-
uptake was observed only after nitrogen in the media was depleted; the NO
3
–
uptake capacity was ca 12% the capacity for NH
4
+
uptake throughout the nitrogen depleted period. Growth was arrested upon nitrogen depletion, but resumed soon after reinoculation into fresh media, even after 5 d of starvation. Clone WH8018, originally isolated from coastal waters, revealed a five-fold enhancement in the NH
4
+
uptake rate relative to growth rate at the time of nitrogen depletion. As nitrogen starvation proceeded, this enhancement was reduced. This clone, too, was able to take up NO
3
-
once nitrogen in the media was depleted, but only after ca 20 h. Growth continued for a limited period during nitrogen depletion, but nitrogen-starved cells were slow to recover upon reinoculation into fresh media. We speculate that clonal differences may reflect differences in the molecular regulation of nitrogen assimilation. |
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Keywords: | |
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