Amino acid uptake by marine phytoplankters1,2

Wheeler, Patricia A.; North, Barbara B.; Stephens, Grover C.

doi:10.4319/lo.1974.19.2.0249

Cited by 150 publications

(71 citation statements)

References 17 publications

(3 reference statements)

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“…Although DFAAs represent a small fraction of DON produced by phytoplankton (13 to 30 O/O: Braven et al 1984), their rate of uptake and their rSle as nutrients for phytoplankton and bacteria are well documented (e.g. Crawford et al 1974, Wheeler et al 1974, Fuhrman 1987. In particular, GLU and GLN are known to be rapidly and selectively utilized by bacteria (e.g.…”

Section: Resultsmentioning

confidence: 99%

Inefficient feeding by Calanus helgolandicus and Temora longicornis on Coscinodiscus wailesii: quantitative estimation using chlorophyll-type pigments and effects on dissolved free amino acids

Roy¹,

Harris²,

Poulet³

1989

Mar. Ecol. Prog. Ser.

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Section: Resultsmentioning

confidence: 99%

Inefficient feeding by Calanus helgolandicus and Temora longicornis on Coscinodiscus wailesii: quantitative estimation using chlorophyll-type pigments and effects on dissolved free amino acids

Roy¹,

Harris²,

Poulet³

1989

Mar. Ecol. Prog. Ser.

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“…Presence of cell death in bacteria and algae suggests that this phenomenon arose early in evolutionary history. Although the occurrence of bacterial and protozoan cell death has fostered the idea that it is adaptive or "altruistic" in the sense that surviving cells benefit from the organic compounds released by dying ones (Yarmolinsky 1995;Welburn et al 1997), autolysis in an obligate autotroph such as Dunaliella (which cannot benefit from organic molecules; see Wheeler et al 1974) would require a very different interpretation.…”

Section: Discussionmentioning

confidence: 99%

Physiological stress and cell death in marine phytoplankton: Induction of proteases in response to nitrogen or light limitation

Berges

Falkowski

1998

Limnology & Oceanography

276

208

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The physiological processes of natural phytoplankton mortality due to environmental stress (vs. that caused by sedimentation and predation) are poorly understood. Cell survival was examined in batch cultures of the diatom Thalassiosira weissjogii and the chlorophyte Dunaliella tertiolecta during deprivation of fixed nitrogen or light. Despite severe impairment of photosynthetic efficiencies, both species remained viable during 2 weeks of N starvation. Under N stress, a specific protease was induced in the diatom, overall activity of proteases doubled, and there was gradual, selective loss of certain proteins, especially ribulose 1,5bisphosphate carboxylase/oxygenase. Light-deprived diatoms were virtually unaffected, but the chlorophyte underwent catastrophic cell death after about 6 d of darkness. Cell death coincided with a large increase in protease activity and the induction of a specific protease. Although we cannot completely rule out roles for viruses or bacteria in the losses of cells, the consistent timing, the unique response to stress, and the coincident expression of a specific protease strongly suggest that the process is a form of autocatalyzed cell death, such as apoptosis. While of uncertain adaptive significance, phytoplankton cell death may have implications for species succession and cycling of organic matter in aquatic ecosysterns.

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“…Laboratory studies have shown that both groups of organisms can use either organic or inorganic forms of nitrogen as their sole nitrogen source (Brown 1980;Wheeler et al 1974). Our major interest from an ecological viewpoint was to determine the major sources for heterotrophic bacteria in natural populations.…”

Section: Discussionmentioning

confidence: 99%

Utilization of inorganic and organic nitrogen by bacteria in marine systems1

Wheeler

Kirchman

1986

Limnology & Oceanography

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369

241

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The relative contribution of various inorganic and organic forms of nitrogen to the nitrogen requirements of picoplankton was examined with 15N tracers. Size fractionation was used to measure uptake by < l-pm size microorganisms, and inhibitors of protein synthesis were used to separate procaryotic from eucaryotic nitrogen uptake, Picoplankton utilized mainly ammonium and amino acids and only negligible amounts of nitrate and urea. Nearly all amino acid uptake was by procaryotes, while both procaryotes and eucaryotes utilized ammonium. About 78% of total ammonium uptake was by procaryotes, and a significant portion of this was due specifically to heterotrophic bacteria. Regeneration of ammonium was correlated with eucaryotic rather than procaryotic activity. Ammonium accounted for at least 20-60% of the summed ammonium plus amino acid utilization by bacteria. The results suggest that a significant portion of ammonium uptake in the euphotic zone was by heterotrophic bacteria rather than solely by phytoplankton. This may invalidate the use of the Rcdfield C : N ratio for estimating rates of nitrogen assimilation in the euphotic zone from carbon assimilation rates.

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Amino acid uptake by marine phytoplankters1,2

Cited by 150 publications

References 17 publications

Inefficient feeding by Calanus helgolandicus and Temora longicornis on Coscinodiscus wailesii: quantitative estimation using chlorophyll-type pigments and effects on dissolved free amino acids

Inefficient feeding by Calanus helgolandicus and Temora longicornis on Coscinodiscus wailesii: quantitative estimation using chlorophyll-type pigments and effects on dissolved free amino acids

Physiological stress and cell death in marine phytoplankton: Induction of proteases in response to nitrogen or light limitation

Utilization of inorganic and organic nitrogen by bacteria in marine systems1

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