Contribution of dissolved free amino acids and ammonium to the nitrogen requirements of heterotrophic bacterioplankton

Keil, RG; Kirchman, DL

doi:10.3354/meps073001

Cited by 170 publications

(127 citation statements)

References 22 publications

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“…R 2 of the regression to calculate K t ϩ S n was Ͼ0.93. Even though we did not test the validity of the protein uptake kinetics, data from Keil and Kirchman (1993) indicate that uptake kinetics of various types of defined labile proteins and extracted protein from algae are similar.…”

Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

“…The DCAA pool is chemically complex and is composed of various types of combined amino acids, including oligo-and polypeptides, protein, and amino acids bound to humic substances (Keil and Kirchman 1993;Hubberten et al 1994). Even though labile protein accounts for Ͻ10% of DCAAs, it can support 20%-65% of the bacterial N demand (Keil and Kirchman 1999).…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…Much is known about the turnover of dissolved free amino acids (DFAAs) and their significance for the growth of heterotrophic bacteria (e.g., Jørgensen 1987;Simon and Rosenstock 1992). Several studies found that DFAAs and ammonium are the primary N sources for bacteria (Keil and Kirchman 1991;Jørgensen et al 1993;Middelboe et al 1995a), whereas others showed that dissolved combined amino acids (DCAAs) are of similar or even higher significance for the growth of bacterioplankton (Coffin 1989;Rosenstock and Simon 1993;Kroer et al 1994). The DCAA pool is chemically complex and is composed of various types of combined amino acids, including oligo-and polypeptides, protein, and amino acids bound to humic substances (Keil and Kirchman 1993;Hubberten et al 1994).…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…Therefore, incorporation of 14 C protein was measured at four concentrations (1, 20, 50, and 100 nM final concentration). Incubation and further processing was done as described for measurements of BP, and S n was calculated as 50% of K t ϩ S n (Billen 1991;Keil and Kirchman 1993). R 2 of the regression to calculate K t ϩ S n was Ͼ0.93.…”

Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

“…This custom-made protein, extracted from Anacystis nidulans (Keith et al 1974), also constituted 40% of oligo-peptides of Ͻ3 kDa and served as a model substrate for labile proteins of a wide range in MW and typical under natural conditions. For calculation of the specific activity, the protein concentration in the stock solution was determined by the bicinchoninic acid method (Keil and Kirchman 1993). The radiolabel was added in triplicate to 6-ml subsamples and a Formalin-killed control not exceed-ing one tenth of the in situ concentration: 0.8-1.7 nM final concentration for 3 H DFAAs and 0.7-3 nM for 14 C protein.…”

Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

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Sources and sinks of dissolved free amino acids and protein in a large and deep mesotrophic lake

Rosenstock

Simon

2001

Limnology & Oceanography

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We studied the microbial cycling of dissolved free amino acids (DFAAs) and protein in mesotrophic Lake Constance, Germany, by examining their release by phytoplankton and various heterotrophic organisms and incorporation by heterotrophic bacterioplankton. Release processes of both substrate classes, measured by an isotope dilution approach, comprised, as an annual mean, 15% of primary production and as much as 64% during the clearwater phase. DFAAs accounted for ϳ70% of total release during the spring bloom, in the early phase predominantly as photosynthetic extracellular products of rapidly growing algae and toward the end as a result of copepod grazing. Thereafter, during the clear-water phase, when daphnids were most abundant, release was dominated by protein. At this time, and again in late summer, lysis of grazing-damaged and senescent algae, including as well the hydrolytic activity of attached bacteria was one of the most important sources of protein. Rotifers, protozoans, and release processes in the fraction Ͻ1 m were minor sources of DFAA ϩ protein. Concentrations of dissolved combined amino acids (DCAAs) and protein ranged between 750-1,900 and 1-280 nM, respectively, and peaked during phytoplankton blooms in spring and summer. As an annual mean, concentrations of labile protein constituted 8% of DCAAs, and the ratio of DFAAs to DCAAs was 0.16. About 50% of the DCAAs occurred in the molecular weight fraction between DFAA and 3 kDa and 30% in that Ͼ30 kDa. Concentrations of DCAAs Ͼ3 kDa were closely correlated to chlorophyll a, suggesting their phytoplankton origin and thus a ready availability. Protein was the preferred bacterial substrate. As an annual mean, its incorporation supported 45% of bacterial biomass production, compared with 13% by DFAAs. During winter and spring, when DFAA concentrations were highest, DFAA incorporation constituted up to 40% of bacterial production. Annually, the sum of DFAA ϩ protein supported 58% and 80% of the bacterial C and N demand, respectively, indicating that they were the most important bacterial C and N sources.

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Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

Section: Acknowledgmentsmentioning

confidence: 99%

Section: Acknowledgmentsmentioning

confidence: 99%

Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

Section: Incorporation Of Amino Acids and Protein-incorporationmentioning

confidence: 99%

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Sources and sinks of dissolved free amino acids and protein in a large and deep mesotrophic lake

Rosenstock

Simon

2001

Limnology & Oceanography

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Resource Control of Bacterial Dynamics in the Sea

Church

2008

Microbial Ecology of the Oceans

116

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Competition between photochemical and biological degradation of dissolved organic matter from the cyanobacteria Microcystis aeruginosa

Bittar

Vieira

Stubbins

et al. 2015

Limnology & Oceanography

126

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Extracellular and intracellular dissolved organic matter (E‐DOM and I‐DOM, respectively) produced in axenic cultures by the cosmopolitan cyanobacteria Microcystis aeruginosa were characterized, and photoreactivity, bioreactivity, and the effects of phototransformations on bioavailability of E‐DOM and I‐DOM were assessed in laboratory experiments. Chromophoric (CDOM) and fluorescent (FDOM) properties were analyzed by spectrophotometry, and chemical signatures were obtained by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS). E‐DOM was more heterogeneous regarding optical characteristics as indicated by the presence of multiple CDOM peaks and the more even distribution of FDOM components, and had less absolute and relative numbers for molecular formulae containing nitrogen (N) than I‐DOM. E‐DOM was more photolabile, with greater photochemical removal of dissolved organic carbon (DOC), CDOM and FDOM, and exhibited more pronounced photochemical alterations in molecular formulae composition than I‐DOM. E‐DOM was less biolabile, with less biological removal of DOC, CDOM, and protein‐like fluorescent material, and supported lower rates of bacterial productivity than I‐DOM. Phototransformations reduced the bioavailability of E‐DOM and I‐DOM, as shown by lower bacterial productivity and longer DOC and CDOM half‐lives in bioassays with photoirradiated DOM in comparison to those with nonirradiated DOM. Analyses of CDOM, FDOM, and FTICR‐MS revealed that the decrease in bioavailability was caused primarily by photolysis of the biolabile DOM, indicating competition between photochemical and biological removal of cyanobacterial DOM. These results provided insights into mechanistic effects of independent and combined photochemical and biological degradation on M. aeruginosa‐derived DOM.

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Contribution of dissolved free amino acids and ammonium to the nitrogen requirements of heterotrophic bacterioplankton

Cited by 170 publications

References 22 publications

Sources and sinks of dissolved free amino acids and protein in a large and deep mesotrophic lake

Sources and sinks of dissolved free amino acids and protein in a large and deep mesotrophic lake

Resource Control of Bacterial Dynamics in the Sea

Competition between photochemical and biological degradation of dissolved organic matter from the cyanobacteria Microcystis aeruginosa

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