Dissolved free amino acids in the Sargasso Sea: uptake and respiration rates, turnover times, and concentrations

Suttle, CA; Chan, Amy M.; Fuhrman, Jed A.

doi:10.3354/meps070189

Cited by 114 publications

(106 citation statements)

References 33 publications

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“…Thus, production rates are comparable between the two concentrations, but saturation does lean toward overestimation in the oligotrophic open ocean. Since leucine biosynthesis in the presence of ambient additions would be higher than at saturating concentration (Kirchman et al 1985), and underestimates of uptake rates are most pronounced at lower substrate additions (Suttle et al 1991), growth rates determined using 0.4 nmol L 21 3 H-leucine or 14 C-leucine would be conservative estimates. Leucine assimilation efficiency-calculated from uptake/ (uptake + respiration)-was estimated at 94.5% 6 3.7% and 84.8% 6 7.9% using 0.4 nmol L 21 and 20 nmol L 21 14 C-leucine, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Crawford et al (1974) also reported that leucine was respired the slowest of the amino acids studied in an estuary. Suttle et al (1991) postulated that the small portion of respired leucine was a result of mechanismleucine being directly shuttled into protein synthesis making it unavailable to respiratory pathways-rather than selectivity for less valuable and rare commodities for energy production. However, we suggest that the planktonic bacteria use leucine as a carbon source when it is present at saturating concentrations and, therefore, surplus to protein requirements; but, at ambient concentrations, they selectively reserve leucine for protein synthesis.…”

Section: Discussionmentioning

confidence: 99%

“…However, the biggest influence is most likely the concentration of 14 Cleucine applied to samples. Suttle et al (1991) made additions of 0.1 to ''a few'' nmol L 21 3 H-leucine and measured just 4.6% 6 7.0% and 2.2% 6 8.7% respiration to 3 H 2 O in two separate studies conducted in the Sargasso Sea. Furthermore, they measured similarly low respiration of orthinine, an amino acid important in the synthesis of polyamines; yet typically 60-80% of the most abundant amino acids (glutamate, alanine, glycine, and serine) was respired and , 60% of glucose.…”

Section: Discussionmentioning

confidence: 99%

“…These studies used saturating 14 C-leucine additions. Conversely, Suttle et al (1991) measured , 10% respiration of close to ambient concentration 3 H-leucine additions in the Sargasso Sea. Thus, we hypothesized that, in the open Atlantic Ocean at least, the bacterioplankton does not respire high proportions of leucine at ambient bioavailable concentration, but rather the high respiration rates measured were a consequence of leucine saturation, which led to a response of the bacterioplankton to nutrient addition.…”

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confidence: 99%

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Low microbial respiration of leucine at ambient oceanic concentration in the mixed layer of the central Atlantic Ocean

Hill

Warwick

Zubkov

2013

Limnology & Oceanography

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Bacterioplankton are the primary consumers of dissolved organic matter in the ocean, thus the quantification of bacterioplankton production (BP) is essential to our understanding of carbon cycling in the largest ecosystems on Earth. We compared BP, measured as the rate of 14 C-leucine or 3 H-leucine uptake at close to saturating concentration (20 nmol L 21 ), with ambient uptake measured from dilution bioassays. We hypothesized that saturation with leucine would lead to its respiration as a carbon source, thereby not truly representing ambient BP. Seawater was collected from the photic zone throughout the Atlantic Ocean. Respiration as a proportion of total consumption (uptake + respiration) of close to ambient (0.4 nmol L 21 ) and close to saturating (20 nmol L 21 ) 14 C-leucine concentrations were compared. Saturating 3 H-leucine additions overestimated ambient leucine uptake at low rates (200% 6 100% ambient) and underestimated uptake at high rates (90% + 20% ambient). The proportion of total leucine uptake that was respired was threefold higher for 20 nmol L 21 14 C-leucine additions than 0.4 nmol L 21 14 C-leucine additions (15% 6 8% and 5% 6 4%, respectively). Consequently, microbial efficiency of leucine assimilation-an indicator of bacterioplankton growth efficiency-was significantly higher and more stable at close to ambient 14 C-leucine additions than at saturating concentrations (95% 6 4% and 85% 6 8%, respectively). Thus, saturation of oligotrophic open Atlantic Ocean bacterioplankton with leucine, or other molecules indicative of microbial metabolism, leads to the measurement of a response to a nutrient addition, rather than an ambient measurement.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Low microbial respiration of leucine at ambient oceanic concentration in the mixed layer of the central Atlantic Ocean

Hill

Warwick

Zubkov

2013

Limnology & Oceanography

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“…The GB MGI genomes contain 57 predicted ABCtype transporters for uptake of amino acids, which might be an important source of carbon, nitrogen and energy for marine heterotrophs, including MGI (Fuhrman, 1987;Suttle et al, 1991;Ouverney and Fuhrman, 2000). Although this indicates genomic potential for heterotrophy in the GB MGI, these transporters recruited few or no transcripts (p2), suggesting that transcription of genes encoding MGI amino acid transporters was lower than those for carbon fixation.…”

Section: Species-resolved Transcriptomics Of Ammonia Oxidation Genesmentioning

confidence: 99%

Genome-enabled transcriptomics reveals archaeal populations that drive nitrification in a deep-sea hydrothermal plume

2012

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Ammonia-oxidizing Archaea (AOA) are among the most abundant microorganisms in the oceans and have crucial roles in biogeochemical cycling of nitrogen and carbon. To better understand AOA inhabiting the deep sea, we obtained community genomic and transcriptomic data from ammonium-rich hydrothermal plumes in the Guaymas Basin (GB) and from surrounding deep waters of the Gulf of California. Among the most abundant and active lineages in the sequence data were marine group I (MGI) Archaea related to the cultured autotrophic ammonia-oxidizer, Nitrosopumilus maritimus. Assembly of MGI genomic fragments yielded 2.9 Mb of sequence containing seven 16S rRNA genes (95.4–98.4% similar to N. maritimus), including two near-complete genomes and several lower-abundance variants. Equal copy numbers of MGI 16S rRNA genes and ammonia monooxygenase genes and transcription of ammonia oxidation genes indicates that all of these genotypes actively oxidize ammonia. De novo genomic assembly revealed the functional potential of MGI populations and enhanced interpretation of metatranscriptomic data. Physiological distinction from N. maritimus is evident in the transcription of novel genes, including genes for urea utilization, suggesting an alternative source of ammonia. We were also able to determine which genotypes are most active in the plume. Transcripts involved in nitrification were more prominent in the plume and were among the most abundant transcripts in the community. These unique data sets reveal populations of deep-sea AOA thriving in the ammonium-rich GB that are related to surface types, but with key genomic and physiological differences.

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Resource Control of Bacterial Dynamics in the Sea

Church

2008

Microbial Ecology of the Oceans

116

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Dissolved free amino acids in the Sargasso Sea: uptake and respiration rates, turnover times, and concentrations

Cited by 114 publications

References 33 publications

Low microbial respiration of leucine at ambient oceanic concentration in the mixed layer of the central Atlantic Ocean

Low microbial respiration of leucine at ambient oceanic concentration in the mixed layer of the central Atlantic Ocean

Genome-enabled transcriptomics reveals archaeal populations that drive nitrification in a deep-sea hydrothermal plume

Resource Control of Bacterial Dynamics in the Sea

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