Article Figures & Data
Figures
- FIG 1
Photosynthesis and cellular carbon and energy stores in Prochlorococcus strain VOL29. Comparisons of the temporal effects (at 12:00 and 16:00, left and right, respectively) and nitrogen availability (limiting and replete; orange and blue, respectively) on total carbon fixation rates (A), the fraction of fixed carbon that is associated observed in the particulate (>0.2 μm) (B), and cellular carbon and energy stores determined through measurements of total polysaccharides (C). *, P < 0.05 by Welch’s t test.
- FIG 2
Central carbon metabolism in N-limited and -replete VOL29 cultures at 12:00. Comparisons of per cell normalized metabolite pools between nitrogen-limited and -replete cultures of VOL29 (see Table S1 in the supplemental material). Bar graphs reflect means from biological replicates. Specific enzymes addressed in discussion are fructose-1,6-bisphosphatase II/sedoheptulose-1,7-bisphosphatase (GlpX; 1), transketolase (TktA; 2), and phosphoribokinase (Prk; 3). 1,3BPG, 1,3-bisphosphoglycerate; 3PG, 3-phosphoglycerate; E4P, erythrose 4-phosphate; F6P, fructose 6-phosphate; FBP, fructose 1,6-bisphosphate; G3P, phosphoglyceraldehyde; Glu-1-P, glucose 1-phosphate; Glu-6-P, glucose 6-phosphate; R5P, ribose 5-phosphate; Ru5P, ribulose 5-phosphate; S7P, sedoheptulose 7-phosphate; SBP, sedoheptulose 1,7-bisphosphate; X5P, xylulose 5-phosphate.
- FIG 3
Carbon flux analysis of VOL29 N-limited and -replete cultures. Carbon flux through metabolite pools displayed through two isotopic enrichment analysis methods: fractional contribution (FC) (A) and mass distribution vector (MDV) (B). Isotopic carbon labeling of metabolite isotopologues (M + i) is displayed as MDV, where M represents unlabeled isotopologues and i is the number of isotopically labeled atoms in the carbon backbone of the metabolite. Error bars for FC represent standard deviations. MDV data represent averages from technical replicates (n = 3) for each biological replicate over 90 min. See Table S2 for IC values.
- FIG 4
Nitrogen metabolism in N-limited and -replete VOL29 cultures at 12:00. Comparisons of per cell normalized metabolite pools between nitrogen-limited and -replete cultures of VOL29 (Table S1). Metabolites in red font contain nitrogen. Specific enzymes addressed in Discussion are glutamine synthetase (GS; 1), glutamine-oxoglutarate amido transferase (GOGAT; 2), N-acetyl-glutamate kinase (NAGK; 3), and phosphoenolpyruvate carboxylase (PEPc; 4). 1,3BPG, 1,3-bisphosphoglycerate; 2PG, 2-phosphoglycerate; 2OG, 2-oxoglutarate; 3PG, 3-phosphoglycerate; G3P, phosphoglyceraldehyde; OAA, oxaloacetate; PEP, phosphoenolpyruvate; PYR, pyruvate.
- FIG 5
Glutamate flux in natural populations of Prochlorococcus in the North Pacific Ocean. Over a series of two research cruises, six experiments measuring carbon flux through metabolites in Prochlorococcus-enriched microcosms were measured. Comparisons of FC analysis of cruise data (grayscale lines) and the laboratory nitrogen limited and nutrient replete (orange and blue lines, respectively). Sea surface temperatures for each station are noted in the legend, and measurements of ammonium concentrations are noted at the end of the line that they describe (Table S3).
Supplemental Material
TABLE S1
Nitrogen limited and nitrogen replete metabolite pool data. Metabolite abundance measured as the total ion counts normalized to cells per milliliter for both nitrogen (N)-limited and -replete cultures. Metabolites with observed isotopic labeling denoted with asterisks. Download Table S1, DOCX file, 0.02 MB.
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TABLE S2
Nitrogen limited and nitrogen replete metabolite 13C labeling. Raw isotopologue abundance (integrated ion counts) for 13C-labeled metabolites in nitrogen-limited and -replete cultures at both noon (12:00) and afternoon (16:00) time points. Isotopologues are described in their unlabeled and labeled forms, where “metabolite + i” is the number of isotopic carbons in that isotopologue. Abbreviations: Glu, glutamate; HexP, hexose phosphate; Asp, aspartate; S7P, sedoheptulose 1/7-phosphate; UDP-Glc, UDP-glucose; UDP-GlcN, UDP-N-acetyl-glucosamine. Download Table S2, DOCX file, 0.03 MB.
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TABLE S3
Experimental station details. Experiments and sampling occurred over two similar cruise tracks separated by approximately 6 months in the North Pacific Ocean. Cell counts performed on whole water samples prior to size fractionation. Download Table S3, DOCX file, 0.01 MB.
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FIG S1
N-limited and N-replete cultures prior to and following experiments. Comparisons of VOL29 growth under nitrogen-limited (Nlim; orange) and -replete (Nrep; blue) growth conditions leading up to and following destructive sampling of chemostats on the day of the experiment (day 0; dotted vertical line). After day 0, nitrogen amendment experiments (day 1 to 10) were performed in batch culture (+N) and compared to unamended controls (Cntrl). Mean per cell fluorescence, as determined by the average fluorescence of events counted by flow cytometry, allows for the comparison of the average chlorophyll content per cell. Error bars represent standard deviations. Download FIG S1, JPG file, 0.5 MB.
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FIG S2
Light intensity of sunbox incubator. Light levels designed to mimic pattern of natural sunlight shown as white on black background. Artificial sunrise occurred at 04:00 and sunset at 18:00. Experimental time points began at 12:00 and 16:00. Download FIG S2, JPG file, 0.3 MB.
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FIG S3
Comparison of VOL29 growth in current and trial grow-out experiments. Under identical growth conditions to our current study (red lines), VOL29 cultures grown in N-limited chemostats were observed to stabilize around 4.5 × 107 cells · ml−1 over a 15-day grow-out experiment (black lines), suggesting that growth rates for the conditions tested are approximately balanced to the dilution rate of the chemostat (∼0.09 day−1). The 7-day period shown for the current study correspond to days −6 through 0 for Fig. 1. Download FIG S3, JPG file, 0.6 MB.
Copyright © 2019 Szul et al.
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