Citation:

journal.pone.0121675

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Abstract:

Marine planktonic bacteria often live in habitats with extremely low concentrations of dissolved organic matter (DOM). To study the use of trace amounts of DOM by the facultatively oligotrophic Pseudovibrio sp. FO-BEG1, we investigated the composition of artificial and natural seawater before and after growth. We determined the concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), free and hydrolysable amino acids, and the molecular composition of DOM by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). The DOC concentration of the artificial seawater we used for cultivation was 4.4 µmol C/l, which was eight times lower compared to the natural oligotrophic seawater we used for parallel experiments (36 µmol C/l). During the three-week duration of the experiment, cell numbers increased from 40 cells/ml to 2x10**4 cells/ml in artificial and to 3x10**5 cells/ml in natural seawater. No nitrogen fixation and minor CO2 fixation (< 1% of cellular carbon) was observed. Our data show that in both media, amino acids were not the main substrate for growth. Instead, FT-ICR-MS analysis revealed usage of a variety of different dissolved organic molecules, belonging to a wide range of chemical compound groups, also containing nitrogen. The present study shows that marine heterotrophic bacteria are able to proliferate with even lower DOC concentrations than available in natural ultra-oligotrophic seawater, using unexpected organic compounds to fuel their energy, carbon and nitrogen requirements.

Project(s):

Elemental nitrogen oxidation A new bacterial process in the nitrogen cycle (ELNOX)

Funding:

Seventh Framework Programme (FP7), grant/award no. 203364 : Elemental nitrogen oxidation A new bacterial process in the nitrogen cycle

Event(s):

Pseudovibrio_ASW_EXP * Method/Device: Experiment (EXP) * Comment: Artificial oligotrophic seawater medium was made in the laboratory, see Schwedt et at., 2015.

Pseudovibrio_SW_EXP * Method/Device: Experiment (EXP) * Comment: Natural surface seawater was collected with a bucket in the South Pacific during IODP 329-U1368 (-27.9°N; -137.9°E).

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator	Method/Device	Comment
1	Event label	Event
2	Treatment	Treat		Schwedt, Anne
3	Mass-to-charge ratio	m/z		Schwedt, Anne
4	Molecular formula	Formula		Schwedt, Anne
5	Hydrogen/Carbon ratio	H/C		Schwedt, Anne
6	Oxygen/Carbon ratio	O/C		Schwedt, Anne
7	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 1; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
8	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 1; Replicate 1; Standard deviation between 3 replicate measurements of this timepoint
9	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 2; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
10	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 2; Standard deviation between 3 replicate measurements of this timepoint
11	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 3; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
12	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 0 at experiment start; replicate 3; Standard deviation between 3 replicate measurements of this timepoint
13	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 1; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
14	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 1; Standard deviation between 3 replicate measurements of this timepoint
15	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 2; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
16	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 2; Standard deviation between 3 replicate measurements of this timepoint
17	Peak intensity	Peak int		Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 3; Relative, normalized peak intensities, significantly changing peaks (from t0 to t2)
18	Standard deviation	Std dev	±	Schwedt, Anne	Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)	timepoint 2 after 3 weeks of incubation; replicate 3; Standard deviation between 3 replicate measurements of this timepoint

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

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9716 data points

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