Changes in Morphology and Elemental Composition of Vibrio splendidus Along a Gradient from Carbon-limited to Phosphate-limited Growth
We examined morphology, elemental composition (C, N, P), and orthophosphate-uptake efficiency in the marine heterotrophic bacterium Vibrio splendidus grown in continuous cultures. Eight chemostats were arranged along a gradient of increasing glucose concentrations in the reservoirs, shifting the limiting factor from glucose to phosphate. The content of carbon, nitrogen, and phosphorus was measured in individual cells by x-ray microanalysis using a transmission electron microscope (TEM). Cell volumes (V) were estimated from length and width measurements of unfixed, air-dried cells in TEM. There was a transition from coccoid cells in C-limited cultures toward rod-shaped cells in P-limited cultures. Cells in P-limited cultures with free glucose in the media were significantly larger than cells in glucose-depleted cultures (P < 0.0001). We found functional allometry between cellular C-, N-, and P content (in femtograms) and V (in cubic micrometers) in V. splendidus (C = 224 × V 0.89, N = 52.5 × V 0.80, P = 2 × V 0.65); i.e., larger bacteria had less elemental C, N, and P per V than smaller cells, and also less P relative to C. Biomass-specific affinity for orthophosphate uptake in large P-limited V. splendidus approached theoretical maxima predicted for uptake limited by molecular diffusion toward the cells. Comparing these theoretical values to respective values for the smaller, coccoid, C-limited V. splendidus indicated, contrary to the traditional view, that large size did not represent a trade-off when competing for the non-C-limiting nutrients.
KeywordsVibrio Soluble Reactive Phosphorus Free Glucose Cell Quota Late Logarithmic Phase
This work was supported by the Strategic Institution Programme “Patterns in Biodiversity” Contract 158936/S40 from the Research Council of Norway. The FACSCalibur flow cytometer was in part funded by a grant from The Knut and Alice Wallenberg Foundation to the Virtue program. We gratefully thank Philippe Lebaron for providing the V. splendidus culture, Tsuneo Tanaka for advice and assistance, George Jackson for providing information on diffusion literature, and Egil S. Erichsen for his assistance at the Laboratory for Electron Microscopy (LEM), Science Faculty, University of Bergen.
- 2.Clift, R, Grace, JR, Weber, ME (1978) Bubbles, drops, and particles. Academic Press, New YorkGoogle Scholar
- 3.Currie, DJ, Kalff, J (1984) A comparison of the abilities of freshwater algae and bacteria to acquire and retain phosphorus. Limnol Oceanogr 29: 298–310Google Scholar
- 6.Flaten, GAF (2004) Phosphate limitation in marine osmotrophs: affinity and competition. DSc thesis, University of Bergen, BergenGoogle Scholar
- 7.Goldman, JC, Caron, DA, Dennet, MR (1987) Regulation of gross growth efficiency and ammonium regeneration in bacteria by substrate C:N ratio. Limnol Oceanogr 32: 1239–1252Google Scholar
- 9.Jumars, PA (1993) Concepts in biological oceanography: an interdisciplinary primer. Oxford University Press, OxfordGoogle Scholar
- 10.Jumars, PA, Deming, JW, Hill, PS, Karp-Boss, L, Yager, PL, Dade, WB (1993) Physical constraints on marine osmotrophy in an optimal foraging context. Mar Microb Food Webs 7: 121–159Google Scholar
- 11.Karp-Boss, L, Boss, E, Jumars, PA (1996) Nutrient fluxes to planktonic osmotrophs in the presence of fluid motion. Oceanogr Mar Biol Ann Rev 34: 71–107Google Scholar
- 14.Koroleff, F (1983) Determination of phosphorus. In: Grasshoff, K, Erhardt, M and Kremling, K (Eds.) Methods in seawater analysis. Verlag Chemie, pp 125–131Google Scholar
- 21.Morita, RY (1982) Starvation-survival of heterotrophs in the marine environment. Adv Microb Ecol 6: 171–198Google Scholar
- 33.Sokal, RR, Rohlf, FJ (1995) Biometry, 3rd ed. W.H. Freeman, New YorkGoogle Scholar
- 34.Sterner, RW, Elser, JJ (2002) Ecological stoichiometry. The biology of elements from molecules to the biosphere. Princeton University Press, Princeton, NJGoogle Scholar