MEPS 250:81-89 (2003)  -  doi:10.3354/meps250081

Characterization of extracellular polymers of Phaeocystis globosa and P. antarctica

Caroline M. Solomon1,2,*, Evelyn J. Lessard1, Richard G. Keil1, Michael S. Foy1

1School of Oceanography, University of Washington, Box 357940, Seattle, Washington 98195, USA
2Gallaudet University, Department of Biology, 800 Florida Avenue, NE, Washington, DC 20002, USA

ABSTRACT: Extracellular polymers of Phaeocystis globosa and P. antarctica were characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), and matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis. The 2 species were grown in axenic and bacterized cultures to examine the effect of bacterial degradation on the composition of the extracellular polymers. The C:N ratios for extracellular polymers from P. globosa and P. antarctica grown under these conditions were lower (<9) than in previous reports (>12). P. antarctica polymer C:N was significantly lower than that of P. globosa. Contrary to expectations, the polymer C:N from bacterized cultures was slightly lower than from axenic cultures. XPS analysis indicated that the polymers are carbohydrate-rich, and MALDI-TOF-MS analysis showed that the nitrogen was not proteinaceous, but probably originated from low molecular weight compounds such as amino sugars. The low C:N ratios suggest that extracellular polymers may directly provide a substrate for bacteria and heterotrophic protists without the need for other sources of nitrogen.

KEY WORDS: Phaeocystis spp. · Carbohydrates · C:N ratio · Extracellular polymers

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