Details zur Publikation

Kategorie Textpublikation
Referenztyp Zeitschriften
DOI 10.1111/j.1529-8817.2009.00707.x
Titel (primär) Mixotrophic algae constrain the loss of organic carbon by exudation
Autor Kamjunke, N.; Tittel, J.
Quelle Journal of Phycology
Erscheinungsjahr 2009
Department SEEFO
Band/Volume 45
Heft 4
Seite von 807
Seite bis 811
Sprache englisch
Keywords Algae; bacteria; chemostat; competition; DOC; exudation; mixotroph
Abstract Algae of various taxonomic groups are capable of assimilating dissolved organic carbon (DOC) from their environments (mixotrophy). Recently, we reported that, with increasing biomass of mixotrophs, heterotrophic bacteria did not increase. We hypothesized that algal uptake of external DOC may outweigh their release of DOC by exudation (H1). Here, we addressed an alternative hypothesis that algae did not assimilate external DOC but constrained the release of DOC (H2). In chemostat experiments, we cultured the mixotrophic Chlamydomonas acidophila Negoro together with heterotrophic bacteria. As external substrates, we used glucose, which was potentially available for both bacteria and algae, or fructose, which was available only for bacteria. We increased the biomass of algae by the stepwise addition of phosphorus. Bacterial biomass did not increase in experiments using glucose or when fructose was offered, suggesting that mechanisms other than algal mixotrophy (H1) kept concentrations of bacteria low. Measured exudation rates (percent extracellular release, PER) of mixotrophic algae (Cd. acidophila, Chlorella protothecoides W. Krüger) were very low and ranged between 1.0% and 3.5% at low and moderately high phosphorus concentrations. In contrast, an obligately phototrophic alga (Chlamydomonas segnis H. Ettl) showed higher exudation rates, particularly under phosphorus limitation (70%). The results support H2. If mixotrophy is considered as a mechanism to recycle organic exudates from near the cell surface, this would explain why algae retained mixotrophic capabilities although they cannot compete with bacteria for external organic carbon.
dauerhafte UFZ-Verlinkung
Kamjunke, N., Tittel, J. (2009):
Mixotrophic algae constrain the loss of organic carbon by exudation
J. Phycol. 45 (4), 807 - 811 10.1111/j.1529-8817.2009.00707.x