SUGAR-CONTAINING COMPOUNDS ON THE CELL SURFACES OF MARINE DIATOMS MEASURED USING CONCANAVALIN A AND FLOW CYTOMETRY |
| |
Authors: | Anya M. Waite Robert J. Olson Hans G. Dam Uta Passow |
| |
Affiliation: | Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543;Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340;Marine Sciences Institute, University of California Santa Barbara, Santa Barbara, California 93106 |
| |
Abstract: | Some diatom exudates may remain attached to the exterior cell surface, potentially altering cell stickiness and affecting important aspects of the diatom's ecology such as aggregation rates and grazing rates. We measured the accumulation of cell-surface sugar-containing compounds by labeling cultured marine diatoms with fluorescent-tagged sugar-binding lectins and measuring the fluorescence associated with each cell using flow cytometry. The binding of FITC-labeled concanavalin A (FITC-ConA), a lectin that binds to glucose and mannose residues, varied 5-fold among different diatom species in exponential growth (on a per-cell basis) and 2–3-fold within a given species in different physiological states. Although transparent exopolymer particles followed a simple accumulation curve over time in batch culture, FITC-ConA. cell-1 did not follow the same pattern, suggesting that surface sugar accumulation is not driven simply by the accumulation of such particles in the medium. For Thalassiosira pseudonana (Hustedt) Hasle and Heimdal (3H clone), the amount of sugar-containing compounds on the cell surface increased transiently as growth rate slowed in early stationary phase under both N and Si limitation. For Chaetoceros neogracile (Schuett) van Landingham, FITC-ConA. cell-1had a strong inverse relationship with growth rate across several Si-limited batch culture experiments. Both results suggest some biological mediation of cell-surface sugar-containing compounds. Our study reveals the great potential for using lectin binding to investigate cell-surface sugars on diatoms. Lectins allow us to investigate noninvasively the role of cell-surface sugar-containing compounds in modifying cell stickiness and aggregation, as well as the partitioning of exuded phytoplankton carbon. We suggest that cell-surface sugar accumulation may be related to diatom stickiness, based on a correlation between our FITC-ConA measurements and stickiness estimates in the literature on several of the species we studied. |
| |
Keywords: | Bacillariophyceae cell surfaces Chaetoceros neogracile concanavalin A FITC-labeled ConA flow cytometry lectins sugar-containing compounds Thalassiosira pseudonana |
|
|