A Lab Notebook

 
Ki%F8rboe & Hansen [1993]
Kiørboe and Hansen [1993] did not find any relationship between the age (growth phase) of batch cultures and cell stickiness (5 diatoms and 2 dinoflagellates). Their method of stickiness prameterization utilized a traditional couette device with shear rates near 10/s. They observed S. costatum to have an alpha between 0.036 and 0.049.5. They observed 2 types of sticking; cell-cell (as in S. costatum) and TEP-cell (as in C. affinis). S. costatum also produced an exudate that reduced the apparent stickiness of the culture. They also cleaned S. costatum cells by washig three times by centrifugation and resuspension in filtered seawater. Centrifugation did not have an affect on the cells. T. weissflogii was was not sticky and did not form aggregates in their cultures. This is the resaon I chose T. weissflogii as my non-sticky algal cell in my first flume experiment. Coscinodiscus is a profligate mucus producer.
They also note from this paper and an earlier paper, the apparent relationship between cell concentration and stickiness. This relationship may indicate some sort of repulsive solute or a stickiness inhibitor released by cells at high concentrations. However, they tested for a stickiness inhibtor and could not find strong evidence of the presence of such an exudate.
Additonally, the hypothesis of two different exudates released by plankton is explored. Based on Dechos 1990 review, a capsular mucus is released during exponential growth of diatoms while a colloidal or more loosely bound (to the cell) mucus is released by diatoms during the stationary phase. Kiørboe and Hansen further hypothesized that only the capsular mucus (the one stained by alcian blue - side note: Alcian Blue staining is specific to mucopolysaccharides with carboxyl groups) causes cell-cell aggregation. However the loose exudates may be responsible for flocculation beyond the interaction of cells.
- posted by alex @ 17:55