Monocultures of Synechococcus clone 1333 were used to examine variation and controls on Si quotas and rates of Si accumulation. The culture was procured from the National Center for Marine Algae and Microbiota (NCMA) at the Bigelow Laboratory for Ocean Sciences in Boothbay Harbor, Maine. This clone are also available in other culture collections and has various strain names. Here it is referred to by its NCMA strain number 1333 (a.k.a. CCMP number).

Cells were preconditioned in f/2 Sargasso seawater medium with 120 uM silicic acid. Inocula for experimental cultures were prepared by centrifuging and resuspending aliquots of culture into unamended surface Sargasso seawater (two centrifuge/resuspension cycles) to dilute the medium silicic acid. The carry-over of dissolved silicic acid with the cell inoculum was variable resulting in increases in [Si(OH)4] ranging from 1 - 3 uM when cells were added to experimental culture vessels. The specific centrifuging time and g-force were shown not to affect growth rate in cells relative to those added to fresh media without being concentrated (data not shown).

Cells were incubated at 21C with low light 65 microeinsteins per second per square meter (uE/m2/s) without bubbling. A 12 h light:12 h dark photocycle was used. Additions of individual components of the f/2 media were made: +NO₃, +PO₄, +vitamins & trace metals, +Si, +All constituents, and a control consisting of only aged Sargasso Sea water with triplicate measurements per treatment. Cells were incubated for an additional four hours after incubation.

Each incubation was terminated by filtration and processed for measurement of 32Si activity following Krause et al. (2011). Briefly, Synechococcus cells were filtered onto 0.2 µm polycarbonate membrane filters, the filters mounted on nylon disc planchettes, air dried, covered with mylar film and secured to the planchettes with nylon rings. After aging for 120 days, secular equilibrium between 32Si and its daughter 32P was achieved and 32Si activity was determined using gas-flow proportional counting using GM 25-5 multicounters (Risø National Laboratory, Technical University of Denmark).

Full details of culturing and experimental methods are described in Brzezinski et al. (in review). (as of 05 Jan 2017)

Culture_Media_Composition.csv