ASM-1

ASM-1 trace element solution — working solution

per 100 mL · usage rate 1 mL per 1 L of medium · storage at 4 °C, 6 months

Primary stock solutions for ASM-1 (prepared separately)

each per 100 mL · 1 mL of each is taken · storage at 4 °C, 6 months

Dissolve NaNO₃ → MgSO₄·7H₂O → MgCl₂·6H₂O → both phosphates → 1 mL of the trace element solution → CaCl₂·2H₂O last → make up to 1000 mL → pH 6.8–7.0.

• ASM-1 is deliberately poorer in nitrogen and phosphorus than BG-11 (2.0 mM N against 17.6 mM) — this makes it convenient for studying nutrient limitation and toxin production in Microcystis.
• The dual phosphate system (K₂HPO₄ + Na₂HPO₄·12H₂O) acts as a weak buffer; under intense photosynthesis its capacity is insufficient and the pH rises above 9 — air sparging is then required.
• Na₂EDTA is dissolved first and FeCl₃ after it. Cobalt and copper are added only from primary stock solutions: the weighed amounts per 100 mL would be 1.9 mg and 0.04 mg respectively.
• The copper solution is extremely dilute: 4 mg per 100 mL. If the balance cannot weigh such a small amount, prepare a solution of 0.4 g per 100 mL and dilute it 100-fold.