← Back
B. Media for marine and brackish-water cyanobacteria
MNMN (BG-11 on seawater)
Hybrid medium: BG-11 nutrients + natural seawater
- Application
- Marine Synechococcus, benthic marine cyanobacteria; the basis for PRO99 medium (Prochlorococcus)
- pH
- 7.8–8.2
- Source
- Rippka et al., 1979; Waterbury et al., 1986
Composition
| Component | Amount per 1 L |
|---|---|
| Seawater (filtered) | 750 mL |
| Distilled water | 250 mL |
| NaNO₃ | 0.75 g |
| K₂HPO₄·3H₂O | 0.02 g |
| Citric acid | 3 mg |
| Ferric ammonium citrate | 3 mg |
| Na₂EDTA | 0.5 mg |
| Na₂CO₃ | 0.02 g |
| A5 + Co trace element solution | 1.0 mL |
A5 + Co trace element solution
per 100 mL of solution · usage rate 1 mL per 1 L of medium (sufficient for 100 L) · storage at 4 °C in dark glass, 12 months
| Component | Weighed amount / volume |
|---|---|
| H₃BO₃ | 286 mg |
| MnCl₂·4H₂O | 181 mg |
| ZnSO₄·7H₂O | 22.2 mg |
| Na₂MoO₄·2H₂O | 39.0 mg |
| CuSO₄·5H₂O | 7.9 mg |
| Co(NO₃)₂·6H₂O | 4.94 mg (or 1 mL of a primary stock solution at 4.94 g/L) |
| Distilled water | to 100 mL |
Preparation
Filter the seawater (0.45 → 0.22 µm), mix it with the distilled water and autoclave SEPARATELY. Prepare the nutrients (nitrate, phosphate, citrates, EDTA, carbonate, A5) as a concentrate in 50 mL, sterilise by filtration and add aseptically to the cooled seawater.
Notes
- Before use the seawater is held in the dark for 2–4 weeks ("ageing") to mineralise dissolved organic matter, and is then filtered.
- Autoclaving seawater together with phosphate produces a copious precipitate of calcium and magnesium phosphates — separate sterilisation is mandatory.
- Dilution to 75 % (≈ 26 ‰) corresponds to coastal-water conditions; for oceanic strains undiluted seawater is used.
- Dissolve the salts one at a time, in the order given; H₃BO₃ dissolves slowly — warming to 40 °C is permissible. Cobalt is added from a primary stock solution: a weighed amount of 4.94 mg cannot be measured on an ordinary balance. Primary Co stock solution: 494 mg Co(NO₃)₂·6H₂O in 100 mL of water, take 1 mL. Without cobalt the solution is simply called "A5". The appearance of a precipitate or turbidity indicates that the solution is no longer usable.