Blue-Green (BG) Medium

This medium is made up in 2 parts. Autoclave Parts 1 and 2 separately at 15 psi, allow to cool then mix aseptically. For agar plates, add 15 g non-nutrient agar per L.

Tricine 0.50 g
Soil extract (SE1) 25.00 ml
Extra nutrient salts 3.75 ml
Filtered natural seawater to 1.0 L

Adjust pH to 7.6 - 7.8 with 1M NaOH or HCl.

NaNO3 1.500 g
K2HPO4 3H2O 0.040 g
MgSO4 7H2O 0.075 g
CaCl2 2H2O 0.036 g
Citric acid 0.006 g
Ammonium ferric citrate green 0.006 g
EDTANa2 0.001 g
Na2CO3 0.020 g
Trace metal solution 1.00 ml
Distilled water to 1.0 L

Adjust pH to 7.4.

Extra nutrient salts:
NaNO3 3.00 g
Na2HPO4 0.12 g
K2HPO4 0.10 g
Distilled water to 100.0 ml

Trace metal solution:
H3BO3 0.286 g
MnCl2 4H2O 0.022 g
Na2MoO4 2H2O 0.039 g
CuSO4 5H2O 0.008 g
Co(NO3)2 6H2O 0.005 g
Distilled water to 100.0 ml

Soil Extract (SE1):
Site selection for a good soil is very important and for most purposes a soil from undisturbed deciduous woodland is best. Sites to avoid are those showing obvious signs of man's activity and particular care should be taken to avoid areas where fertilizers, crop sprays or other toxic chemicals may have been used.

A rich loam with good crumb structure should be sought. Stones, roots and larger invertebrates should be removed during an initial sieving through a 1 cm mesh. The sieved soil should be spread to air dry and hand picked for smaller invertebrates and roots. It should be turned periodically and picked over again. When dry it may be sieved through a finer mesh (2-4 mm) or stored as it is prior to use.

Air-dried soil and twice its volume of supernatant distilled water are autoclaved together at 15 psi for 2 hours and left to cool. The supernatant is then decanted and filtered through Whatman No. 1 filter paper, then distributed to containers in volumes suitable for making up batches of media. The aliquots and their containers are autoclaved for an appropriate length of time (eg., 1 L or less for 15 minutes) and are then kept in a cool place (eg., a refrigerator) until required.

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