Microbiology: Media recipes

*It is usually better to buy ready-made microbiology media, but some microbes call for special diets.*

The following recipes may prove useful, although in most cases we suggest that pre-mixed media are purchased (Fisher Scientific supply Oxoid products at reasonable prices).

GLUCOSE NUTRIENT AGAR

Oxoid CM0003 Nutrient agar, 28 g
Glucose, 10 g

Make up to 1 litre with demineralised or distilled water. Autoclave at 121 °C for 15 minutes. Note: this medium has only 1% glucose in it, and therefore it is possible to autoclave all of the ingredients together without the risk of unwanted Maillard (‘browning’) reactions.

GLUCOSE NUTRIENT BROTH

Oxoid CM0001 Nutrient broth, 13 g
Glucose, 10 g

SALINE NUTRIENT BROTH
(FOR VIBRIO NATRIGENS GROWTH EXPERIMENTS)

Nutrient broth, 13 g
NaCl, 20g

Make up to 1 litre with demineralised or distilled water. Autoclave at 121 °C for 15 minutes. After autoclaving, adjust the pH to 7.5. Note: Saline Heart-Brain infusion broth is often used to promote the rapid growth of Vibrio natrigens, so that growth curves can be produced in a very short time, but the medium is costly. This inexpensive alternative will allow a growth curve to be produced in 2–3 hours if the culture is incubated at 30 °C.

TRIBUTYRIN NUTRIENT AGAR
(FOR THE DETECTION OF LIPASE ACTIVITY)

Oxoid CM0003 Nutrient agar, 28 g
Glycerol tributyrate, 10 mL

Make up to 1 litre with demineralised or distilled water. Autoclave at 121 °C for 20 minutes. After autoclaving, adjust the pH to 7.2.

STARCH AGAR
(FOR THE DETECTION OF AMYLASE ACTIVITY)

NaNO₃, 3 g
KCl, 0.5 g
MgSO₄.7H₂O, 0.5 g
Na₂HPO₄.12H₂O, 1 g
FeSO₄.7H₂O, 0.01 g
Agar, 15 g

Dissolve the above in 900 mL of distilled water. Dissolve 2 g of starch in 100 mL of hot water. Add to the mineral solution. Autoclave and dispense as usual.

CMC AGAR (FOR GROWING CELLULOMONAS)

CMC medium contains the following:

Carboxymethylcellulose, 5 g
NaNO_{3, 1 g}
K₂HPO_{4, 1 g}
KCl, 1 g
MgSO₄.7H₂O, 0.5 g
Yeast extract, 0.5 g
Glucose, 1 g
Agar, 15 g