M17 agar

This bacterial growth medium was developed in 1971 for Lactococcus species isolated from milk products. It was originally called M16 medium,^[1] but in 1975 Terzaghi and Sandine^[2] added disodium-β-glycerophosphate to the medium as a buffer, and named the new growth medium M17 medium. It was later found that the addition of disodium-β-glycerophosphate inhibits the growth of many Lactobacillus species.^[3]

Per 950 mL:^[2]

• 5.0 g Pancreatic digest of casein
• 5.0 g Soy Peptone
• 5.0 g Beef extract
• 2.5 g Yeast extract
• 0.5 g Ascorbic acid
• 0.25 g Magnesium sulfate
• 19.0 g Disodium-β-glycerophosphate
• 11.0 g Agar

Preparation:

• 1. Heat with frequent agitation and boil for 1 minute to completely dissolve.
• 2. Autoclave at 121 °C for 15 minutes. Cool to 50 °C.
• 3. Add 50 ml filter sterilized 10% lactose solution and mix well (the lactose can be exchanged to other carbohydrates e.g. glucose, resulting in GM17 medium)