M17 broth is based on the formulation described by Terzaghi and Sandine (1) for the cultivation and enumeration of lactic Streptococci and their bacteriophages. M17 Broth is a modification of M16 Medium (2).
Lactic Streptococci are nutritionally fastidious and require complex media for optimal growth (3, 4). Disodium glycerophosphate maintains the pH above 5.7. The maintenance of pH is very important as the lower pH results in injury and reduced recovery of lactic Streptococci. Glycerophosphate does not form precipitate with calcium which is needed for the plaque assay of lactic bacteriophages.
Peptic digest of animal tissue, casein enzymix hydrolysate, papaic digest of soyabean meal, yeast extract, beef extract, provide carbonaceous, nitrogenous compounds, vitamin B complex and other essential growth factors. Lactose is the fermentable carbohydrate and ascorbic acid is stimulatory for the growth of lactic Streptococci. Magnesium sulphate provides essential ions to the organisms.
Disodium-#-glycerophosphate maintains the pH above 5.7. The maintenance of pH is very important as lower pH results in injury and reduced recovery of lactic Streptococci. Shankar and Davies (5) reported isolation and enumeration of Streptococcus thermophilus from yoghurt. Disodium glycerophosphate suppresses Lactobacillus bulgaricus.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
References:
1. Terzaghi B.E. and Sandine W.E., 1975, Appl. Microbiol., 29:807.
2. Lawrie and Pearee, 1971, J. Dairy Sci. Technol., 6:166.
3. Anderson A.W. and Elliker P.R., 1953, J. Dairy Sci., 36:161.
4. Reiter B. and Oran J.D., 1962, J. Dairy Res., 29:63.
5. Shankar P.A. and Davies F.L., 1977, Soc. Dairy Technol., 30:28.