Magnesium sulfate
The yeast/meat extracts and peptone provide sources of carbon, nitrogen, and vitamins for general bacterial growth. The yeast extract also contains vitamins and amino acids specifically required by "Lactobacilli". Polysorbate 80 is a surfactant which assists in nutrient uptake by "Lactobacilli". Magnesium sulfate and manganese sulfate provide cations used in metabolism.