This is a special chemically-defined medium without Thymine or Thymidine. Suitable for use in the cultivation of Lactobacilli from dairy products and other materials. Lactobacilli MRS Broth is based on the formulations of deMan, Rogosa and Sharpe (MRS). This medium supports luxuriant growth of Lactobacilli from oral, fecal, dairy and other sources. Animal tissue digest, beef extract and yeast extract, normally the carbon, nitrogen and vitamin sources used to satisfy general growth requirements in Lactobacilli MRS Broth, are absent and replaced with supplements and vitamins. Dextrose is the fermentable carbohydrate. Potassium acetate and ammonium citrate act as selective agents as well as energy sources. Potassium phosphate is the buffering agent. Magnesium sulfate and manganese sulfate provide cations used in metabolism. Polysorbate (Tween) 80 is a surfacant, facilitating uptake of nutrients by Lactobacilli.