Lactobacillus bulgaricus was a bacteria originally found in and on plants. While it is not known exactley how L. bulgaricus made the jump from plants to dairy, it is accepted that the bacteria did in fact mutate and adapt to growing in milk, and is still mutating, some believe rapidly. The bacteria found yogurt to be a safe, fairly constant environment, and because Streptococcus thermophilus also exists in yogurt, it has lost some functions that S. thermophilus has.

Lactobacillus bulgaricus was named after the country Bulgaria, since Stamen Grigorov, the scientist who discovered it, was Bulgarian. Dr. Grigorov discovered L. bulgaricus at the age of twenty-seven. He purportedly made this discovery while examining yogurt. This was Dr. Grigorov's most famous discovery. He discovered L. bulgaricus in 1905.

While some species of Lactobacillus are used for fermenting vegetables, L. bulgaricus is not one of them, even though it was originally found on plants.

For a comprhensive report on the geneology of L. bulgaricus, click here.