Lactobacillus bulgaricus, the bacterium that gives Bulgarian yoghurt its unique flavour and thickness, can be found only in Bulgaria. Yoghurt may seem like something new because of its current popularity but it has been around for centuries. Basically, all yoghurt is cultured milk. The bacteria used most commonly are Lactobacillus bulgaricus (named so because yogurt was first discovered by the people of Bulgaria) and Streptococcus thermophilus. This is what gives yoghurt its jelly-like texture and semisour, tangy taste.