Lactobacillus bulgaricus is a gram-positive rod that may appear long and filamentous. It is non-motile and does not form spores. It is also non-pathogenic. It is regarded as aciduric or acidophilic, since it requires a low pH (around 5.4–4.6) to grow effectively. In addition, it is anaerobic. As it grows on raw dairy products, it creates and maintains the acidic environment that it needs to thrive via its production of lactic acid. In addition, it grows optimally at temperatures of 40-44 °C under anaerobic conditions. It has complex nutritional requirements which vary according to the environment. These include carbohydrates, unsaturated fatty acids, amino acids, and vitamins.