Lactobacillus delbrueckii subsp. bulgaricus

Lactobacillus delbrueckii subsp. bulgaricus
Lactobacillus delbrueckii subsp. bulgaricus from a sample of yogurt. Numbered ticks are 11 μm apart.
Scientific classification
Domain:	Bacteria
Phylum:	Bacillota
Class:	Bacilli
Order:	Lactobacillales
Family:	Lactobacillaceae
Genus:	Lactobacillus
Species:	L. delbrueckii
Subspecies:	L. d. subsp. bulgaricus
Trinomial name
Lactobacillus delbrueckii subsp. bulgaricus (Orla-Jensen 1919) Rogosa & Hansen 1971 Weiss et al. 1984
Synonyms[2]
"Bacillus bulgaricus" Grigorov 1905[1] "Thermobacterium bulgaricum" Orla-Jensen 1919 Lactobacillus bulgaricus (Orla-Jensen 1919) Rogosa & Hansen 1971 (Approved Lists 1980)

Lactobacillus delbrueckii subsp. bulgaricus is the main bacterium used for the production of yogurt. It also plays a crucial role in the ripening of some cheeses,^[3] as well as in other processes involving naturally fermented products. It is defined as homofermentive lactic acid bacteria due to lactic acid being the single end product of its carbohydrate digestion. It is also considered a probiotic.^[4]

It 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.^[5] 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.

First identified in 1905 by the Bulgarian doctor Stamen Grigorov by isolating what later termed Lactobacillus delbrueckii subsp. bulgaricus from a Bulgarian yogurt sample,^[6] the bacteria can be found naturally in the gastrointestinal tract of mammals living in Shopluk mesoregion of Balkan peninsula.^{[citation needed]} One strain, Lactobacillus bulgaricus GLB44, is extracted from the leaves of the Galanthus nivalis (snowdrop flower) in Bulgaria.^[7] The bacterium is also grown artificially in many countries.