Lactobacillus, also known as Döderlein’s bacillus, is a gram-positive facultative anaerobic bacteria. Gram-positive means it’s cell coating allows the absorption of a specific type of dye used to identify bacteria as gram-positive or gram-negative. Hans Gram was the guy who devised this system. Facultative means it can survive in an oxygenated or non-oxygenated environment.
Lactobacilli are the predominant strain of friendly microbe that live in most vaginas, and in much lower levels in the gut. There are some variations to vaginal populations depending on ethnicity, with black women, for example, having lower numbers of lactobacilli (and thus being more susceptible to infections like bacterial vaginosis).
They are called lacto- because they eat sugars and spit out lactic acid, which keeps the vagina acidic and healthy. Lactobacilli are little warriors, with a collection of weapons at their disposal to fight off other germs, including HIV, herpes and chlamydia. They don’t always succeed, but there would be a lot more STI infections without them.
Not all lactobacilli are created equal, with some:
- Producing hydrogen peroxide
- Producing substances called bacteriocins, that are antibacterial against other, non-lactobacilli bacteria
Lactobacilli have been associated with dental caries in the mouth, though having both a protective function against other microbes that cause carries, and being implicated in making caries worse themselves. Lactobacillus species are used in the fermentation process of foods including sourdough starter culture, water and milk kefir, yoghurt, cheese, sauerkraut, pickles, beer, wine, cider, kimchi, kombucha and cocoa, as well as silage. The lactic acid is what make foods sour-tasting.
Lactobacilli are known to have many protective effects in the human body, including anti-inflammatory, anti-cancer, anti-tumour and and anti-bacterial. Most members of this group convert lactose and other sugars to lactic acid during energy production.
There are over 180 different strains of lactobacilli, listed below. Lots of Lactobacillus use a homofermentative mechanism, which means they only produce lactic acid, instead of alcohol or lactic acid, which is how a boozy drink is made.
All known lactobacilli species
L. delbrueckii subsp. bulgaricus
L. delbrueckii subsp. delbrueckii
L. delbrueckii subsp. lactis