Lactobacillus – The Other Probiotic Lactic-Acid Bacteria Superstars

This page is under construction at the very end of May 2020 due to recent changes in the Lactobacillus genus. Please check back for the latest.

Lactobacillus are LAB (lactic-acid bacteria) superstar probiotics, next in line after Bifidobacterium, in my opinion. Together, both of these species of good bacteria work to help you be healthy.

Lactobacillus is the name of a genus of Gram-positive, non-sporulating, rod-shaped bacteria. The genus is classified in the phylum Firmicutes, class Bacilli, and family Lactobacillaceae, which contained up until March, 2020 the
genera Lactobacillus, Paralactobacillus, and Pediococcus genera.

Up until early 2020 this genus was comprised of 261 species that were extremely diverse at phenotypic, ecological and genotypic levels. At that time, J. Zheng et al. published a study asserting that the 261 species should be reclassified into different genera to make each genus more uniform, although they stated that the generic term ‘lactobacilli’ could still be used to indicate all organisms that were classified as Lactobacillaceae before 2020. 

As a result of that study, 261 species were whittled down to these that are commonly found in vertebrates, plus others that are not listed that are adapted to specific hosts or found in specific fermentations:

  1. L. acidophilus
  2. L. delbrueckii
  3. L. iners
  4. L. gasseri
  5. L. helveticus
  6. L. crispatus
  7. L. jensensii
  8. L. johnsonii

These good bacteria have had GRAS (generally recognized as safe) status in the US, meaning that there is general recognition of their safety through experience based on common use in foods. They also have had European QPS (Qualified Presumption of Safety) status. There should be no reason for their safety status to be revoked. Although some of the species are associated with dental caries or with infections in immune-system compromised people, most of the time they are beneficial bacteria.

For instance, some these microbes are found in everyday foods and drinks such as yogurt, kefir, cheese, and many others. So you can get the basic benefits of these bacteria just by eating some healthy fermented foods and drinks!

Kefir can contain beneficial Lactobacillus bacteria

Why Lactobacillus?

Lactobacilli (plural) are some of the most well-known probiotics. These microbes, like Bifidobacterium, are lactic-acid producing bacteria (LAB) and in fact the two genera (plural of genus) share a few common genes. This means that they take in carbohydrates and produce lactic acid. Lactobacillus prefer different kinds of carbohydrates depending on their species. Some of them can use lactose, which is nice to know if you have lactose intolerance.

Some of them also produce vitamins, short-chain fatty acids, bacteriocins (antibacterials) and antibiotic chemicals, depending on their living conditions. The benefits of their by-products are discussed in greater detail here.

Where are Lactobacilli Found?

The previous classification of lactobacilli were commonly found in the environment. As I mentioned, the smaller genus size now contains species that are more host-specific. In humans, they are found in the gastrointestinal (GI) tract, from the mouth, the nasal passages (sinuses), the throat, the esophagus, the stomach, the small intestine (the duodenum, jejunum and ileum sections) and the colon (large intestine), They are also found in the female vagina and urogenital tract.

Most, but not all, species of these bacteria are able to withstand stomach acid and bile acids and are able to attach to the mucus lining the GI tract and interact with them. Lactobacillus are the most popular genus in the last section of the small intestine, the ileum, and in the female vagina. Once established, they tend to remain life-long under normal circumstances, particularly with consistent replacement in the GI tract. Ingesting them can cause temporary increases in numbers in your body.

What Do They Do?

Some Lactobacillus species, like some Bifidobacterium species, have a beneficial effect on us just by being within us! The presence of some of these good bacteria, such as L. casei, can cause other microbes that live in the intestines to expand the helpful duties that they are capable of doing. (Similar to how some workers will increase their work output when the boss is present!)

Thus it is possible that lactobacilli communicate with other beneficial bacteria to keep us healthy.

Similar to Bifidobacterium, the total numbers of Lactobacillus bacteria in your body are influenced by diet, lifestyle and general health. And like the bifidos, studies have shown that lactobacilli require small amounts of iron for growth depending on the environment they are in, but too much free iron in the intestine from stress, intestinal bleeding, surgery, trauma or dietary supplements can lead to accelerated growth of other, possibly harmful, microbes. Lactobacilli have a hard time competing with those faster-growing microbes, so it is important that you consistently eat, drink or take supplemental probiotics to keep their numbers high.


Some of the species that are explored in this website are:


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