Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. The vast world of probiotics includes many different types of bacteria, each with distinct functions and effects on the human body. Understanding the various bacterial families and specific strains can help consumers make informed choices for their health needs.
Common Probiotic Bacteria Families
Lactobacillus
This is perhaps the most famous and widely used group of probiotic bacteria, commonly found in fermented foods like yogurt and kimchi. Members of this genus are lactic acid bacteria, meaning they ferment sugars into lactic acid. This creates an acidic environment in the gut that can be inhospitable to many pathogenic bacteria. A recent revision of bacterial taxonomy split this large genus into 25 smaller genera, though the name is still frequently used.
Common Lactobacillus species used as probiotics include:
- Lactobacillus acidophilus: Often found in yogurt and dairy, this strain is well-known for its role in digestion and promoting a healthy intestinal environment.
- Lacticaseibacillus rhamnosus (formerly Lactobacillus rhamnosus): The famous strain L. rhamnosus GG (LGG) is a well-researched strain known for its ability to survive gastric transit and support the gut lining, particularly during antibiotic use.
- Lactiplantibacillus plantarum (formerly Lactobacillus plantarum): Found in fermented foods like sauerkraut and kimchi, certain strains are studied for their potential to support digestive comfort and cardiovascular health.
- Lacticaseibacillus casei (formerly Lactobacillus casei): Used in cheese and yogurt, specific strains like L. casei Shirota are known for aiding in digestive regularity.
Bifidobacterium
Another major group of beneficial bacteria, Bifidobacteria are among the first microbes to colonize the human gut, especially in breastfed infants. They are specialized at fermenting dietary fibers and complex carbohydrates that humans cannot digest alone, producing beneficial compounds called short-chain fatty acids (SCFAs).
Common Bifidobacterium species include:
- Bifidobacterium lactis: Found in dairy products and supplements, strains of B. lactis have been shown to support digestive regularity, enhance immune function, and help the microbiome recover after antibiotic use.
- Bifidobacterium longum: This species is a key fermenter of dietary fiber and has been researched for its ability to support psychological health via the gut-brain axis, as well as aid in digestive regularity.
- Bifidobacterium bifidum: A resident of the intestines, B. bifidum produces lactic and acetic acid and can help with digestive and respiratory issues.
Bacillus
Unlike Lactobacillus and Bifidobacterium, Bacillus species are spore-forming bacteria, which makes them highly resistant to harsh conditions like high temperatures, stomach acid, and bile. This resilience ensures that they can survive manufacturing and transit through the digestive system to exert their effects.
Common Bacillus species include:
- Bacillus subtilis: This soil-dwelling bacterium is naturally found in the human gut and has been studied for its ability to produce enzymes, improve gut flora, and support immune responses. It is used in the production of the Japanese food nattō.
- Bacillus coagulans: This is a highly stable, spore-forming probiotic often used to manage diarrhea and promote digestive health.
Streptococcus
Certain strains of Streptococcus are considered beneficial and are used in probiotic products and fermented foods. Notably, Streptococcus thermophilus is a thermophilic (heat-loving) bacterium used as a starter culture alongside Lactobacillus delbrueckii subsp. bulgaricus to make yogurt. It is recognized as 'Generally Recognized as Safe' (GRAS) by the FDA.
Other Beneficial Microbes
Saccharomyces boulardii (Yeast)
While not a bacterium, this beneficial yeast is often included in probiotic formulations. It is particularly known for its ability to help restore gut health during episodes of diarrhea, including that caused by antibiotics. As a yeast, it is not affected by antibacterial antibiotics, making it an ideal choice for this purpose.
Probiotic Bacteria Comparison Table
| Bacteria Family | Common Species/Strains | Primary Role & Benefits | Common Food Sources |
|---|---|---|---|
| Lactobacillus | L. acidophilus, L. rhamnosus GG, L. plantarum | Produces lactic acid, aids digestion, supports gut lining, enhances immunity | Yogurt, kefir, fermented foods, supplements |
| Bifidobacterium | B. lactis, B. longum, B. bifidum | Ferments fiber into SCFAs, supports gut-brain axis, promotes regularity | Yogurt, kefir, fermented milk, supplements |
| Bacillus | B. subtilis, B. coagulans | Highly stable spore-former, produces enzymes, supports immunity | Fermented soy (nattō), supplements |
| Streptococcus | S. thermophilus | Ferments lactose, used in yogurt, aids digestion | Yogurt, other fermented dairy |
| Saccharomyces (Yeast) | S. boulardii | Restores gut health, effective during antibiotic-associated diarrhea | Supplements, kefir |
The Importance of Strain Specificity
As highlighted in the table, the benefits of a probiotic are highly specific to the individual strain, not just the genus. For example, one strain of Lactobacillus might excel at improving digestive regularity, while another might be more effective at supporting skin health. Reputable probiotic supplements will list the full, specific strain name (e.g., L. rhamnosus GG) on the label, which indicates the product has been studied for its claimed benefits. For instance, a pharmacist might recommend a yeast strain like Saccharomyces boulardii for antibiotic-associated diarrhea because antibiotics won't kill it, whereas a bacterial strain may be less effective when taken concurrently. Conversely, if the goal is to repopulate the bacterial flora after a course of antibiotics, specific Bifidobacterium or Lactobacillus strains would be appropriate. Always verify that the strain listed is supported by research for your intended use.
Conclusion
The diverse and complex world of probiotic microorganisms offers a variety of potential health benefits, most notably dominated by the bacterial genera Lactobacillus and Bifidobacterium. Other key players include the highly stable, spore-forming Bacillus species and beneficial yeasts like Saccharomyces boulardii. The crucial takeaway for consumers is to look beyond the general genus and identify the specific strain, as this is where the clinically proven benefits lie. Whether seeking to improve digestion, support immune function, or aid recovery from illness, understanding which microbes are used as probiotics is the first step toward a healthier gut.
For more information on probiotics, visit the National Center for Complementary and Integrative Health: https://www.nccih.nih.gov/health/probiotics-usefulness-and-safety.
