Are Lactobacillus and Lactic Acid Bacteria the Same?

January 13, 2026 •

3 min read

Scientific research confirms that while all Lactobacillus are a type of lactic acid bacteria, the reverse is not true, revealing a crucial classification difference. This relationship is similar to how all poodles are dogs, but not all dogs are poodles. Understanding this distinction is key to comprehending the world of probiotics, fermented foods, and gut health.

Quick Summary

Lactobacillus is a genus of bacteria that falls under the much broader category of lactic acid bacteria (LAB). LAB encompasses many genera, all characterized by their ability to ferment carbohydrates into lactic acid. This article clarifies the hierarchical relationship, detailing the distinct characteristics, examples, and roles of both groups.

Key Points

Genus vs. Group: Lactobacillus is a specific genus within the broader, functional group known as lactic acid bacteria (LAB).
All vs. Not All: All Lactobacillus species are lactic acid bacteria, but not all lactic acid bacteria are Lactobacillus.
Diverse Family: The LAB group includes many other genera, such as Lactococcus, Streptococcus, and Pediococcus, besides Lactobacillus.
Reclassification: The single genus Lactobacillus was recently reclassified into 25 distinct genera to reflect its extensive diversity.
Food Production: LAB, including Lactobacillus, are essential for producing fermented foods like yogurt, cheese, and sauerkraut.
Probiotic Benefits: Specific strains of Lactobacillus are well-known probiotics that support gut health, enhance immunity, and aid digestion.
Metabolic Trait: The unifying characteristic for all LAB is their ability to ferment carbohydrates into lactic acid.
Acidic Environment: Lactic acid production by these bacteria creates an acidic environment that helps preserve food and inhibits harmful pathogens.

Understanding the Difference: Genus vs. Group

At the core of the confusion is a fundamental microbiological concept: the difference between a taxonomic genus and a broader functional group. The term "lactic acid bacteria" (LAB) is not a single genus but a functional designation given to a diverse group of bacteria from multiple genera that share a metabolic trait—the ability to produce lactic acid through fermentation. Lactobacillus, conversely, is a specific genus within this larger group, encompassing many individual species.

The Broad Group of Lactic Acid Bacteria

Lactic acid bacteria are Gram-positive, non-spore-forming bacteria that produce lactic acid from the fermentation of carbohydrates. This metabolic activity is widely harnessed in the food industry for preservation and to develop unique flavors and textures. The LAB group is extensive and includes many well-known genera besides Lactobacillus:

Lactococcus: Known for its use in cheese production, such as Lactococcus lactis.
Streptococcus: Includes Streptococcus thermophilus, a crucial starter culture for yogurt alongside certain Lactobacillus species.
Leuconostoc: Often involved in the fermentation of vegetables, such as sauerkraut, and used in dairy products.
Pediococcus: Found in fermented vegetables and meat products.
Enterococcus: Present in fermented foods and part of the human microbiome.
Bifidobacterium: A distinct genus also known for probiotic properties, though not always grouped with LAB.

The Specific Genus Lactobacillus

For a long time, the genus Lactobacillus was one of the largest and most diverse genera within the LAB group. Due to this extensive diversity, a 2020 taxonomic revision reclassified the genus, splitting it into 25 new or existing genera. This reclassification does not change the bacteria's function but provides a more precise and accurate scientific naming system. Some of the well-known species were moved to new genera, for example:

Lactobacillus casei is now Lacticaseibacillus casei.
Lactobacillus plantarum is now Lactiplantibacillus plantarum.
Lactobacillus rhamnosus is now Lacticaseibacillus rhamnosus.

Despite these changes, the original name is still widely used in common parlance and on many probiotic product labels. The bacteria within the Lactobacillus sensu stricto (original, strict sense) genus are typically rod-shaped and can be either homofermentative (producing mainly lactic acid) or heterofermentative (producing lactic acid, carbon dioxide, and ethanol).

Comparison: Lactobacillus vs. Lactic Acid Bacteria


Feature	Lactic Acid Bacteria (LAB)	Lactobacillus
Scope	A broad, functional group comprising many genera.	A specific genus (or now, a collection of 25 genera) within the larger LAB group.
Taxonomic Rank	A functional group, not a formal taxonomic classification like genus or family.	A specific genus under the family Lactobacillaceae and order Lactobacillales.
Key Characteristic	All members produce lactic acid as a major metabolic byproduct.	All species within this genus produce lactic acid. The older, broader definition also included heterofermentative strains.
Composition	Includes genera such as Lactobacillus, Lactococcus, Streptococcus, Leuconostoc, and Pediococcus.	Contains species formerly classified under the single Lactobacillus genus, now split into 25 distinct genera.
Examples	Found in yogurt, cheese, sauerkraut, and sourdough bread.	Includes well-known probiotic species such as Lacticaseibacillus rhamnosus (formerly L. rhamnosus) and Lacticaseibacillus casei (formerly L. casei).
Metabolism	Can be either homofermentative or heterofermentative.	Can be either homofermentative or heterofermentative, depending on the species.

Their Role in Food and Gut Health

Both Lactobacillus and other lactic acid bacteria play indispensable roles in our daily lives, particularly concerning food production and digestive wellness. In fermented foods, LAB inhibit the growth of harmful bacteria and contribute to the final product's distinct flavor and texture. For example, in yogurt production, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus work together to ferment milk into yogurt.

As probiotics, certain strains of Lactobacillus and Bifidobacterium have been extensively studied for their health-promoting properties. Their ability to survive the harsh conditions of the gastrointestinal tract allows them to modulate the gut microbiome, which has numerous benefits, including improved digestion, boosted immunity, and reduced inflammation. By producing lactic acid, they create an acidic environment that is unfavorable for many pathogens, reinforcing the body's natural defenses.

Conclusion

The critical distinction is that 'lactic acid bacteria' is a comprehensive functional term, while Lactobacillus refers to a specific genus (now a group of 25) within that functional group. This means all lactobacilli are, by definition, lactic acid bacteria, but not all lactic acid bacteria are lactobacilli. For consumers, this highlights the importance of looking beyond the general term to understand the specific genus and species within a probiotic product, as different strains offer distinct health benefits. In the scientific and industrial world, recognizing this hierarchical classification is essential for accurate research, food production, and health applications.

Frequently Asked Questions

The primary difference is one of classification; Lactobacillus is a specific genus of bacteria, while lactic acid bacteria (LAB) is a broad functional group that includes Lactobacillus and many other genera of bacteria.

Not all lactic acid bacteria are considered probiotics. A bacterium is only considered a probiotic if it confers a specific health benefit to the host when consumed in adequate amounts. While many probiotic strains belong to the LAB group, not every LAB strain has proven probiotic effects.

Besides Lactobacillus, other genera belonging to the lactic acid bacteria group include Lactococcus, Streptococcus, Leuconostoc, and Pediococcus.

The genus Lactobacillus was reclassified into 25 different genera in 2020 due to its immense genetic and metabolic diversity, making it difficult to accurately classify under a single genus. The new classifications provide a more precise representation of these bacterial species.

In fermented foods like yogurt and cheese, lactic acid bacteria convert sugars into lactic acid, which increases acidity. This process acts as a natural preservative, inhibits the growth of spoilage microorganisms, and contributes to the food's unique flavor and texture.

Yes, many fermented foods are rich in lactic acid bacteria. These include yogurt, kefir, sauerkraut, pickles, sourdough bread, and certain cheeses.

Lactobacilli support gut health by producing lactic acid, which lowers the intestinal pH and creates an unfavorable environment for harmful bacteria. They also compete for nutrients and adhesion sites, produce antimicrobial compounds, and support the immune system.

A healthy gut microbiome thrives on a diverse range of beneficial bacteria. While many probiotic supplements focus on Lactobacillus, consuming a varied diet rich in fermented foods can provide a broader spectrum of lactic acid bacteria and other beneficial microorganisms.