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Science & Nature • Bacteria

Lactobacillus

Lactobacillus is a genus of gram-positive bacteria in the family Lactobacillaceae.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Lactobacillus is a genus of gram-positive bacteria in the family Lactobacillaceae. Its species are typically rod-shaped, non-spore-forming, and known for producing lactic acid from carbohydrate fermentation. Many species are associated with fermented foods and with the human gut and genitourinary tract.

Characteristics

Lactobacillus species are typically gram-positive, rod-shaped, and non-spore-forming bacteria. They are known for converting sugars into lactic acid during fermentation.

Ecology and human association

Members of the genus are found in environments rich in carbohydrates, including fermented foods and the human gastrointestinal and genitourinary tracts. Some species are part of normal human microbiota.

Food and industrial use

Lactobacillus species are important in the production of fermented foods such as yoghurt, cheese, sourdough, and other fermented products. Their acid-producing ability helps preserve food and shape flavour.

Taxonomy

Lactobacillus belongs to the family Lactobacillaceae and is part of the broader group of lactic acid bacteria. The genus has been revised in modern bacterial taxonomy, with many species reassigned to other genera.

Key facts

  • Lactobacillus is a genus of gram-positive, rod-shaped bacteria that produce lactic acid.
  • Species are widely used in food production, especially dairy fermentation.
  • Many species occur naturally in the human digestive tract and vagina.
  • The genus has been subject to taxonomic reclassification.
  • Lactobacillus species are generally aerotolerant anaerobes or microaerophiles.
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Canadian context

Lactobacillus is relevant to Canadian readers through its role in yogurt, cheese, and other fermented foods, as well as through its use in probiotic products and microbiology research.

Frequently asked questions

What is Lactobacillus?
Lactobacillus is a genus of gram-positive, rod-shaped bacteria that produce lactic acid and are part of the family Lactobacillaceae.
Are Lactobacillus bacteria harmful?
Most Lactobacillus species are not known to cause disease and are commonly associated with normal human microbiota and fermented foods.
Where are Lactobacillus bacteria found?
They are found in fermented foods and in the human gastrointestinal and genitourinary tracts, including the mouth and vagina.
Why are Lactobacillus species important in food production?
They ferment carbohydrates into lactic acid, which is useful in making foods such as yoghurt and cheese and helps inhibit unwanted microbes.
Is Lactobacillus a single species?
No. It is a genus, meaning it includes many species.

References

  1. Encyclopaedia Britannica — https://www.britannica.com/science/Lactobacillus
    Supports: Genus description, gram-positive rod-shaped non-spore-forming bacteria, lactic acid production
  2. Wikipedia — https://en.wikipedia.org/wiki/Lactobacillus
    Supports: Family Lactobacillaceae, aerotolerant anaerobes or microaerophilic, rod-shaped, non-endospore-forming
  3. National Cancer Institute — https://www.cancer.gov/publications/dictionaries/cancer-terms/def/lactobacillus
    Supports: Lactic acid production, usual locations in mouth, gastrointestinal tract, and vagina, generally not disease-causing
  4. ScienceDirect Topics — https://www.sciencedirect.com/topics/food-science/lactobacillus
    Supports: Food and industrial uses, classification, lactic acid bacteria context, use in fermented foods
  5. ScienceDirect Topics — https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/lactobacillus
    Supports: Genus characteristics, carbohydrate fermentation, presence in human and animal gastrointestinal tracts
  6. Encyclopedia.com — https://www.encyclopedia.com/plants-and-animals/microbes-algae-and-fungi/moneran-and-protistan/lactobacillus
    Supports: General description, lactic acid end product, role in food technology