RESEARCH STARTER

Lactobacillus

Lactobacillus is a genus of rod-shaped, Gram-positive bacteria that are facultative anaerobes, meaning they can thrive in environments without oxygen. A notable species within this genus is Lactobacillus acidophilus, which is commonly found in the human gut and other areas, including the female genitals. These bacteria play a crucial role in maintaining digestive health and supporting the immune system, as the human intestine hosts a diverse community of bacteria that assists in food digestion and vitamin production. A balance of these bacteria is essential; disruptions, such as those caused by antibiotic use, can lead to infections and digestive issues.

Historically, Lactobacillus has been utilized in food preservation through fermentation, and studies have linked its consumption to various health benefits, including improved digestion and support for gut health during and after antibiotic treatment. This bacteria also helps maintain vaginal health by regulating pH levels and preventing the overgrowth of yeast. Recent research is exploring innovative therapies involving genetically engineered Lactobacillus strains that may aid in managing conditions such as Type 2 Diabetes. Overall, Lactobacillus is integral to both health and food production, with ongoing studies highlighting its therapeutic potential.

Full Article

Lactobacillus bacteria are rod-shaped, Gram-positive, facultative anaerobes. Lactobacillus acidophilus, which colonizes the gut and other regions of the body (e.g., female genitals), is an important species of bacteria. A healthy human intestine contains billions of between 500 and 1,000 species of harmless bacteria that help digest foods, produce vitamins necessary for a healthy metabolism, and use up resources so that harmful bacteria cannot grow. Gut bacteria play an important role in supporting and regulating the immune system. When this balance is disrupted, such as when an individual receives certain antibiotics and reduces the number and type of bacteria available in the gut, it leaves the individual more susceptible to developing infections and can lead to poor digestion or digestive issues. One important species of bacteria is Lactobacillus acidophilus, which colonizes the gut and other regions of the body (i.e., female genitals). An imbalance of L. acidophilus can lead to an overgrowth of yeast, resulting in an infection. Some evidence suggests that Lactobacillus-containing foods may support vaginal and gut health, but they are not guaranteed to prevent genitourinary problems.

Brief History

For hundreds of years, Lactobacillus bacteria have been used to preserve foods in a process called fermentation. In 1906, Illya Metchnikoff, a Nobel Prize winner, proposed that fermented foods, which are rich in lactobacilli and other lactic acid-producing bacteria, were credited with Balkans’ long life spans. By the 1920s and 1930s, fermented milk products containing Lactobacillus were used experimentally to treat diarrhea in the United States. The results of this treatment were quite successful, which led to a brief attempt to market tablets that claimed to treat diarrhea. The initial attempt, however, yielded non-viable L. acidophilus cultures, and production was halted. In 1990, improved methods permitted packaging the bacteria for improved absorption that would result in more cultures reaching the intestine. However, products placed on the market were inconsistent in dose, and many had bacteria that did not survive stomach acid. In the years after it was identified that L. acidophilus and other intestinal bacteria did not survive stomach acid, compounding companies began using enteric coating, which resists dissolving in the stomach and delivers more live cultures to the intestines.

Aside from the health benefits of L. acidophilus, some Lactobacillus species are used as “starter” cultures for fermentation in industry. The fermentation properties of various Lactobacillus species are used in the production of yogurt, cheese, sauerkraut, pickles, beer, wine, and other fermented foods, as well as animal feeds. A popular use is in the making of sourdough bread. The bacteria are used in a “starter culture,” which is made of yeast and lactic acid bacteria growing in water and flour medium. The signature sour taste of fermented foods is created when the bacteria metabolize sugars into lactic acid, which lowers the pH of their environment.

Overview

Lactobacillus bacteria are rod-shaped, Gram-positive bacteria that are typically aerotolerant anaerobes or facultative anaerobic (thrive in the absence of oxygen). They are part of the normal microbiota of the human mouth, gastrointestinal tract, and genitourinary systems. While Lactobacillus species are normally harmless and help maintain health, there are situations where the presence of the bacteria can cause disease. Lactobacillus can be present in the urinary microbiome. Sometimes the bacteria invade the blood, usually through an infection of the urinary tract or after childbirth. Lactobacillus can cause a condition called bacteremia (bacteria in the blood), which can lead to the bacteria having easy access to organs and tissues. In some cases of Lactobacillus bacteremia, the heart can be affected. This can cause inflammation (endocarditis) and potential valve disorders. Once this type of infection takes place, it is difficult to treat, especially since lactobacilli are resistant to many antibiotics, such as vancomycin.

L. acidophilus can be used to treat certain conditions when the cause is a lack of L. acidophilus in a body system. When an individual has received antibiotics for an infection, the result is often diarrhea. One therapy that is currently used to prevent this condition is to take foods (yogurt or kefir) or a supplement containing L. acidophilus bacteria during and after undergoing antibiotic therapy. This therapy can also help treat the lactose intolerance that is primarily caused by lactase deficiency. Another therapeutic use of L. acidophilus is to help restore the pH balance in the vagina. Often, after taking antibiotics, a female can experience an overgrowth of Candida albicans, a type of yeast that normally inhabits the region, but is normally kept at low levels. L. acidophilus plays a very important role in protecting the vaginal epithelium by creating a thick culture layer that protects the epithelium from pathogens. Lactobacillus metabolism also produces a vaginal pH of ~4.5 that helps keep yeast growth in check.

Other than using L. acidophilus to treat conditions that result from a deficiency in the bacteria, the species is also being used to explore therapies to treat conditions like type 2 diabetes mellitus. In a study conducted by John March at Cornell University, a strain of Lactobacillus was genetically engineered to secrete a glucagon-like peptide (small protein). He and his team were able to demonstrate that insulin control could be moved from the pancreas to the upper intestines in rats. More research is needed to determine the correct dose and safety of using the engineered bacteria in this manner. Preliminary data have indicated that if these parameters are established, type 2 diabetes mellitus could potentially be completely reversed. Though this goal was not achieved during the mid 2020s, research into the effects of Lactobacillus supplementation in individuals with type 2 diabetes mellitus continued. Evidence indicates that Lactobacillus supplementation may improve blood glucose control, insulin resistance, and inflammation, but its effects are modest and variable, and it is not considered a curative treatment for type 2 diabetes mellitus. Advances have enabled precise genetic editing of Lactobacillus strains without introducing foreign deoxyribonucleic acid (DNA), allowing the development of safer, targeted “next-generation probiotics” designed for therapeutic use. Emerging research is exploring the use of engineered Lactobacillus strains, sometimes referred to as “pharmabiotics,” which are designed to produce therapeutic molecules in the body and are being evaluated in early clinical studies for chronic diseases.


Bibliography

Beserra Rosa, Luciana Justo, et al. “Viability of Probiotic Micro-Organism Lactobacillus Acidophilus in Dairy Chocolate Dessert and Its Action Against Foodborne Pathogens.” Ciência Rural, vol. 46, no. 2, 2016, pp. 368–74. Academic Search Complete.

“Breakthrough DNA Editing in Lactobacillus Offers Safer Probiotics.” News-Medical.net, 24 Apr. 2025, www.news-medical.net/news/20250424/Breakthrough-DNA-editing-in-Lactobacillus-offers-safer-probiotics.aspx. Accessed 19 Mar. 2026.

Hickson, Mary, et al. “Use of Probiotic Lactobacillus Preparation to Prevent Diarrhoea Associated with Antibiotics: Randomised Double Blind Placebo Controlled Trial. (Cover Story).” BMJ: British Medical Journal (International Edition), vol. 335, no. 7610, 2007, pp. 80–83. Academic Search Complete.

Hungin, A. P. S., et al. “Systematic Review: Probiotics in the Management of Lower Gastrointestinal Symptoms in Clinical Practice—An Evidence-Based International Guide.” Alimentary Pharmacology & Therapeutics, vol. 38, no. 8, 2013, pp. 864–86. Academic Search Complete.

“Lactobacillus Acidophilus.” MedlinePlus, 4 Dec. 2024, medlineplus.gov/druginfo/natural/790.html. Accessed 7 Mar. 2025.

“Lactose Intolerance.” National Institute of Diabetes and Digestive and Kidney Diseases, U.S. Department of Health and Human Services, www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance. Accessed 19 Mar. 2026.

Li, C., et al. “Effect of the Absence of the Ccpa Gene on Growth, Metabolic Production, and Stress Tolerance in Lactobacillus Delbrueckii Ssp. Bulgaricus.” Journal of Dairy Science, vol. 99, no. 1, 2016, pp. 104–11. Business Source Complete.

“Microbiome Breakthrough: Gut Bacterium May Hold Key to Future Treatments for Widespread Chronic Diseases.” Health Sciences, University of Copenhagen, 1 Aug. 2025, healthsciences.ku.dk/newsfaculty-news/2025/08/microbiome-breakthrough-gut-bacterium-may-hold-key-to-future-treatments-for-widespread-chronic-diseases/. Accessed 19 Mar. 2026.

Ortakci, Fatih, et al. “Growth and Gas Formation by Lactobacillus Wasatchensis, A Novel Obligatory Heterofermentative Nonstarter Lactic Acid Bacterium, In Cheddar-Style Cheese Made Using a Streptococcus Thermophilus Starter.” Journal of Dairy Science, vol. 98, no. 11, 2015, pp. 7473–82. Business Source Complete.

Renhui, Huang, et al. “In Vitro Probiotic Characteristics of Lactobacillus Plantarum ZDY 2013 and Its Modulatory Effect on Gut Microbiota of Mice.” Journal of Dairy Science, vol. 98, no. 9, 2015, pp. 5850–61. Business Source Complete.

Ru, Jia, et al. “Effects of Fermentation with Lactobacillus Rhamnosus GG on Product Quality and Fatty Acids of Goat Milk Yogurt.” Journal of Dairy Science, vol. 99, no. 1, 2016, pp. 221–27. Business Source Complete.

“Study: Lactobacilli Living in Female Urinary Tract’s Microbiome Can Kill Nearby Pathogenic Bacteria.” News‑Medical, 6 July 2022, www.news‑medical.net/news/20220706/Study‑Lactobacilli‑living‑in‑female‑urinary‑tracts‑microbiome‑can‑kill‑nearby‑pathogenic‑bacteria.aspx. Accessed 19 Mar. 2026.

Wang, Guang. “Efficacy of Lactobacillus Paracasei LC19 on Type 2 Diabetes.” ICHGCP.net, 5 Feb. 2025, ichgcp.net/clinical-trials-registry/NCT06639425. Accessed 19 Mar. 2026.

Wenjun, Liu, et al. “Relationships Between Functional Genes in Lactobacillus Delbrueckii Ssp. Bulgaricus Isolates and Phenotypic Characteristics Associated with Fermentation Time and Flavor Production in Yogurt Elucidated Using Multilocus Sequence Typing.” Journal of Dairy Science, vol. 99, no. 1, 2016, 89–103. Business Source Complete.

Full Article

Lactobacillus bacteria are rod-shaped, Gram-positive, facultative anaerobes. Lactobacillus acidophilus, which colonizes the gut and other regions of the body (e.g., female genitals), is an important species of bacteria. A healthy human intestine contains billions of between 500 and 1,000 species of harmless bacteria that help digest foods, produce vitamins necessary for a healthy metabolism, and use up resources so that harmful bacteria cannot grow. Gut bacteria play an important role in supporting and regulating the immune system. When this balance is disrupted, such as when an individual receives certain antibiotics and reduces the number and type of bacteria available in the gut, it leaves the individual more susceptible to developing infections and can lead to poor digestion or digestive issues. One important species of bacteria is Lactobacillus acidophilus, which colonizes the gut and other regions of the body (i.e., female genitals). An imbalance of L. acidophilus can lead to an overgrowth of yeast, resulting in an infection. Some evidence suggests that Lactobacillus-containing foods may support vaginal and gut health, but they are not guaranteed to prevent genitourinary problems.

Brief History

For hundreds of years, Lactobacillus bacteria have been used to preserve foods in a process called fermentation. In 1906, Illya Metchnikoff, a Nobel Prize winner, proposed that fermented foods, which are rich in lactobacilli and other lactic acid-producing bacteria, were credited with Balkans’ long life spans. By the 1920s and 1930s, fermented milk products containing Lactobacillus were used experimentally to treat diarrhea in the United States. The results of this treatment were quite successful, which led to a brief attempt to market tablets that claimed to treat diarrhea. The initial attempt, however, yielded non-viable L. acidophilus cultures, and production was halted. In 1990, improved methods permitted packaging the bacteria for improved absorption that would result in more cultures reaching the intestine. However, products placed on the market were inconsistent in dose, and many had bacteria that did not survive stomach acid. In the years after it was identified that L. acidophilus and other intestinal bacteria did not survive stomach acid, compounding companies began using enteric coating, which resists dissolving in the stomach and delivers more live cultures to the intestines.

Aside from the health benefits of L. acidophilus, some Lactobacillus species are used as “starter” cultures for fermentation in industry. The fermentation properties of various Lactobacillus species are used in the production of yogurt, cheese, sauerkraut, pickles, beer, wine, and other fermented foods, as well as animal feeds. A popular use is in the making of sourdough bread. The bacteria are used in a “starter culture,” which is made of yeast and lactic acid bacteria growing in water and flour medium. The signature sour taste of fermented foods is created when the bacteria metabolize sugars into lactic acid, which lowers the pH of their environment.

Overview

Lactobacillus bacteria are rod-shaped, Gram-positive bacteria that are typically aerotolerant anaerobes or facultative anaerobic (thrive in the absence of oxygen). They are part of the normal microbiota of the human mouth, gastrointestinal tract, and genitourinary systems. While Lactobacillus species are normally harmless and help maintain health, there are situations where the presence of the bacteria can cause disease. Lactobacillus can be present in the urinary microbiome. Sometimes the bacteria invade the blood, usually through an infection of the urinary tract or after childbirth. Lactobacillus can cause a condition called bacteremia (bacteria in the blood), which can lead to the bacteria having easy access to organs and tissues. In some cases of Lactobacillus bacteremia, the heart can be affected. This can cause inflammation (endocarditis) and potential valve disorders. Once this type of infection takes place, it is difficult to treat, especially since lactobacilli are resistant to many antibiotics, such as vancomycin.

L. acidophilus can be used to treat certain conditions when the cause is a lack of L. acidophilus in a body system. When an individual has received antibiotics for an infection, the result is often diarrhea. One therapy that is currently used to prevent this condition is to take foods (yogurt or kefir) or a supplement containing L. acidophilus bacteria during and after undergoing antibiotic therapy. This therapy can also help treat the lactose intolerance that is primarily caused by lactase deficiency. Another therapeutic use of L. acidophilus is to help restore the pH balance in the vagina. Often, after taking antibiotics, a female can experience an overgrowth of Candida albicans, a type of yeast that normally inhabits the region, but is normally kept at low levels. L. acidophilus plays a very important role in protecting the vaginal epithelium by creating a thick culture layer that protects the epithelium from pathogens. Lactobacillus metabolism also produces a vaginal pH of ~4.5 that helps keep yeast growth in check.

Other than using L. acidophilus to treat conditions that result from a deficiency in the bacteria, the species is also being used to explore therapies to treat conditions like type 2 diabetes mellitus. In a study conducted by John March at Cornell University, a strain of Lactobacillus was genetically engineered to secrete a glucagon-like peptide (small protein). He and his team were able to demonstrate that insulin control could be moved from the pancreas to the upper intestines in rats. More research is needed to determine the correct dose and safety of using the engineered bacteria in this manner. Preliminary data have indicated that if these parameters are established, type 2 diabetes mellitus could potentially be completely reversed. Though this goal was not achieved during the mid 2020s, research into the effects of Lactobacillus supplementation in individuals with type 2 diabetes mellitus continued. Evidence indicates that Lactobacillus supplementation may improve blood glucose control, insulin resistance, and inflammation, but its effects are modest and variable, and it is not considered a curative treatment for type 2 diabetes mellitus. Advances have enabled precise genetic editing of Lactobacillus strains without introducing foreign deoxyribonucleic acid (DNA), allowing the development of safer, targeted “next-generation probiotics” designed for therapeutic use. Emerging research is exploring the use of engineered Lactobacillus strains, sometimes referred to as “pharmabiotics,” which are designed to produce therapeutic molecules in the body and are being evaluated in early clinical studies for chronic diseases.


Bibliography

Beserra Rosa, Luciana Justo, et al. “Viability of Probiotic Micro-Organism Lactobacillus Acidophilus in Dairy Chocolate Dessert and Its Action Against Foodborne Pathogens.” Ciência Rural, vol. 46, no. 2, 2016, pp. 368–74. Academic Search Complete.

“Breakthrough DNA Editing in Lactobacillus Offers Safer Probiotics.” News-Medical.net, 24 Apr. 2025, www.news-medical.net/news/20250424/Breakthrough-DNA-editing-in-Lactobacillus-offers-safer-probiotics.aspx. Accessed 19 Mar. 2026.

Hickson, Mary, et al. “Use of Probiotic Lactobacillus Preparation to Prevent Diarrhoea Associated with Antibiotics: Randomised Double Blind Placebo Controlled Trial. (Cover Story).” BMJ: British Medical Journal (International Edition), vol. 335, no. 7610, 2007, pp. 80–83. Academic Search Complete.

Hungin, A. P. S., et al. “Systematic Review: Probiotics in the Management of Lower Gastrointestinal Symptoms in Clinical Practice—An Evidence-Based International Guide.” Alimentary Pharmacology & Therapeutics, vol. 38, no. 8, 2013, pp. 864–86. Academic Search Complete.

“Lactobacillus Acidophilus.” MedlinePlus, 4 Dec. 2024, medlineplus.gov/druginfo/natural/790.html. Accessed 7 Mar. 2025.

“Lactose Intolerance.” National Institute of Diabetes and Digestive and Kidney Diseases, U.S. Department of Health and Human Services, www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance. Accessed 19 Mar. 2026.

Li, C., et al. “Effect of the Absence of the Ccpa Gene on Growth, Metabolic Production, and Stress Tolerance in Lactobacillus Delbrueckii Ssp. Bulgaricus.” Journal of Dairy Science, vol. 99, no. 1, 2016, pp. 104–11. Business Source Complete.

“Microbiome Breakthrough: Gut Bacterium May Hold Key to Future Treatments for Widespread Chronic Diseases.” Health Sciences, University of Copenhagen, 1 Aug. 2025, healthsciences.ku.dk/newsfaculty-news/2025/08/microbiome-breakthrough-gut-bacterium-may-hold-key-to-future-treatments-for-widespread-chronic-diseases/. Accessed 19 Mar. 2026.

Ortakci, Fatih, et al. “Growth and Gas Formation by Lactobacillus Wasatchensis, A Novel Obligatory Heterofermentative Nonstarter Lactic Acid Bacterium, In Cheddar-Style Cheese Made Using a Streptococcus Thermophilus Starter.” Journal of Dairy Science, vol. 98, no. 11, 2015, pp. 7473–82. Business Source Complete.

Renhui, Huang, et al. “In Vitro Probiotic Characteristics of Lactobacillus Plantarum ZDY 2013 and Its Modulatory Effect on Gut Microbiota of Mice.” Journal of Dairy Science, vol. 98, no. 9, 2015, pp. 5850–61. Business Source Complete.

Ru, Jia, et al. “Effects of Fermentation with Lactobacillus Rhamnosus GG on Product Quality and Fatty Acids of Goat Milk Yogurt.” Journal of Dairy Science, vol. 99, no. 1, 2016, pp. 221–27. Business Source Complete.

“Study: Lactobacilli Living in Female Urinary Tract’s Microbiome Can Kill Nearby Pathogenic Bacteria.” News‑Medical, 6 July 2022, www.news‑medical.net/news/20220706/Study‑Lactobacilli‑living‑in‑female‑urinary‑tracts‑microbiome‑can‑kill‑nearby‑pathogenic‑bacteria.aspx. Accessed 19 Mar. 2026.

Wang, Guang. “Efficacy of Lactobacillus Paracasei LC19 on Type 2 Diabetes.” ICHGCP.net, 5 Feb. 2025, ichgcp.net/clinical-trials-registry/NCT06639425. Accessed 19 Mar. 2026.

Wenjun, Liu, et al. “Relationships Between Functional Genes in Lactobacillus Delbrueckii Ssp. Bulgaricus Isolates and Phenotypic Characteristics Associated with Fermentation Time and Flavor Production in Yogurt Elucidated Using Multilocus Sequence Typing.” Journal of Dairy Science, vol. 99, no. 1, 2016, 89–103. Business Source Complete.

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