Lactobacillus

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 500–1,000 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. In fact, these bacteria make up about 70 percent of human immunity. 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. It is important for women, in particular, to make sure they consume foods rich in L. acidophilus cultures to avoid genitourinary problems.

Brief History

For hundreds of years Lactobacillus bacteria has been used to preserve foods in a process called fermentation. In 1906, Illya Metchnikoff, a Nobel Prize winner, demonstrated that fermented foods, which are rich in lactobacilli and other lactic acid-producing bacteria, was credited with Balkans’ long life spans. By the 1920s and 1930s, Lactobacillus milk (a form of kefir) was used to treat diarrhea in the U.S. 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 (about 20 minutes) 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 L. acidophilus are used in the production of yogurt, cheese, sauerkraut, pickles, beer, wine, and other fermented foods, as well as animal feeds. A popular use of L. acidophilus 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 a 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, facultative anaerobes (thrive in the absence of oxygen). They are part of the normal flora 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 cannot grow in urine, so their numbers are usually kept in check. However, 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. A common organ that is affected in lactobacillus bacteremia is the heart. 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 often results from the loss of bacteria in the intestines. 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 Candidia 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 metabolim also produce 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 Diabetes Mellitus Type 2. In a study conducted by John March at Cornell University, a strain of Lactobacillus was genetically engineered to secrete a peptide (small protein) that releases insulin from the pancreas. He and his team were able to demonstrate that insulin control could be moved from the pancreas to the large intestines in rats. More studies are underway to determine the correct dose and safety of using the engineered bacteria in this manner. Preliminary data has indicated that if these parameters are established, Diabetes Mellitus Type 2 could potentially be completely reversed.

Bibliography

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