Lactobacillus acidophilus bacteria are gram positive bacteria found naturally in the human digestive tract. These organisms are among a group known as lactic acid bacteria because they survive by breaking down sugars into lactic acid, producing a number of useful byproducts along the way. In the intestine, they help people digest a variety of foods and their waste products contribute nutritional value by providing people with vitamins and minerals like vitamin K. These bacteria are also known as “probiotic” or “friendly” bacteria since they have health benefits, unlike pathogenic bacteria that make people sick.
As the name implies, Lactobacillus acidophilus bacteria are associated with milk and other dairy products, and they love highly acidic environments. When people ferment milk to make cultured dairy products like yogurt and cheese, these bacteria are often present. As they work, they raise the acidity of the culture, inhibiting the growth of harmful bacteria that prefer more neutral environments. This makes cultured and other fermented foods resistant to infectious organisms, one reason why many societies have a long history of using fermentation in food preservation.
In the body, in addition to producing nutritionally useful substances, Lactobacillus acidophilus bacteria keep acidity high, suppressing the growth of unwanted bacteria. In the mouth, it will fight off infections with yeasts like those that cause thrush, and it can also prevent or fight yeast infections of the genitals. This is one reason people with yeast infections are sometimes advised to eat yogurt with live active cultures or to take an acidophilus supplement that contains Lactobacillus acidophilus bacteria.
This organism has been a topic of intensive study by researchers interested in how it behaves in the body, as well as people studying its role in food fermentation and preservation. Researchers have learned a great deal about the conditions it prefers and how it interacts with other organisms. This has led to the development of a number of probiotic supplement products, sold to promote digestive health. People should be aware that such supplements are variable in terms of efficacy and quality; sometimes the Lactobacillus acidophilus bacteria inside are dead, and in other cases, they may not be that beneficial in terms of treating or preventing disease.
People interested in looking at Lactobacillus acidophilus bacteria can find slides online, many of which are stained to provide clearer visual information. For those who like things more up close and personal and have access to high resolution microscopes, samples of yogurt with live cultures or other traditionally fermented foods can be examined to reveal their bacterial residents. This bacterium is easy to spot, with its distinctive rod-like shape.