Healthy Bacteria There are a number of bacterial species living in our large intestines that we would be nutritionally lost without. The large intestine is home to most of the bacteria in our guts, and it is where these bacteria aid in the digestion of food and the absorption of vitamins and minerals. Examples of such bacteria are clostridium, E. coli, some streptococcus species that break down sugars, and Lactobacillus acidophilus, which is necessary for the breakdown of ingested lactose, a protein found in dairy products, as well as the formation of Vitamin K and folic acid. The helpful bacteria in the gut also prevent colonization by infectious bacteria. The colonies compete for resources and space, minimizing the impact of ingested pathogens. Antibiotic therapy kills some of the intestinal flora, the helpful bacteria, in addition to the illness being treated, making a person more susceptible to illness and digestive problems until the colonies grow back. A new approach to preventing digestive problems and the damage caused by antibiotics is the ingestion of probiotics, a mixture of commensal bacteria to aid in re-colonizing the gut. Humans obtain the gut flora as newborns by breastfeeding, as well as during birth from both the mother and environment. The immune response is not fully developed until approximately 9 months of age, giving the bacteria time to make a hospitable home. Unhealthy Bacteria From time to time, the bacteria that cohabitate with us peacefully in the digestive tract may be introduced to parts of the body that cannot tolerate the organism. An example would be introduction into the bloodstream during gastrointestinal surgery or aspiration into the lungs. The usually helpful bacteria then cause infection. A recent study also found that some of the bacterial organisms colonizing our guts have genes that are associated with digestive disorders, diabetes, and obesity. Previously, the bacterial species Heliobacter pylori was associated with stomach ulcer formation. Though this bacterium is present in more than half of the world
