Bacteria in the digestive system number in the trillions, and most of these bacteria are referred to as friendly. Some experts say that friendly bacteria have a symbiotic relationship with their human hosts, because they help the human body in a variety of useful ways. Other types of bacteria in the digestive system are not so friendly, including those that produce cholera, botulism and salmonellosis.
Varying estimates indicate that there are 300 to 1,000 species of bacteria in the digestive system. In general, these bacteria, also known as gut flora, help the body in a number of ways that include aiding digestion, strengthening the immune system, and blocking the growth of unfriendly organisms. Friendly bacteria live mostly in the large intestine and part of the small intestine. The acidic environment of the stomach is not conducive to bacterial growth.
Bacteria begin to populate the human digestive system right after birth. One of the most common bacteria, according to experts, are Bacteroides. These bacteria aid in the digestion of plant food like spinach. Bacteroides release enzymes that the human body lacks, and by doing so the nutrients from plant foods can be absorbed. The human body gets vitamin K and some B vitamins due to the work of Bacteroides.
Lactobacillus is another type of friendly bacteria. Found in many food, such as yogurt, beer, wine and chocolate, Lactobacillus bacteria have a reputation for helping the immune system and fending off diseases like the flu. Some research seems to indicate that Lactobacillus has cancer-fighting properties as well. Lactobacillus has been shown to inhibit tumor growth when given to animals.
Some bacteria in the digestive system have a reputation for being very unfriendly and wreaking a lot of havoc. Examples include Vibrio cholera, Clostridium botulinum and several types of Salmonella bacteria. The diseases caused by these bacteria may sometimes be deadly.
Vibrio cholera, the source of cholera, can be spread through drinking water. Its symptoms include diarrhea and dehydration, with severe dehydration being one of the most common causes of death from this disease. Clostridium botulinum produces the very deadly disease botulism by releasing toxins that can initiate muscle paralysis, blurred vision and respiratory distress in addition to diarrhea and vomiting. Salmonella poisoning causes vomiting and diarrhea, which occurs from eating infected eggs, meat and processed foods. This bacteria produces a disease that is self-limiting, meaning the body will usually fight off the disease on its own.