Bacteria: Friend, Foe or all of the above?

Remember the episode of the Cosby Show, when Rudy catches a cold and Cliff has to take care of her? Cliff’s characterization of what made Rudy sick is probably a common experience and is most likely the first lesson we received about “germs” and their effects. Bacteria have and continue to get a bad rap as only a cause of disease. But did you know that bacteria have positive effects on the lives of humans and other higher organisms? I always begin my beneficial effects of bacteria lecture by posing that question to my students. The most common reaction to my question is disbelief, as if I had just shattered everything they ever learned. The look on their faces says it all: “Bacteria can be useful?” And I commence to explain how this is possible. I think that the reaction that I receive on a consistent basis from students and even from the public at large, that bacteria are all bad, period. I am not saying that the perception is all wrong but the majority of people have it half right and only focus on the ill-effects of bacteria. What are the benefits of bacteria and how do these benefits impact human life?

The relationship between humans and bacteria when beneficial is characterized as commensal or a relationship where neither human nor bacteria is harmed. Bacteria found in and on humans grow and survive with no problems and begin to engage in biological activities which assist human life. One of the most important activities bacteria engage in is protection and immunity from disease. Human skin is the largest and most important body organ. Skin protects muscle, bone and tissue from damage due to everyday movement, sunlight and disease. In addition to the oils naturally secreted by the skin and sweat which contains an enzyme that assists in killing pathogenic or disease causing bacteria, bacterial cells occupy the skin in large numbers. Although bacteria have no problem growing and surviving on the skin, skin is a very poor growth medium because it has a very low pH and is very dry. A large number of bacterial species occupy the skin and maintain a protective barrier against disease causing bacteria. This is only the first line of defense, a disease causing bacteria that enters the skin will trigger an immune reaction which begins a vigorous, second line of defense in fighting off a potential infection.

The human digestive system also benefits greatly from the activity of bacteria. When food is taken in and digested, only a certain amount of nutrients can be taken up from the food by the body. The body needs and requires a number of vitamins, minerals, proteins and carbohydrates in order to maintain function and growth. Many of these are available in food directly while others are available but are not able to be used unless they are converted into another form. Bacteria act as the means by which some of these “hidden” nutrients and vitamins are extracted and put into use by the body. Think of bacteria as “factories” which help to break down food, take in the vitamins and nutrients in their inactive form and convert them to the active form that can be taken in and used by humans.

Within the last 15-20 years, there has been a steady increase in the availability of probiotics, supplements of bacterial cultures that when used properly can provide health benefits. Probiotics are not new as they were first identified in the early 20th Century as a method to assist in maintainance of balance between beneficial and harmful bacteria. Further research has shown that probiotics can also help with digestive ailments such as Irritable Bowel Syndrome (IBS), Diarrhea and reduce the chances of ulcers caused by a bacteria named Helicobacter pylori (H. pylori). Research into the use of probiotics have been very positive. Many people benefit greatly from their use. There are issues of safety which have not been fully studied and mild side effects do occur such as gas, bloating or a mild bacterial infection. Probiotics and their use illustrate the point very effectively that maintaining a balance in the normal types of bacteria that live in the digestive system with those that could cause harm is a very important function. When harmful bacteria are not kept in check by equally beneficial bacteria, the effects on human life could potentially be fatal.

Bacterial flora balance can increase or decrease due to many factors. Health is a major factor and can change as one becomes older and disease becomes prevalent. If antibiotics are needed, the proper use of antibiotics is key. If antibiotics are used when they are not needed, bacteria could become resistant and harder to treat. Antibiotic resistance is fast becoming a major problem worldwide due to the misuse of antibiotics when they are not needed or having an antibiotic prescribed when a viral infection is diagnosed. Bacteria and viruses are two completely different life forms which require different types of drugs in order to attack and kill them. Antibiotics will not attack viruses but instead will attack the bacteria that is it specified to kill and leave an unbalanced bacterial flora which could cause disease. Other factors include diet, hormonal state and even personal hygiene. Finally, genetic factors can have an effect on the rise and fall of bacterial levels.

Life in general is based on very fine balance in many respects from bacterial levels, to pH (Acid-Base balance). As illustrated in this article, having the right balance of beneficial bacteria has a major role in assisting us in maintaining our health. Bacteria are versatile organisms that reproduce quickly, adapt and evolve far faster than most other living species on earth. We benefit from that versatility when it comes to the role that bacteria play in our body’s defense and digestion. Unfortunately we succumb to that same versatility when we are infected by bacteria. So now, think of bacteria as a frienemy, it can be good at times or it can be bad.


An Introduction to Probiotics. National Center for Complementary and Alternative Medicine. Website accessed August 30, 2009.


One comment

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