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Related: go to: Good bacteria in food go to: Pathogenic bacteria

Bacteria are needed for life


Most people associate bacteria with the three D's: Dirt, Disease and Death. But if you thought life would be safer without bacteria, you're wrong. Life evolved from, and with, bacteria, and all higher animals are dependent on bacteria. Read in our exhibit on Evolutionhow important bacteria were in the formation of life on Earth. We live in close association with billions of bacteria. They are at the least harmless, and in some cases needed for health. Let's have a look here at the good guys. The bad ones, those that cause bacterial infections and make us ill, are treated in our exhibit on Pathogenic bacteria.

Commensals

The external and internal surfaces of our body, eg. skin, mouth, and gut, are covered with bacteria. Have a look what bacteria live where in and on our body (Source: Southern Illinois Uni Carbondale). These microorganisms are provided with a nice place to live, with a good supply of food and a more or less constant temperature. In return, they compete with pathogenic bacteria, and in this way they form a protection against disease. Since the host and the bacteria both gain from this peaceful living together, we call this commensialism. The normal microflora of our surfaces are called commensals. We are dependent on our commensals in other ways as well: they help us digest our food and produce vital vitamins. Insects that can live on wood can do so because their commensals can digest cellulose, the building block of plant cells. Cows can eat grass because of their commensals. That's why we can't live on the diet of herbivores: we lack the right bacteria. Learn more about Microorganisms in health and disease (Source: Uni Leeds).

When your gut is fully loaded with 'good' bacteria, they provide a degree of protection against pathogens that have to compete for food. This is how 'probiotic' food is designed, for instance lactobacilli in yoghurts. One would need to eat such foods on a daily basis to be effective; fortunately our body also has other ways to combat pathogens, as you can find out in our subject catagory how we fight bacteria. If your gut commensals are decreased in numbers, for instance due to a course of antibiotics that was needed to combat an infection, diarrhea may be the result. That is what happens if we destroy our commensals.

Symbionts

There are many examples of bacteria and hosts that live together with mutual interest. The term symbiosis is used when two species live closely together and are completely dependent of each other. For instance, certain plants produce root nodules in which bacteria live. The bacteria produce vital nutrients for the plant, and receive food in return. Both plant and bacteria cannot grow without each other. Maybe the application of such plant-growth-promoting Rhizobacteria can replace the use of methylbromide, a pesticide, in argiculture (Source: ARS/USDA). This is an example of applied bacteriology, a division of bacteriology that is described in a separate exhibit.

Other examples of symbiosis with bacteria are


The content of this page is copyright of the Virtual Museum of Bacteria and was written by Dr. T. M. Wassenaar (curator), with support of the Foundation for Bacteriology.

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Page last modified: 09 Mar 2007

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