Topsoil in its natural state contains many types of bacteria. Many of these bacteria serve important functions in soil health and the environmental cycling of nutrients, such as nitrogen. Although bacteria often have a positive role in the environment, in the wrong places they can cause human health problems, such as bacterial infections. Because of potential problems with infections, fully cooking certain foods, like meats, and thoroughly washing other foods, like fruits and vegetables, is very important.
Bacteria in the citrobacter species include Citrobacter freundii, a rod-shaped bacteria that ranges from 1 to 5 micrometers long. Some citrobacter are non-mobile, but many use multiple flagella, or "tails," for propulsion. Citrobacter lives in topsoil and other places, including soil, sewage, food, and in both animal and human intestines. Citrobacter can cause infections of the lungs and respiratory organs, urinary tract, and in some cases the blood. Although infectious in people, it has a positive impact on the nitrogen cycle and is very important to the health of the environment.
Enterobacter is a class of bacteria that is infectious in people. This bacteria is rod shaped and uses flagella to move. Enterobacter is found in many places, including in soil or on human skin. It is also found in water, sewage and in both human and animal intestinal tracts. Some kinds of these bacteria live naturally on cucumber and radish skins. They are sometimes also found in peas, soybeans, sunflowers and sweet corn kernels. Even though these bacteria naturally exist on human skin, in some cases they can reproduce enough to become an infection. In addition to skin infections, enterobacter can be responsible for a number of infections, including soft tissue, respiratory, urinary tract and abdominal infections.
E. coli is a class of bacteria that originates in animal fecal material. Through the use of these materials as fertilizer, E. coli is transferred to topsoil. The E. coli bacteria are rod-shaped bacteria that have evolved and mutated into hundreds of strains. Although many of these strains are not harmful, a few are sometimes fatal to humans. E. coli does not survive heat well and as such is easily killed by boiling or thorough cooking. E. coli is well known due to a number of high profile cases of bacteria-based food poisoning linked to the bacteria.