Aerobic Versus Anaerobic Bacteria and their Examples

Anaerobic and aerobic bacteria in liquid culture

Anaerobic and aerobic bacteria in liquid culture (Wikipedia)

There are different ways of classifying bacteria; one of which is according to their ability to use oxygen. Aerobic bacteria use oxygen for cellular respiration while anaerobic bacteria don’t. Aerobic bacteria are those that can survive when oxygen is present, while anaerobic bacteria cannot (Jilani 2010).

Aerobes can detoxify oxygen while anaerobes do not have this ability. Oxygen is toxic to bacteria but aerobes use certain enzymes such as catalase and superoxide to get rid of oxygen and turn it into a substance that is not harmful to them. In environments where oxygen is not available, anaerobic bacteria can still exist, unlike aerobic bacteria. This means that anaerobes can cause infection in parts of the human body where there is a depleted supply of oxygen such as in the area from the stomach up to the rectum. While anaerobic bacteria cannot produce much energy through fermentation, aerobes are capable of producing more energy (Naik, 2010).

Aerobic Bacteria

When a bacterium absolutely requires oxygen for their reproduction, growth and survival, they are considered to be obligate aerobes. However, there are also some species that require only a very low concentration of oxygen. These organisms are called microaerophiles (Sandhyarani, 2011).

It is very easy to isolate aerobes and microaerophiles in the laboratory. Since these bacteria need oxygen, they grow on the top surface of liquid media and do not require special equipment for cultivation. All you need is an incubator that is set to the temperature at which the organisms grow optimally. Examples of aerobes and microaerophiles include Mycobacterium tuberculosis, Lactobacillus and Nocardia(Sandhyarani, 2011).

M. tuberculosis is the causative agent of tuberculosis. It is an obligate aerobe that is rod shaped and has a waxy layer in its cell wall. Since it needs oxygen for survival, it invades the lungs of mammals. Nocardia is also another group of bacteria that belong to obligate aerobes. With more than 80 species, some of them are pathogenic while others are not. They are usually found in the oral cavity as normal flora but are considered as pathogens when they invade the lungs and cause an infection called nocardiosis (Sandhyarani, 2011). An example of a microaerophilicorganism is C. jejuni. It only requires about 3 to 5% oxygen for its growth. When this limit is exceeded, it renders stress to the bacteria. It is one of the leading causes of food-borne illness in the United States (MicrobeWiki).

Anaerobic Bacteria

Anaerobes are bacteria that are able to survive without oxygen. They can be further classified into obligate anaerobes, aerotolerant anaerobes and facultative anaerobes. Obligate anaerobes cannot withstand the presence of oxygen. On the other hand,aerotolerant anaerobes cannot use oxygen for respiration but can survive despite its presence. Facultative anaerobes are bacteria that can grow without oxygen and can use oxygen for respiration. E. coli, Bacteroidesand Clostridium are examples of anaerobic bacteria (Alphonse, 2010).

C. botulinumis a gram positive, obligate anaerobe. It produces the world’s most potent toxin and is usually found in meat products that are not cooked or handled properly. An example of an aerotolerant anaerobe is Bacteroides. It can infect several parts of the body such as the peritoneal cavity and the female urogenital tract. E. coli is one example of a facultative anaerobe. This bacterium is very common and can be found in the gastrointestinal tract of mammals. E. coli can cause infection in the respiratory and urinary tract (Alphonse, 2010).

One important role that oxygen plays for organisms that are able to use it is to help break down food molecules so that energy can be produced for the continued survival of the cell. For organisms that cannot use oxygen, they also have a means by which they produce energy, but they are not as efficient as aerobes (Port, 2009).
Bibliography

  • • Alphonte, M. (2010, February 18). Anaerobic Bacteria. Retrieved November 3, 2011, from Buzzle.com: http://www.buzzle.com/articles/anaerobic-bacteria.html
  • • Jilani. (2010, April 2010). Difference Between.net. Retrieved November 3, 2011, from Difference Between Aerobic and Anaerobic Bacteria: http://www.differencebetween.net/science/difference-between-aerobic-and-anaerobic-bacteria/
  • • MicrobeWiki. (n.d.). Campylobacter jejuni. Retrieved November 3, 2011, from MicrobeWiki: http://microbewiki.kenyon.edu/index.php/Campylobacter_jejuni
  • • Naik, A. (2010, August 16). Aerobic Versus Anaerobic Bacteria. Retrieved November 3, 2011, from Buzzle.com: http://www.buzzle.com/articles/aerobic-vs-anaerobic-bacteria.html
  • • Port, T. (2009, July 15). Difference between Aerobic & Anaerobic Bacteria. Retrieved November 3, 2011, from Microbilogy Suite 101: http://tami-port.suite101.com/difference-between-aerobic–anaerobic-bacteria-a132294
  • • Sandhyarani, N. (2011, September 27). Aerobic Bacteria. Retrieved November 4, 2011, from Buzzle.com: http://www.buzzle.com/articles/aerobic-bacteria.html
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