Phyiscal and chemical control of growth and viabilty - Essay Example

Physical and chemical control of growth and viability Lecturer This paper seeks to present and discuss the similarities and differences in the microbial metabolic and environmental requirements for growth. Emphasis and focus will be on the effect of environmental factors on growth, and the growth criteria for the subject microorganisms. Microorganism is characterized by their ability to multiply, grow and make organism population. A major result of microbial metabolism is the increase in the cell size.

There are various requirements of microbial growth ranging from physical, chemical, metabolic and environmental. However, this paper will focus on environmental microbial growth requirements (Todar, 2008).Environmental requirements are particularly physical conditions that affect the amount and type of microbial growth. For example, activities of enzymes are dependent on environmental temperature. Microorganisms are also classified into groups based on their preferred environmental temperature.

For example: thermophilic organisms, thermophiles prefer very high temperatures of above 400; mesophilic organisms, mesophiles grow well in temperatures of 200 to 400; while psychrophiles, psychrophilic organisms prefer relatively low temperatures. However, a range of maximum or minimum growth temperature exists for every individual species. The best growth occurs at optimum growth temperature (Singh, 2010).Another environmental requirement for microbial growth is the extent of alkalinity or acidity of the habitat, also referred to as a pH solution.

Most of the microorganisms prefer an optimum pH of between 6.5 and 7.5. The tissues of the human body is between 7.0 and 7.2, therefore neutrophilic microorganisms often grow in the body very well. Other microorganisms such as those in yoghut and sauerkraut which are acidophilic grow well in acidic environment of below 6.0, for example yeast and molds. Microbial growth also does well where osmotic pressure is idyllic. In most cases, the concentration of salt in microbial cytoplasm is around one percent.

Where there is one percent concentration of salt in the environment, the osmotic pressure is at optimum. In case the salt concentration rise in the external environment, water will definitely flow out of the cytoplasm through osmosis via cell membrane to the environment resulting into shrinking of the microorganism, and ultimately death. In contrary, where external water has minimal salt, water flows into the cytoplasm through the cell membrane resulting into cell swelling and ultimately burst.

Conclusively, microorganisms living in marine environment are able to tolerate high concentrations of salt. These are referred to as halophilic microorganisms, for example dinoflagellates and diatoms (Hooker, 2007).Microbial growth is also affected by environmental oxygen requirements. Most microorganisms demonstrate a great variation deal in their requisites of gaseous oxygen. Microorganisms have been classified depending on the need of oxygen. for example, obligate aerobes, are those organisms that only grow in the presence of oxygen.

such microorganisms derive their energy from aerobic respiration; microaerophiles, are those organisms requiring low oxygen concentrations of between 2% and 10% for growth. Such microorganisms show an inhibited growth with higher oxygen concentrations; obligate anaerobes, these microorganisms grow well in the absence of oxygen only. The presence of oxygen often inhibits or kills the organisms. Their energy is obtained from fermentation or anaerobic respiration; aerotolerant anaerobes, such microorganisms do not use oxygen in energy transformation, but grow well in its presence.

They derive their energy through fermentation, hence referred to as obligate fermenters; finally, we have facultative anaerobes consisting of microorganisms growing well with or without oxygen, however, they do better in the presence of oxygen (Kaiser, 2010).ReferencesHooker, M. (2007).Clostridium Difficile. Clinical Journal of Oncology Nursing, 11, 801-804. Kaiser, G. (2010) The Grapes of Staph Doc Kaisers Microbiology Website. Retrieved December3, 2012 from http://student.ccbcmd.edu/~gkaiser/welcome.

htmlSingh, Uma Shankar Kapoor, Kiran. (2010). Introductory Microbiology, Jaipur: Global Media.Todar, K. (2008). Overview of Bacteriology. Retrieved December 3, 2012 fromhttp://textbookofbacteriology.net/bacteriology.html