Bacteria & History and ecology

The word ‘bacteria’ is normally associated with disease-causing organisms, like the Streptococcus bacteria. While there are a considerable number of pathogenic bacteria that are notorious for such diseases as cholera, tuberculosis, and gonorrhea, such disease-causing species are a comparatively tiny fraction of the bacteria as a whole. There are approximately five nonillion (5? 1030) bacteria in the world. Bacteria are so widespread that it is possible only to make the most general statements about their life history and ecology (Berkeley Free Clinic, 1).

There are bacteria that plays important role in the global ecosystem. They may be found on the tops of mountains, the bottom of the deepest oceans, in the guts of animals, and even in the frozen rocks and ice of Antarctica. One feature that has enabled them to spread so far, and last so long is their ability to go dormant for an extended period. There are specific methods in order to study and observe bacteria because they are not visible to the naked eye. Even with the use of microscope they are very difficult to spot without adding some stains that would render them visible.

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DETAILS Properties Bacteria are prokaryotic (no membrane-enclosed nucleus) that do not contain mitochondria or chloroplasts. They have single chromosome that are composed of close circle of double-stranded DNA with no associated histones. If flagella are present, they are made of a single filament of the protein flagellin; there are none of the "9+2" tubulin-containing microtubules of the eukaryotes (Users. rcn. com, 1). Their ribosomes differ from those of the eukaryotes. Bacteria have a rigid cell wall made of peptidoglycan that allows them to survive at long periods of time.

They do not perform mitosis and mostly reproduce through asexual reproduction. Any form of sexual reproduction varies differently from the eukaryotes because they do not perform meiosis. The plasma membrane is a phospholipid bilayer but contains no cholesterol or other steroids (Users. rcn. com, 1). Most of bacteria form a single spore when their food supply runs low. This is the reason why pathogenic bacteria become infectious at the later part of the attack. Most of the water is removed from the spore and metabolism ceases.

Spores are so resistant to adverse conditions of dryness and temperature that they may remain viable even after 50 years of dormancy (Users. rcn. com, 1). Environmental and Nutritive Requirements Most bacteria can be classified according to their response to oxygen. These are consist of three distinct group, Aerobic bacteria which thrives in the presence of oxygen, Anaerobic which cannot tolerate gaseous oxygen, and facultative anaerobes which prefer growing in the presence of oxygen but are able to survive without it. Aerobic bacteria require oxygen for their continued growth and existence.

On the other hand anaerobic cannot survive in the presence of gaseous oxygen. These bacteria live in deep underwater sediments, or in oxygen deprived environment such as those that cause bacterial food poisoning. Bacteria also differ in the mode and source of their energy. There are Heterotrophs that derive energy from breaking down complex organic compounds that they must take in from the environment. This includes saprobic bacteria found in decaying material, as well as those that rely on fermentation or respiration.

The other group, the autotrophs, fix carbon dioxide to make their own food source; this may be fueled by light energy (photoautotrophic), or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic) (Berkeley Free Clinic, 2). Chemoautotrophs are uncommon while photoautotrophs are more common and quite diverse. One particular bacteria offers a very interesting behavior because they use hydrogen sulfide as hydrogen donor, instead of water like most other photosynthetic organisms, including cyanobacteria.

There are green sulfur bacteria and purple sulfur bacteria, Other Bacteria include the cyanobacteria, and purple nonsulfur bacteria. Role in the Global Ecosystem Bacteria play a very important role in maintaining the balance of our ecosystem. Through their ceaseless labor, they cycle nutrients such as carbon, nitrogen, and sulfur. For example without bacteria to decompose rotten objects, our CO2 would have been depleted and all our plants would have ceased to exist. The process of decomposition releases nutrients back into the environment for plants and other living organisms.

Bacteria also cycle nitrogen in the soil. Nitrogen is important for plants health and growth. Without these cycling processes all our plants would die and then humanity would have ran out of food. Gram Stain Bacteria happens to have a refractive index similar to water, therefore they are very difficult to spot from an aqueous sample. To solve this problem, biological stains are added so that microorganisms can be visualized. Stains are classified as either simple or differential.

Simple stains impart the same color to all structures whereas differential stains contain more than one dye and impart different colors to various structures(Delost, 39). One very important method is the Gram Stain, which was first introduced by Hans Christian Gram in the late 1800s. It has been modified and adjusted numerous times. The Gram stain will differentiate gram-positive bacteria from gram-negative bacteria (Delost, 39). Gram stain is one form of a differential stain that is widely even in the methods.

It consists of several reagents such as crystal violet, Gram’s iodine, ethyl alcohol or acetone, and safranin O or carbulfuchsin. Bibliography Unknown. (2000). Bacteria: Life History and Ecology. Retrieved on February 18, 2007 from the Berkeley Free Clinic website: http://www. ucmp. berkeley. edu/bacteria/bacterialh. html Unkown. (2006). Bacteria. Retrieved on February 18, 2007 from the Users. rcn. com website: http://users. rcn. com/jkimball. ma. ultranet/BiologyPages/E/Eubacteria. Delost, M. Introduction to Diagnostic Microbiology. (1997). Harcourt Brace & Company Asia Pte Ltd. .

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