Unknown Bacteria

Topics: Staining, Gram-positive bacteria, Microbiology Pages: 5 (1832 words) Published: November 14, 2012
Biological organisms are classified uniformly in order to easily categorize and identify organisms. This classification, or taxonomy, uses the genus name followed by the species name, in Latin. By having a universal method of identifying bacteria allows for all scientists from any part of the world to identify the same species in an identical manner allowing for a precise of classification. Bacteria are distributed throughout the world in almost every conceivable habit. Bacteria are unicellular microorganisms, with variable shapes and nutritional needs. They lack a distinct nucleus and occur singly or in chains or clusters and form distinct colonies. Bacteria are classified on the basis of many characteristics. Morphological and physiological features such as cell shape, motility, formation of spores and other distinguishable structures, and reaction to Gram stain is a good start in identifying bacteria. Other staining techniques such as Acid Fast stain are also useful in determining species. More important in identification of a genus and species of bacteria are biological tests, including the determination of the types of nutrients a cell can use, the products of its metabolism, and the response to specific chemicals. Other factors that can assist in identification of bacteria are their ecological habitats and more advanced methods such as genetic and molecular composition. Using various techniques one is able to distinguish and ultimately assign then genus and species of the unknown bacteria. Methods:

Gram Staining: The Gram stain separates bacteria in two distinct classes and is also useful in distinguishing morphology. Through this technique one is able to identify bacteria as either gram positive or gram negative. The gram-negative bacteria have thin peptidoglycan layers that do not hold the primary stain, rather the secondary stain, staining red in color. On the contrary, gram-positive bacteria have a teiochoic acid shield and a thick peptidoglycan layer which hold in the primary stain, staining violet in color. Through an enhanced observation of the morphology of the bacteria’s cell shape is a cocci (spherical), bacillus (rod), or spirilla (spiral). Catalase test: During Aerobic respiration the formation of hydrogen peroxide can form by the reactivity of hydrogen and oxygen. This product is lethal to most cells unless a Catalase enzyme is present to break down the hydrogen peroxide. Most aerobic bacteria have this enzyme while anaerobic are deficient, therefore using other compounds or final electron acceptors. In this test we are exposing the bacteria to hydrogen peroxide. If the bacteria are aerobic, it will have the Catalase enzyme and bubbles should form, signifying the bacteria’s ability to break down the hydrogen peroxide into water and oxygen. If bubbles do not form it is clear indication that the bacteria is anaerobic and does not have the ability to breakdown the hydrogen peroxide into water and oxygen. If bubbles do not form it is a clear indication that the bacteria is anaerobic and does not have the ability to break down the hydrogen peroxide. Glucose Fermentation: By using fermentation tubes one is able to indicate whether the bacteria ferments glucose to drive ATP synthesis or not. The end produces of glucose fermentation is hydrogen gas, carbon dioxide and organic acids. The fermentation tubes is used to detect if these end products are present. These tubes are to be capped and contain carbohydrates, peptone, phenol-red (acid-base indicator) and an inverted smaller tube. Glucose fermentation that results in an acid end product turns the phenol-red indicator yellow due to decreased pH levels, designating glucose fermentation. If gas is present due to fermentation of glucose, some of the gas will be trapped in the inverted tube in the fermentation tubes. Yet after a prolonged period of time there may be an exhaust of the carbohydrate supply causing the bacteria to begin growing...
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