Importance of determining bacterial metabolism of carbohydrates is oxidative ot fermentive
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Explain why it is important to know if a bacteria does Aerobic respiration, Anaerobic respiration and/or Fermentation.
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catabolism: does not require oxygen, but may occur in its presence (anaerobic; fermentation) INTRODUCTION In order for bacteria to survive and flourish, they must have a source of energy. Heterotrophic bacteria obtain their energy by means of either respiration or fermentation, with carbohydrates representing the most common macromolecule source. In respiration, glucose is converted into ATP via three stages: glycolysis, citric acid cycle, and oxidative phosphorylation, resulting in an inorganic molecule serving as the final electron acceptor. In contrast to respiration, fermentation is the metabolic process in which glucose acts as an electron donor and one or more of its organic products acts as the final electron acceptors. Although glucose is the most common monosaccharide utilized, some bacteria possess the genetic blueprints for the enzymatic machinery to utilize other sugars as the energy source: commonly used include sucrose, lactose, mannitol, and mannose. The capacity to utilize sugars other than glucose provide bacteria the flexibility to survive periods where a common energy source is absent or diminished. The ability of microorganisms to utilize or ferment different sugars, and the type of products formed when the sugars are fermented are very useful characteristics for identification. The range of metabolic capabilities that bacteria exhibit is very large, explaining in part why these organisms can be found in nearly every environmental habitat. Not only are bacteria capable of obtaining energy by a variety of pathways, some of which are unique to bacteria, but they are capable of utilizing a large number of different metabolites. The tests performed in this lab are useful to determine different mechanisms of carbohydrate consumption for growth and provide diagnostic features that can be used to differentiate between unknown organisms. Fermentation tests (with Durham tubes): In this test, phenol red broth is used, with different sugars added. Phenol red is a pH indicator used to determine if acidic products are made, such as occurs during fermentation of sugar (yellow below pH 5.2, begins to turn red at 6.8, completely changed to red at pH 8.4). Should fermentation occur, the medium will turn from red to yellow because of the production of acidic fermentation products. There will also be a smaller tube (Durham) inside for the entrapment of gas bubbles, should any gas be produced. If the bacteria do not utilize the sugar, they will often use the amino acids contained in the medium. When amino acids are used, ammonia is produced as a by-product, causing the pH of the medium to rise (the color will turn pink) becoming more alkaline. If the sugar is used oxidatively (respiration), there will be little, if any, color change. A summary of the interpretation and appearance follows: Fermentation, acid, gas -> yellow media, bubble in Durham tube
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