Chap 5

• Metabolism


  From the Greek term metabolein, meaning change, pertains to all chemical workings of cells
• Physiology


  The branch of biology that deals with the normal functions and activities of life or of living matter
• Enzymes


  The proteins that help speed up metabolism, or the chemical reactions in our bodies
• Catabolism


  Larger molecules are degraded or broken down into smaller molecules, usually with the release of energy (e.g. breakdown of glucose)

  
• Anabolism (biosynthesis)


  Larger molecules are built from smaller ones, which results in the formation of cell structures (e.g. protein synthesis), require energy

  
• Catabolism involves the breakdown of complex organic molecules to extract energy and form simpler end products. Anabolism uses the energy to synthesize necessary macromolecules and cell structures from simple precursors, increasing chemical complexity. The two systems interact in a continuous cycle that maintains the metabolic balance inside cells.

  
• Enzymes for bacterial metabolism

  • Endoenzymes (work within the cells)
  • Exoenzymes (produced inside the cell and then transported to the outside, work outside the cell)

  
• All of this chemistry results in the production of biomolecules and waste, much of which is excreted by the cells into the surrounding environment.
• Detecting and identifying the biochemical products of metabolism provides us with a way to learn more about the physiologic and growth capabilities of bacteria, and also give us a way to differentiate among and/or identify species.

  
• Biochemical tests are used to identify bacterial species by differentiating them on the basis of biochemical activities. The difference in protein and fat metabolism, carbohydrate metabolism, enzyme production, compound utilization ability, etc. are some factors that aid in bacterial identification.

  
• Gram stain is the 1st criteria, biochemical characteristics are the 2nd criteria for determining the identity or taxonomic group of bacteria.

  
• Intemediates or end products of varied metabolic activities can be detected by performing biochemical assays on a bacterial culture. The results of these tests provide a biochemical profile, or "fingerprint" that can be used to classify or even identify the bacterial species.
• The outcomes of laboratory tests can also provide insight into physiology and what is needed to encourage and support bacterial growth.
• Respiration


  The pathway in which organic molecules are sequentially oxidized to strip off electrons, which are then deposited with a final electron acceptor. Along the way, ATP is made.
• Bacterial categories based on oxygen requirement

  • Obligate aerobes
  • Obligate anaerobes
  • Facultative anaerobes
  • Microaerophiles

  
• Fermentation and anaerobic respiration are anaerobic processes - meaning that no oxygen is required for ATP production.
• Catalase test detects the ability of bacteria to produce the enzyme catalase which converts hydrogen peroxide to water and oxygen. All Staph. are catalase positive.
• Oxidase test identifies bacteria that produce cytochrome oxidase or indophenol oxidases, which are redox enzymes in the electron transport system that shuttle electrons to oxygen. If a blue/purple colour appears in 5 to 10 seconds, the microorganisms are oxidase positive.