Why is it important to complete morphological and cultural characterizations before pursuing physiological testing?
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Morphological and cultural characterization are necessary to help with the preliminary classification. It helps point in the right direction of which tests are appropriate for further identification.
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In regard to taxonomic classification of bacteria, what is the relationship between physiological and genetic differentiation of bacteria?
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Physiology is a display of what proteins and enzymes . they are producing which comes from their genes.
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What is the function of bacterial exoenzymes?
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Exoenzymes are used for the extracellular degradation of macromolecules into smaller molecules that can be taken into the cell as metabolites, nutrient/energy sources.
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Anabolism
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Energy driven synthesis of complex molecules (proteins) from smaller ones
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Catabolism
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Energy releasing degradation of complex molecules into smaller ones
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Fermentation
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Metabolism of sugars in the absence of oxygen
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Respiration
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Metabolism process that does utilize oxygen
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Why is the catalase test useful for the differentiation of staphlococci from streptococci?
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Both are gram positive cocci, but staphlococci are catalase positive and streptococci are catalase negative.
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How are end products of biochemical rxns, often acids or alkalies, typically detected in a culture medium?
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Both are detected with pH indicators, which are colored dyes such as phenol red in the broth or agar that change in response to pH changes.
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Name 2 tests for rxns that produce acid end products
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1. Kligar's Iron Agar
2. Fermentation of carbohydrates (sugars)
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Name 2 tests for rxns that produce alkaline end products
What type of gases can be produced as a result of sugar fermentation?
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CO2 and H2
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How are these gases detected in fermentation rxns?
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Durham tube
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Name a nonfermentative test in which gas production indicates a positive test result
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Nitrate reduction
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The tests for the hydrolysis of starch, casein, and triglycerides are similar in terms of setup. How do the methods for the detection of hydrolysis differ between these 3 tests.
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In the casein test, the hydrolysis of casein in milk shows clear zones of hydrolysis. In the starch test, iodine is needed to show the clear zones of hydrolysis. In the triglyceride test, spirit blue agar, which contains a pH indicator, shows hydrolysis.
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Which test is used to differentiate between fermentative and oxidative metabolism?
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oxidative and fermentative glucose test (o/f)
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For which of the 5 hydrolysis tests would a positive test be expected for: the etiologic agent of acne, Propionibacterium acnes? Explain
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-positive triglyceride hydrolysis test (TAG hydrolysis)
-acne feeds on triglycerides that are present in oil-filled glands
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For which of the 5 hydrolysis tests would a positive test be expected for: the etiologic agent of gastric ulcers, Helicobacter pylori? Why would this activity be advantageous in this environment?
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-positive urea hydrolysis
-it is advantageous to the bacteria because the ammonia produced neutralizes stomach acid so that they can survive and can be pathogenic
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What test do Kligar's iron agar & SIM have in common?
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both test for H2S
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What components of Kligar's iron agar & SIM are included for this test?
Both Kligar's iron agar & SIM are stabbed but for different reasons. Explain.
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SIM tests motility by showing if the substrate moves from the stab. Kligar's iron agar tests for glucose fermentation in the absence of O2 (anaerobic environment)
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What difficulties does one encounter when trying to differentiate bacteria on the basis of physiological tests?
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Many tests need to be performed to differentiate between closely-related bacteria.
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In addition to the morphological, cultural, and physiological tests performed on an unknown, what tests can be conducted to further assist in its identification?
