Foundations In Microbiology 10Th Edition By Kathleen Park Talaro – Test Bank

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Foundations In Microbiology 10Th Edition By Kathleen Park Talaro – Test Bank

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Clinical Connections:  The Cell Wall and Infections

To understand this, we must compare the basic structure of the cell walls of gram positive vs gram negative bacteria.  Gram positive cell walls have an open matrix that allows the ready entry of the penicillin directly into the peptidoglycan that makes up the major component.  The penicillin interferes with the construction of the cross bridges and prevents synthesis of an intact wall, which makes the cells very sensitive to lysis.  Gram negative cells have an outer membrane that is rather impermeable.  Only chemicals that can pass through the porin proteins of the outer membrane can enter the rest of the cell wall where the peptidoglycan is.  So the barrier of the outer membrane keeps penicillin from entering and having its effect on the cell wall of gram negatives.

Clinical Connections:  The Impact of Endospores

From its name, you can expect that Clostridium difficile is an endospore-producer.  It is an occasional resident of the large intestine of humans.  It causes severe disease in susceptible patients who have been administered broad-spectrum antibiotics.  The antibiotics disrupt the balance of intestinal microbiota, leaving C. difficile as an invasive pathogen.  It causes colitis and severe diarrhea and can be readily spread to other patients.    Characteristics that contribute to its medical impact are that its spores are difficult to destroy by regular disinfection, it is very drug resistant, and it flourishes in anaerobic habitats such as the large intestine.

4.1 The Secret World of Microbes:  Redefining Bacterial Size

The adaptations that a large bacterium such as Thiomargarita must make is first, to evolve a way to get nutrients into its cells from the surrounding environment.  It has a very large volume and a relatively small surface area, so it must have a storage capacity for its main source of nutrients, which are sulfur and nitrogenous compounds stored in large inclusions within the cell body.   It must also have a way of of transporting proteins and other substances from the ribosomes to the regions in the cell where they are used in synthesis and metabolism.  Diffusion alone may not be able to account for rapid transport of molecules. Since oxygen gas would be at low levels in the ocean sediments, they have developed an anaerobic metabolism that does not require O₂.  It may compensate for its large size by forming biofilms that facilitate sharing nutrients and coordinate the actions of the entire colony.