113lecture1706 - BIOLOGY 113 - MICROBIOLOGY Lecture 17:...

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BIOLOGY 113 - MICROBIOLOGY Lecture 17: Viruses - Characteristics and classification of viruses, growth of viruses in the laboratory Viruses were originally distinguished from other infectious agents by the observations that they were able to pass through filters designed to retain bacteria, and because they are obligatory intracellular parasites, able to reproduce only inside of living cells - Today we know that both of these characteristics are shared by certain small bacteria - A definition of the term "virus" remains difficult; perhaps they can be best compared with other, cellular, living forms by consideration of what they lack (Tortora et al., Table 13.1) = Viruses do not possess ribosomes and thus are unable to carry out independent gene expression = Although some viruses are enclosed in a semipermeable membrane (the viral envelope) , these membranes do not carry out the same functions of transport and energy metabolism as the plasma membranes of cells = What few enzymes a virus may possess are not involved in obtaining metabolic energy - The fact that viruses depend on the metabolism of their host cells for reproduction makes treatment of viral infections difficult = With bacteria, we can use toxic compounds (e.g., antibiotics) that interfere with bacterial metabolism but have no effect on human cells = Most drugs that would interfere with viral multiplication would also interfere with the function of the host cell = There are some drugs, including nucleotide analogs, that target specific features of the metabolism of cells infected with viruses - The host range of a virus is the spectrum of host cells that the virus can infect = Most viruses multiply only in cells of a particular species or limited group of species
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This note was uploaded on 11/24/2011 for the course BIO 113 taught by Professor Staff during the Fall '09 term at Rutgers.

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113lecture1706 - BIOLOGY 113 - MICROBIOLOGY Lecture 17:...

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