plaque assay essays

plaque assay essays Title: Exercise Seven Plaque Assay for Determination of Phage Titre One of the most numerous microorganisms known to man is viruses and these acellular agents can infect all types of cellular organisms. Viruses are considered infectious elements that contain a single type of nucleic acid but require a host cells metabolism to replicate. They are typified by both an extracellular state and an intracellular state. (Madigan et al, 2003; Prescott et al, 2002). The classification of viruses can be extended further, by focusing on a specific group known as Bacteriophages. These are viruses that infect bacterial cells and use them as their host. Those viruses that infect Eschericha coli are known as Coliphages and are identified by type numbers ie. T2, T4 and T7. (Prescott et al, 2002; Reddy, 2002). Temperate bacteriophages not only infect bacteria but can also establish a lysogenic relationship rather than immediately lysing their hosts. The DNA of the invading phage has two possible fates: reproduction leading to generation of new phage particles and lysis of the cell or integration into the host chromosome. Here it is replicated passively with the host DNA a process known as lysogeny. Some coliphages (although not exclusively) are temperate bacteriophages. (Lehninger et al, 1992; Madigan Despite the diversity in viral structures, most viruses complete similar stages in the viral lifecycle. Excluding the lysogenic pathway for the moment, a typical viral lifecycle can be categorized into five stages: 2. Penetration: by either the whole virion or just the nucleic acid 3. Synthesis of nucleic acid and proteins: where the hosts metabolism is utilized 4. Assembly: of structural subunits and packaging It should be noted that these are generalized stages and that viruses go about a ...