Aseptic Technique 2

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Biological Concepts
Microorganisms and Biotechnology
Use of Aseptic Technique

Introduction
Microorganisms (microbes) such as prokaryotes are the oldest life form that we know. Various forms have been discovered, not only to survive, but to thrive in the most hostile and extreme of environments and have been named extremophiles and various types of microbes are found in every niche of ecology. Due to their resilience and success at sustaining their existence, it has proven to be quite difficult to control their reproduction where they are harmful. (Toole & Toole, 1995). Some types are symbiotic and are crucial to the survival of other organisms e.g. the dinoflagellates found living amongst the polyps of reef-inhabiting coral. (Dorit, Walker & Barnes, 1991). Others exist in their own right, but are harmless and many are useful e.g. yeast, used in the production of beer and baking or enzymes used in the food industry, which are produced from microorganisms. Pathogens however can cause damage or even bring about death to other organisms and these are the microbes that humans have battled to control over many years with varying degrees of success. (Toole & Toole, 1995) Microscopic parasites such as Nematodes (roundworms) are diverse. Treatments for such infestations target inhibition of growth or reproduction. If an area needs to be treated to prevent the infection of another organism disinfectants may be used. They work by inhibiting the growth or destroying the microbes whilst in their vegetative state. Some disinfectants (e.g. alcohols) disrupt the integrity of the lipid content within the membranes of the cells. This eventually leads to the rupture of the cell. Disinfectants that are halogen based (e.g. chlorine) denature the proteins in the cells, thereby killing the microbes. (Toole & Toole, 1995). Viruses, unlike bacteria, are obligate intracellular parasites that can only reproduce after infecting host cells. Antiviral development is a relatively new and is currently used to ‘manage’ viral infections and stop them spreading, as opposed to curing them. Due to the reproductive requirements of a virus, an antivirus works on either preventing the virus from entering a host cell, or, in the case of where cell infection has already occurred, the antiviral works by preventing viral offspring from budding out of the host cell to spread infection. The antivirals do this by binding to the glycoprotein’s of the virus envelope, preventing it from binding to specific receptor molecules on the host cell, fusing with the cell and then entering it. Due to the antiviral binding to the glycoprotein’s, this also prevents the successful reproduction of the viral offspring, as the glycoprotein’s cannot be replicated by the host cell for the budding cycle to occur and the virus cannot be released, preventing the infection spreading. (Campbell, 1991) Antifungals are agents which target fungal cells. Fungal cells have many similarities to mammalian cells as they are both are eukaryotes with DNA organized into chromosomes within the cell nucleus and have distinct cytoplasmic organelles. This homology to mammalian cells also extends to biosynthetic pathways, where fungi share similar mechanisms for DNA replication and protein synthesis. Due to this there are many side effects with this type of treatment. Polyene antifungals are used to avoid causing cell damage to the patient. Polyene antifungals such as amphotericin B bind to ergosterol in the fungal cell membrane (the mammalian cell membrane contains primarily cholesterol not ergosterol). This binding results in depolarization of the membrane, changing the transition temperature of the membrane, placing the membrane in a less fluid, more crystalline state, resulting in formation of pores and leakage of monovalent ions, eventually leading to cell death. (Bammert & Fostel 2000). Antibiotics are the most widely used treatment for infections caused by...
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