Antibiotics-Summative Practical 4 23042018.docx -...

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FOUNDATION YEARBIOLOGY UNIT 1Investigating AntibioticEffectiveness on twoSpecies of BacteriaBackgroundAntibiotics are capable of destroying orweakening certain microorganisms,especiallybacteria, whichcauseinfections or infectious diseases.Antibiotics are usually produced by orsynthesized from other microorganisms,such as moulds. They inhibit pathogensby interfering with essential intracellularprocesses, including the synthesis ofbacterial proteins. Antibiotics do not killviruses and are not effective in treatingviral infections. Antibiotics were oncethought a nearly perfect drug forcombating bacteria. Bacteria aregrouped in a number of different ways.Most bacteria are of one of three typicalshapes: rod- shaped (bacillus), round(coccus, e.g., streptococcus), and spiral(spirillum). Another group, vibrios,appears as incomplete spirals. Thecytoplasm and plasma membrane ofmost bacterial cells are surrounded by acell wall. The further classification ofbacteria is based on cell wallcharacteristics. They can also becharacterized by their patterns ofgrowth, such as the chains formedby streptococci.Some bacteria can function only inthe presence of oxygen. Otherscannot grow in the presence of freeoxygen but obtain oxygen fromcompounds. Facultative anaerobescan grow with or without freeoxygen; obligate anaerobes arepoisoned by oxygenThinking of the size and diversity ofthe Bacteria kingdom, we see thatbacteria are too diverse for any onedrug to kill them all. Someantibiotics come close, though.These are called “broad spectrum”antibiotics. Other kinds of antibiotics

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