BIOL241 Study Guide - Fecal Coliform, Coliform Bacteria, Enterobacter Aerogenes
25 Mar 2014
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Experiment 2: standard plate count of milk. Experiment 3: microbial analysis of cheese. Biol 241l introduction to the microbial world. Experiment 1: direct microscopic count of microorganisms in milk. Calibration of microscope: microscope factor. Microbial population of milk is typically composed of gram- positive, non- motile, microaerophilic or anaerobic rods and cocci. Lactobacillus, micrococcus and steptococcus are typically represented. Milk samples vortexed to disperse organisms and break up clumps of bacteria. Slidebrite is used to remove fat globules. Slide stained with methylene blue, decolourized with ethanol. Microscope factor (mf): relationship of the field to a ml. Measure the diameter of the microscope field each space = 0. 01mm. Use r2 to calculate the area in mm2. Convert this area to cm2 by dividing by 100. Divide 1 cm2 by the area of the field to calculate the number of fields/cm2. Mf = fields/cm2 / 0. 005 ml/cm2. Each colony is assumed to have arisen from an individual bacterial cell.
