BIOL241 Study Guide - Final Guide: Fecal Coliform, Citrobacter Freundii, Enterobacter Aerogenes
24 Nov 2016
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G +ve, nonmotile, microaerophilic or anaerobic rods or cocci lactobacillus, Advantages: good for high numbers, rapid results, individuals and clumps can be counted, morphological types, slides kept as permanent record. Disadvantages: not for low count, dead cells cant be distinguished, tedious, debris can be confused. Slide over boiling water to heat fix. 0. 005 ml of milk sample in center of slide. Calculate mf by using a stage micrometer to measure the diameter. [1 / (area / 100)] / portion of ml that was spread over area. [1 cm2 / ( r2 mm2 / 100 cm2)] / 0. 005 ml/cm2 = # fields in 1 cm2 (mf) cells / ml = avg # cells / field x mf. Raw milk and post-date pasteurized have a higher number of microorganisms than fresh pasteurized. Official method for determining sanitary quality of milk. Serial dilutions either spread plate or pour plate.
