BIOL241 Study Guide - Midterm Guide: Rhizobia, Ammonium Iron(Ii) Sulfate, Arabitol
17 Apr 2015
School
Department
Course
Professor
Document Summary
Direct microscope factor calculation area of field ( r ) convert from mm to. Clara tsui cm : # of fields in 1 cm /area = # of fields, microscope factor = # of fields / vol. of milk over 1 cm , (in our experiment it was 0. 01ml/cm ) Fresh pasteurized milk had the lowest count; past-date is next, then raw milk has most. Standard plate count colonies formed = # of viable microorganisms (only the mos capable of growing on those nutrients/conditions) Mea- selective (mold/fungi can grow detect cheese mold) Emb detect coliforms that cause gas defects in cheese. Differential e. coli green metallic sheen around dark purple colonies. Selective methylene blue and eosin inhibits growth of gram-positive organisms (ie. streptococcus, staphylococcus) Streptococcus and lactobacillus are lactic-acid producing bacteria (initiate cheese- making process) Defect: clostridium/e. coli/enterobacter aerogenes form gas, or geotrichum, Salmonella not usually found in food products, so enrichment step is necessary; staphylococci are abundant.
