front 1 _______ are the primary vehicle responsible for the transmission of microbial diseases of the gastrointestinal system | back 1 food products |
front 2 heterotrophic plate count | back 2 used to determine the number of viable bacteria in a food sample. the larger the count, the greater the likelihood that specific pathogens capable of causing disease will be present and also that the food will spoil. |
front 3 Normally, raw hamburger should not contain over _____ bacteria per gram | back 3 10^6 |
front 4 One of the limitations of the heterotrophic plate count | back 4 only bacteria capable of growing in the culture medium under the environmental conditions provided will be counted |
front 5 heterotrophic | back 5 requiring organic carbon |
front 6 standard plate count | back 6 a procedure that allows microbiologists to estimate the population density in a liquid sample by plating a very dilute portion of that sample and counting the number of colonies it produces |
front 7 serial dilution | back 7 a series of controlled transfers down a line of dilution blanks. the series begins with a sample containing an unknown concentration of cells (density) and ends with a very dilute mixture containing only a few cells. |
front 8 dilution blanks | back 8 tubes containing a known volume of sterile diluent - water, saline, or buffer |
front 9 If a dilution is 10^-4, the proportion of the original sample inside the tube would be what? | back 9 1/10000th of the total volume inside. |
front 10 When 0.1 mL of a 10^-4 solution is transferred to a plate, what is the volume of the sample in the plate? | back 10 0.1 mL x 10^-4 = 10^-5 mL |
front 11 countable plate | back 11 contains between 30-300 colonies |
front 12 Plates with fewer than 30 colonies are ___ | back 12 TFTC (too few to count) |
front 13 Plates with more than 300 colonies are ____ | back 13 TMTC (too many to count) |
front 14 Dilutions can be calculated using the following formula | back 14 V1D1 = V2D2 |
front 15 V1 and D1 are what? | back 15 The volume and dilution of the concentrated broth |
front 16 V2 and D2 are what? | back 16 the volume and dilution of the completed dilution |
front 17 Undiluted samples are always expressed as ____ | back 17 1 |
front 18 To calculate the dilution of a 1 mL sample transferred to 9 mL of dilutent, the permuted formula would be: | back 18 D2 = (V1D1/V2) = [(1.0 mL x 1) / 10 mL] = (1/10) = 10^-1 |
front 19 Formula for calculating original cell density (OCD) | back 19 OCD = CFU / (D x V)
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front 20 Colony Forming Unit (CFU) | back 20 the number of colonies that develop on the plate |
front 21 Why is CFU the preferred term? | back 21 Because colonies could develop from single cells or from groups of cells, depending on the typical cellular arrangement of the organism. |
front 22 Original sample volume | back 22 density and volume from the OCD = CFU / (D x V)
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front 23 When is the sample volume written on the plate? | back 23 at the time of inoculation |
front 24 viable count | back 24 provides an estimate of actual living cells in the sample |
front 25 What bacteria will we be using in this lab? | back 25 Escherichia coli (E. coli) |
front 26 In this lab we will inoculate the plates using what technique? | back 26 spread plate technique |
front 27 We will count bacterial colonies using what? | back 27 colony counter |