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BISC209/F13: Lab7: Difference between revisions
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→McFarland Turbidity Standards
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==McFarland Turbidity Standards== | ==McFarland Turbidity Standards== | ||
1) You will use the fresh broth culture of each of your isolates that you prepared prior to lab for both the antibiotic and interactions protocols. We want to apply relatively the same number of organisms in each procedure so we will use McFarland Standard 5 to | 1) You will use the fresh broth culture of each of your isolates that you prepared prior to lab for both the antibiotic and interactions protocols. We want to apply relatively the same number of organisms in each procedure so we will use McFarland Standard 5 to "correct" turbidity. <BR> | ||
2) Although cell density can be measured more accurately using a spectrophotometer to measure optical density (OD) at 600nm, we will use a quicker method that will work well enough for our purposes. We will use a McFarland 0.5 standard; the 0.5 refers to the approximate concentration of organisms in solutions which is 1.5X10<sup>8</sup> cfu/mL for the 0.5 standard. Other common standards are shown in the table below. <BR> | 2) Although cell density can be measured more accurately using a spectrophotometer to measure optical density (OD) at 600nm, we will use a quicker method that will work well enough for our purposes. We will use a McFarland 0.5 standard; the 0.5 refers to the approximate concentration of organisms in solutions which is 1.5X10<sup>8</sup> cfu/mL for the 0.5 standard. Other common standards are shown in the table below. <BR> | ||
