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BioBuilding: Synthetic Biology for Teachers: Lab 1: Difference between revisions
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BioBuilding: Synthetic Biology for Teachers: Lab 1 (view source)
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[[Image:Note mini.png]]''<font color = red> TEACHERS: ''If you do not have a roller wheel and an incubator, you can prepare these cultures in small erlenmeyer flasks (with stir bars) placed on a stir plate at a slow pace. Cultures are stable and active for a week at least (stored at room temp or in the fridge) but will take considerably longer to start growing on the day you subculture (~3 hours rather than 1).</font><br> | [[Image:Note mini.png]]''<font color = red> TEACHERS: ''If you do not have a roller wheel and an incubator, you can prepare these cultures in small erlenmeyer flasks (with stir bars) placed on a stir plate at a slow pace. Cultures are stable and active for a week at least (stored at room temp or in the fridge) but will take considerably longer to start growing on the day you subculture (~3 hours rather than 1).</font><br> | ||
=====Prepare turbidity standards===== | =====Prepare turbidity standards===== | ||
As the populations of bacteria increase, the culture media gets increasingly turbid. Using the [http:// | As the populations of bacteria increase, the culture media gets increasingly turbid. Using the [http://en.wikipedia.org/wiki/McFarland_standards McFarland Turbidity Scale], it is possible to estimate the changes in turbidity. The results will not be as precise as what you would measure with a spectrophotometer, but the changes over time will be detected and the results can be graphed. | ||
[[Image:McFarland_table.PNG|center]]<br> | [[Image:McFarland_table.PNG|center]]<br> | ||
[[Image:Note mini.png]]''<font color = red> TEACHERS: ''these standards can be prepared well in advance of lab and are useful if you are running the protocols without access to a spectrophotometer.</font color> | [[Image:Note mini.png]]''<font color = red> TEACHERS: ''these standards can be prepared well in advance of lab and are useful if you are running the protocols without access to a spectrophotometer.</font color> | ||
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[[Image:Note mini.png]]''<font color = red> TEACHERS: ''If the entire growth curve (i.e. days 3, 4 and 5) is to be done in one class, you may have to start the early time points in advance. If you are dividing the growth curve into several short lab periods, be sure to store the cells in the fridge (~4°) until the next session. </font><br> | [[Image:Note mini.png]]''<font color = red> TEACHERS: ''If the entire growth curve (i.e. days 3, 4 and 5) is to be done in one class, you may have to start the early time points in advance. If you are dividing the growth curve into several short lab periods, be sure to store the cells in the fridge (~4°) until the next session. </font><br> | ||
=====Procedure, if no spectrophotometer is available===== | =====Procedure, if no spectrophotometer is available===== | ||
The turbidity of the bacterial populations can be estimated using the [http:// | The turbidity of the bacterial populations can be estimated using the [http://en.wikipedia.org/wiki/McFarland_standards McFarland Turbidity Scale]. This method uses suspensions of a 1% BaCl<sub>2</sub> in 1% H<sub>2</sub>SO<sub>4</sub> that are visually similar to suspensions of various populations of ''E. coli.''<br>[[Image:Turbidity_photo.jpg|thumb|center|400px| Turbidity comparisons for some bacterial cultures (left) and McFarland standards (right)]]<br style="clear:both" /> | ||
1. Following your teacher's instructions, obtain small clear test tubes containing the turbidity standards. The tubes should contain enough standard in each to fill the tube to a height of about 1 inch (2.5 cm) from the bottom. Make sure each tube is properly labeled with its turbidity standard number. If you are filling the tubes from stock bottles of the standards, use small tubes and place enough standard in each to fill the tube to a height of about 1 inch (2.5 cm) from the bottom.<br> | 1. Following your teacher's instructions, obtain small clear test tubes containing the turbidity standards. The tubes should contain enough standard in each to fill the tube to a height of about 1 inch (2.5 cm) from the bottom. Make sure each tube is properly labeled with its turbidity standard number. If you are filling the tubes from stock bottles of the standards, use small tubes and place enough standard in each to fill the tube to a height of about 1 inch (2.5 cm) from the bottom.<br> | ||
[[Image:Note mini.png]]''<font color = red> TEACHERS: ''The size of the tubes and the volume of sample and standard used is flexible. The important things are that the volume can obscure the thick black lines and that the samples and standards are prepared in the same fashion, as shown in the photo. </font color><br> | [[Image:Note mini.png]]''<font color = red> TEACHERS: ''The size of the tubes and the volume of sample and standard used is flexible. The important things are that the volume can obscure the thick black lines and that the samples and standards are prepared in the same fashion, as shown in the photo. </font color><br> | ||
