BISC314:Lab4: Difference between revisions
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<center><font face="trebuchet ms" style="color:#FFFF00" size="5">'''BISC314: Environmental Microbiology'''</font><br> | |||
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[[BISC314:Lecture Syllabus | <font face="trebuchet ms" style="color:#FFFF00"> '''Lecture Syllabus''' </font>]] | |||
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'''LAB #4: Quorum sensing - chemical signaling within our community'''<br> | |||
Many bacteria are able to secrete signals into their environment that they can then utilize to determine their own density. Since bacteria are single-celled organisms, why do you think they would they be interested in knowing how many of them are near? A very well studied example of the quorum sensing system comes from ''Vibrio fisheri'', a bacterium that produces light only at high densities. If you think about it, the light produced by a single bacterium is unlikely to be seen by anyone so ''Vibrio'' wait until they have reached a "quorum" before turning on the metabolic pathway that creates light. In this way, a gene regulatory network is actually controlled by cell density. To hear more about it from another source, see this YouTube video of [http://www.youtube.com/watch?v=1NoxOs-hcRU Bonnie Bassler]. <br> | |||
Today we will be testing if any of your isolates are secreting Auto-Inducer (AI) into the surrounding media. Specifically, we will be using a strain of bacterium called ''Chromobacterium violaceum''. This organism is gram-negative and normally found in the soil. It produces a very strong purple pigment (hence the name) in response to levels of AI. We will also use a violacein-negative, mini-Tn5 mutant of ''C. violaceum'' (CV026) which can produce pigment in response to the AI from other bacteria but can no longer secrete its own AI - this will be our biosensor. <br> | |||
1. Label your agar plates. You will draw a line down the middle of the plate and write CV026 on one side and your isolate code on the other side. Also label a plate for our positive control, the parent strain to CV026: ''Chromobacterium violaceum ATCC 12472''. <br> | |||
2. Flame your loop. Use your loops to dip into an overnight culture of CV026. Streak 1/2 of an agar plate with this organism (the side with the CV026 label). <br> | |||
3. Flame your loop. Grab a relatively large amount of your isolates and streak them near to the CV026 streaks. Re-flame your loop. <br> | |||
4. Dip the loop into an overnight culture of ATCC 12472 and streak it near to the CV026 streak.<br> | |||
5. Place your plates upside down till next week. If your isolates are producing AI sensed by CV026, you will see a purple pigment.<br> | |||
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