Lab notes from 10/14

Quorum Sensing

Vibrio Fischeri are gram negative
-at low population density they do not grow
-at high population density they express the luciferase gene
-Luciferase breaks down ATP to produce energy to make light

Dr. Robson inoculated test tubes of seawater agar with V. fischeri
-They were then incubated for 24 hours with lots of oxygen flow at 25 degrees C

We then had to observe to see if they did glow and then streaked the V. fischeri on MSA, EMB, and nutrient agar plates.

-Brice Buryanek

Quorum Sensing
+Dense popoulations of bacteria have different gene expression than individual bacteria
-gene expression : turning on/off particular genes in an organisms genome
+How can bacteria sense a high population density and chnge gene expression?
-Quorum sensing bacteria continuously secrete autoinducer (AI)
-AI for all gram negative bact. is a homoserine lactone (HSL)
-HSL= small molecule, cheap and easy to produce
-Quorum sensing bacteria also have AI receptor on surface of cells (always producing AI gene)
-When AI binds to its receptor
+this triggers a change in bact. gene exppression
-AI gene (always on and producing AI molecule)
-AI receptor (on cell surface)

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