chapter 10.2 case study, chemotaxis towards autoinducer 2 mediates autoaggregation in escherichia coli

aim:

explore whether chemotaxis and quorum sensing are involved in regulating autoaggregetation in E. coli

hypothesis

E. coli responds to AI2 (QS) by moving (chemotaxis), which promotes aggregation

background

Autoaggregation: occurs when bacterial cells at high density cluster together in a medium and then adhere to a surface

• Precede biofilm formation

• Bacteria that are deficient in autoaggregation are unable to form large biofilms

step 1: delete genes involved with swimming and chemotaxis

• Swimming genes: fliC, motA

Chemotaxis genes: cheY, tar, tsr

Why delete the genes?

• Swimming is controlled by chemotaxis

• Part of the hypothesis is that chemotaxis is involved in autoaggregation, need to test it

Which genes appear to be important in regulating autoaggregation? Select all that apply

step 2:

At which phase of growth is quorum sensing activated?

B. 

What is being measured here?

• % area of autoaggregation

• Can see diff phases of growth

What does an increasing OD mean?

• High od, high area, high rate

What conclusion can you draw from the graph?

• Higher OD causes faster aggregation formation

C. 

Which ghene(s) is/ are involved in regulating autoaggregation overall? Select all that apply

Which gene is the most important in regulating autoaggregation?

step 2:

Does the data match with what you would expect considering what all the other panels are showing?

step 3:

What is the Δflu strain used as?

• Has the biggest difference and is a -ve control

Other than flu, which gene is shown to be the most important for regulating biofilm formation?

• cheY and IsrB have no statistical diff but qualitatively isrB has a smaller area….

Based on the images, how does knocking out each gene affect the biofilm?

conclusions

• Autoaggregation occurs when there is higher cell density which is also when QS activates

• QS seems important in mediating autoaggregation

• Chemotaxis also plays a role in regulating autoaggregation

• Both chemotaxis and QS appear to be important for biofilm formation contributing to different characteristics of a good biofilm