Xavier Lab

Program for Computational Biology | Memorial Sloan-Kettering Cancer Center

Easy recipe for swarming plates

I prepare a bunch of 250 mL botles with 100 mL of agar at 1.25% that I sterilize, let solidify and keep for stock.
Then everytime I need to make swarming plates I melt the agar in the microwave and add the folowing ingredients:

Then I pour exactly 20 mL of medium per petri dish. It should be enough for 12 plates. I let cool down for 30 min and then flip upside down. Then I let cool down for 15 h (overnight).

Inoculate the swarming plate: Take an overnight culture of Pseudomonas aeruginosa grown in LB medium. Wash twice by spinning down the cells and resuspending in 1X PBS. Use a P10 pipette to spot 2 uL of the culture at the center of the swarming plate. You should let the 2 uL drop hang from the pipette tip and gently touch the agar surface. After inoculation let the droplet dry by leaving the plate open in you bench until the water is absorbed by the agar. Close the plate and incubate at 37 C for 24 h. The plate should be upside down in the incubator.

Text Box:  The protocol is quite robust but you need to take care with the following:

If you have suggestions let me know.

Joao

 

This recipe was used in:

Xavier JB, Kim W, Foster KR (2011) A molecular mechanism that stabilizes cooperative secretions in Pseudomonas aeruginosa. Mol Microbiol. 79(1):166-79. [pdf]

The following paper discribes a similar recipe and gives more tips for reproducible swarming

Tremblay J, Déziel E (2011) Improving the reproducibility of Pseudomonas aeruginosa swarming motility assays. Journal of Basic Microbiology 48(6):509–515. [pdf]