Recently, I make a test to growth B. subtillis on tryptic soy agar (TSA) by 2 ways.
1st: I spreading on TSA and incubate.
2nd: after spreading on TSA, I pour another layer TSA and incubate.
After incubate, the colony on 1st plate grow separate, but on 2nd plate, they spreading over whole plate.
I think it because their motility, but not sure about that.
Somebody know why?
P/s: I incubated them in same condition and spread with same volume.
Bacillus colonies do diffuse through the medium but for it to spread through the entire plate usually does not happen.
1. Try a quadrant streak with a loop of small diameter.
2. Add some amount of agar-agar separately to the medium.
Dear Khanh,
Bacillus subtilis cells are motile and to obtain individualized colonies the surface of the medium should be free of moist because it can let bacteria swarm over the plate.
The plates may be placed in a dryer for about 10min at 60 °C to evaporate the excess of moist. The dryer must be clean (to avoid contamination) and you can place the open plate with the agar side upside-down, supported over the edge of the top of the plate.
Best regards
Isabel
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