Does bacteria transmitted from one flask to another through air circulation - (May/07/2008 )
If one culture flask that contain cells in the incubator is contaminated,will it contaminate other culture flasks in the same incubator? Because the air is circulating in the incubator and we used to loosen the cap of our flasks inside the incubator.
It is possible, but not very common. I would recommend using filter top flasks to eliminate this sort of problem.
Filter top flasks can prevent the bacteria contamination comes from other flasks? But is it possible that the bacteria can penetrate the filter membrane and contaminate the flask?
Contamination is unlikely unless the cells in one of the flasks fail to start growing. After a while a stray cell that has been caught into an aerosol particle might float into the (effectively) sterile flask, and start growing. In all of the other flasks (which did start growing an active culture), the competition for resources means the "flask invader" would be effectively competed out.
Cells in my flask are still growing although I can see some small dot-liked particles (bacteria-liked) moving slowly inside my flask (when I observed under highest magnification using inverted microscope). I'm not sure whether these small small particles are bacteria or not. They didn't turbid the medium and the medium looks clear. But I'm getting more debris inside my flasks. I change medium every 2-3 days. Can it be some kind of contamination?
They could be contaminated. Is the pH of the medium staying the same? Try taking a bit of your media and putting it in a flask/tube without cells, grow for a while - if you get the particles forming, them you have contamination.
The filters on the flasks have 0.2 micrometer pores - small enough to filter out most bacteria (but not mycoplasma), but definitely large enough for gas exchange.