Maybe some of you have seen this before and have an idea of what I'm talking about
: I am passaging BEAS-2Bs in 10%FBD+DMEM media in a T75 flask. On the day that the cells were split, they appeared contaminant free (no changes in media color, no tubidity). There are no bubbles present when the flask is placed in the incubator. The next day, there will be small bubbles that have formed on the bottom on the flask. These bubbles are adherent to the plastic; they do not move with the media and there are no cells growing where the bubble is. Under the microscope, the bubbles appear to contain other small droplets or round colonies (if it is actually a contaminant). Over the course of several days, the bubbles do not multiply, nor do they grow in size. The cells and media likewise seem unaffected by them. We have only started seeing these bubbles about a month ago. All of our equipment underwent regular autoclaving/cleaning last week and we have no current contamination issues other than these strange bubbles that don't behave like contaminants. Has anyone ever seen this before? Could it be a contaminant? Could it be that the flasks have some small defects in the tissue culture treatment they are supposed to have? Am I just paranoid?