Hello colleagues,
I'm still new to cell culturing so I'm really paranoid about contamination. I found these worm-like fibers in some of my cell culture flasks. I attach photos here.
The cells are 3T3 mouse embryonal fibroblasts growing in DMEM medium with FBS and pen-strep. The microscope objective used here was 5x. Photos were taken with a smartphone through the microscope eyepiece (we don't have a proper camera on this microscope).
I asked my colleagues about these fibers, and they say that most likely the fibers are from cotton plugs used in serological pipettes, so it's not an infection. But I still want a second opinion, because I don't see these things in all flasks. I can think of threads of dead cells, protein fibers from serum, fungi or even invertebrates, but I don't have enough experience to tell.
I wuoldn't worry to much. In case of fungi infection in a few days you would have the entire flasked filled with not single fiber structures but extended clumps of hyphae. It looks more cotton to me and I had something similar when I was culturing cells.
In principle if they are not growing over time, or increase in number I wouldn't worry or stop your experiment, on the contrary if you see an abnormal change in your media pH or you see and increasin number of detached dead cells then I would start to question if that batch of cells is usable or not.
Hope it helps,
Best of luck!
Are you certain the fibres are in your cultures, and not simply fibres on the microscope lens/eyepiece? Sounds silly but good to check! Otherwise it is likely cotton (sterile) as your colleagues have suggested. If the cells are contaminated you should see cloudy media from dettached cells, or a change in media colour.
Keep an eye on it but it should be okay!
looks like some kind of dirt or hair. You can pour media on to a plate without any cells and check in microscope immediately and leave it for few days in the incubator and check again. If there fungal infection you will find other bacterial infection you cannot see in normal micrscope they are 1000 times smaller than your cells. But this is definitely not fungal infection.
Thank you everybody, now I'm almost positive that my cells are OK.
More details for those who asked: these things are definitely not on the objective, they float on the surface of the medium where dead cells are, and they move when I move the flask. The medium is transparent and changes color as usual from purple-red to orange-red in a few days. I don't want to pour the medum because then I would have drops on the outside of the bottleneck and some bacteria may use these drops to get inside. But most flasks don't have these things, so they are not a part of the medium, but rather come from flasks or pipettes. If this is indeed cotton, I have to admit that in some pipettes cotton is more loose than in others.
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