I was about to harvest my 2.5L cell cultures and noticed tiny spheres at the bottom of the 5L flask. They looked like tiny dots that were white. Under the microscope they didn't seem to be any fuzzy edges they were perfect spheres that were very durable (attempted to split on open with end of pipette tip and failed). They also didn't seem like they were interacting at all with the cells around them i.e. the cells were sticking to the orbs at all. These spheres were not floating but were only at the bottom of the culture. When we used the microscope to see them under green light it showed simply an absence of color. What could this contamination be?
Additional Information:
-Cell viability looked healthy, cell density was following appropriate trend. I didn't notice any orbs throughout the entire scale up process until I was ready to harvest at a cell density of 4e6 c/mL.
-I used fresh FreeStyle 293 media every time I scaled up
-Aseptic technique was used during cell culturing
-It appears that other cultures in the same incubator are free of contamination
Firstly, you should consult with your supervisor or professor since they are the resources for you to answer this type of question. Secondly, you may want to post a photo of the contamination so somebody may be able to tell what it is. I hope this helps.
According to your description, it feels like mycoplasma contamination. Otherwise can be protozoa contamination. They don't effect the cell growth as such.. but these are contamination and cells will not be healthy for long.
Mycoplasma contamination can come from less antibiotic content during media preperation.
And protozoa contamination comes due to sterilization issue. Try to sterilize all the container and co2 chamber properly. Wipe the desk with 70% alcohol all the time before use
I agree when it could be contamination from mycoplasma. It is the most common form of contamination. Maybe bacteria. I think bacteria could have this colour. I think the size does still match.I do not think virus could do.
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