Cell Culture

I have a love-hate relationship with cell culture. I love it because it is easy and you can get a lot of data from one cell culture experiment if you plan correctly. I hate it because it reminds me of my time working on a dairy farm when I was in college. You can never take time off when you have cells growing in the incubator. They require constant attention in order for them to grow properly. One of the unique things about cultured cells is that most of them will stop growing once they are in contact with other cells. The ones that aren't contact inhibited are cancer cells. Anyway, I am going to be doing a FACS (fluorescence activated cell sorting) experiment using a cell line called HEK 293. It is a kidney cell line that grows well and is generally easy to care for. Unfortunately, when I went to prepare my experiment today, every well of my 6-well plate was contaminated with mold. It was fine yesterday. The only thing I did was to take out one plate of the three to look at the cells under the microscope to make sure they were growing. They were and were doing so nicely. They were about 60-70% confluent which would mean that they would be ready for viral infection today or tomorrow. Now they are all in the biohazard trash.

I am not sure what the problem is, however, I am leaning toward that 6-well plates rather than the growth media or any of the things I am doing. My reasoning is this: the cells were growing fine with no contamination issues in other growth vessels and the media shows no signs of being contaminated. I generally make enough media for the week and store it in the incubator so that any contamination will be obvious as bacteria, yeast, and mold will grow like mad in the media. Most people make up their culture media in large batches and store it in the fridge, warming it up before each use. That makes it impossible to tell if there are any contamination issues in the media (the most common source) until you have already put the media on the cells. Another reason is that I had this same problem the last time I used this batch of 6 well plates but decided that the source of contamination was elsewhere.

I am going to start another batch of 293 cells growing today and when they get ready to split, I will put half of them in a 6 well plate that I have UV irradiated (killing anything with DNA) and the other half in a non-irradiated plate. Let's hope this little experiment solves my problem. I can't keep wasting time and resources with something as silly as contaminated 293 cells.