Week Five – Laboratory Cleanliness
This week: more of the same. I passaged my cells to new flasks, mixed some buffer and milk solutions, and distributed 110 mL of 0.25% trypsin to new 15 mL tubes. (Trypsin is an enzyme used to dislodge adherent cells from flasks.) So, why would I bother to put the trypsin in separate containers, when all of it’s going to be used to passage cells anyway?
A really big concern in the laboratory is maintaining aseptic conditions. Apparently, every year during the period CAPMM gets new, high-school-aged summer interns through the Aspiring Scientists Summer Internship Program (ASSIP), all the cells get infected. All the contaminated cells have to be tossed out, and all the experiments have to be re-started. Because once bacteria, viruses, and fungi have infiltrated a cell culture, you can’t guarantee they’re not interfering with results, no matter how much antibiotic you add to the cell media.
Even more terrifying is that, while bacteria and fungi are pretty easy to see under a microscope, both viruses and mycoplasma (extremely tiny bacteria that lack a cell wall) can go undetected until they cause significant adverse effect to a culture (Thermo Fisher 17). Mycoplasma infections, particularly, can “persist in culture without causing cell death” (which is a big, easily detected indication that’s something’s wrong) (Thermo Fisher 17). The mycoplasma can alter the “behavior and metabolism” of your cells unpredictably, and make your results irreplicable (Thermo Fisher 17). Measures to detect viral and mycoplasma contamination, via, say, fluorescent staining and microbiological assays, are usually undertaken regularly (Thermo Fisher 17). Still, a contamination case can ruin weeks of work and necessitate tossing out thousands of dollars of valuable cell culture supplies.
By separating the trypsin into smaller tubes and minimizing the number of times a pipette is put into a trypsin container, we can thus lessen the chance bacteria or viruses contaminate the trypsin and interfere with our experiments. For the same reason, we work with cells in a biological safety cabinet (which emits a steady stream of air to prevent micro-organisms from getting inside), dump liquid cellular waste into diluted bleach, autoclave used equipment, and spray everything, including our gloved hands, with 70% ethanol. On the plus side, I like cleanliness, so I actually kind of enjoy waging biochemical warfare on all the microorganisms around me.
Cell Culture Basics Handbook. E-book, Thermo Fisher Scientific Inc, 2020.