Microbiology (hopefully) made accessible!

  A lot of tissue culture (“TC”) work in the lab involves growing “adherent cells” – basically you grow cells stuck to dishes or plates. The cells need plenty of space (but not too much – they need some friends!) and plenty of media (food). Since the cells will keep replicating, making more copies of themselves, they’ll quickly run out of both (generally every few days depending on how dense you plate them originally). So, before they do (typically when they’re at ~80% confluency (covering 80% of the surface of the dish)) you detach them from the dish, dilute them in fresh media, and plate them in a new dish.  We call this “passaging.” One of the ways we commonly detach cells is with a trypsin/EDTA solution. Trypsin is a serine protease, a pretty generic protein chewer.  But the basic thing you need to know for now is just that it chews proteins. And you know what’s causing the cells to stick to the (specially-treated) surface of the dish and to one another? Proteins!!! S...

  If you want cells to grow happily in a dish, you need to feed them the food that they wish! Mammalian cell culture media (the liquid food you feed them) can be complicated because different cells want different things (different growth factor & nutrient requirements, etc.) and they’re not used to growing in dishes! Media often consists of some sort of base media containing   salts ,   amino acids ,   pH   buffers, sugar, etc. And then you supplement that with things that 1) are specialized for that cell type or experiment and/or 2) are unstable so you have to add right before use. One thing you often have to add is some sort of serum (cell-less blood), typically Fetal Bovine Serum (FBS). This has the growth factors, trace minerals, and carrier proteins needed to help get things into cells, keep toxins out of cells, etc. Problem is that these sera can have batch-to-batch variability and also contain stuff that can interfere with downstream experiments (also...