Controlling Cellular Density

The characterization of KillerRed

To reach our goal of controlling cell density in a culture, we need to know how KillerRed affects our cells. This means characterizing its effects on the culture in several ways.

One of the first things we noticed is that LB medium is unsuitable for characterization of the protein. The main reason is that the composition of the culture medium isn't controlled, and that results can be inconsistent from one lot of LB medium to another. Another reason is that it is more difficult to modelize the effect of KillerRed on growth in rich medium like LB. First of all cells quickly reach stationary phase and the effects of KillerRed take a long time to show in certain situations. Second is that cell growth isn't quite logarithmic in LB, which can hide the effects of KillerRed. Since this data is particularly important for our model, we need a medium in which the cells have a fully logarithmic, reproducible and slow growth curve. M9 is such a minimal medium.

Upon inducing production of the protein with the PLac promoter, cell growth would be affected and slow down in LB medium. When we tried to switch to minimal M9 medium in order to get more reliable results