What exactly is sugar water?
Well, it is exactly what it sounds like: sugar dissolved in water. Given the need for accuracy, the process of making sugar water in the lab is more difficult than simply going into your kitchen and grabbing sugar out of your cabinet but only slightly.
Sugar is actually a general term of a chemical that tastes sweet. Many similar molecules fall into the category. For example, the type of sugar used in cooking is sucrose. However, I tend to work with galactose and glucose.
Why? My bacteria like to eat those types.
I study adaptation.
Given that adaptive processes occur over very long time scales, creative solutions are needed to study adaptation.
There are essentially two options: 1) examine and compare organisms today to speculate how things happened or 2) use good microbial models to study adaptation over a manageable time scale.
Bacteria are an ideal for studying evolution because they live at a much faster rate than humans. In a single day, some bacteria I use in the lab will undergo roughly ten generations. Do you know what your great (x7) grandparents looked like? Probably not.
A simple start on a complex journey.
The natural world is complex. Similar to the field of unculturables, there is a lot to learn about what aspects of an environment bacteria utilize. Given this complexity, simple models are preferable, at least initially.
This is exactly why I use sugar water on a routine basis. It acts as the environment or selective pressure pushing my bacteria to adapt and change. If we can understand adaptation in this context, we might be able to say something about adaptation in general.
In fact, one experimental evolution experiment with E. coli adapting to sugar water has been on-going for 25 years or >58,000 generations and continues to teach us a lot. Check out this great infographic celebrating the anniversary of this great experiment!