So as an energy source. Now what this gene also does is we can actually use that protein produced by this gene, we can react it with a special type of analog molecule and that will give us the color blue. So it will cause the solution to turn blue and that can be used as a very good visual marker to basically differentiate between those plasmids that did take up, those cells that did take up the plasma, those cells that did not. So we see that the plasma also contains an origin of replication, as shown, as well as an antibiotic resistant gene that can be used as a marker in the way that we discussed earlier. But in addition to this, it also contains the beta galactose today's gene. This gene codes for an enzyme that breaks down sugars and can be used to give a distinct blue color when that enzyme reacts with a special analog molecule, as we'll discuss in a future lecture.