The genetic code is highly conserved. However, some bacteria-infecting viruses called phages have redefined the code, possibly to fine-tune the timing of lifestyle transitions.
The many genes of an organism are all not equally important. Which are crucial and how do they differ between bacteria?
A,T,C,G is our universal genetic alphabet, from viruses to human beings. But some viruses like to stand out from all of us and use another letter: Z.