Provided herein are microorganisms that include one or more heterologous nucleic acid selected from the group of a sequence encoding a 7-methylxanthosine synthase, a sequence encoding a theobromine synthase; and a sequence encoding a caffeine synthase, where the microorganism is capable of producing one or more purine alkaloid in a culture medium, when the microorganism is cultured under conditions sufficient to produce the one or more purine alkaloid. Also provided compositions and kits that include at least one of these microorganisms, and methods of producing one or more purine alkaloid that include culturing one of these microorganisms under conditions sufficient to produce the one or more purine alkaloid.