 This concept has previously been explored as a means to circumvent the unwanted release of potentially pathogenic genetically modified bacteria.It was proposed that an auxotrophic strain of "Escherichia coli" (X1776) could be used for all genetic modification practices, as the strain is unable to survive without the supplementation of DAP, and thus, cannot live outside of a laboratory environment.Lysine has also been proposed to be involved in calcium intestinal absorption and renal retention, and thus, may play a role in calcium homeostasis.