The technique utilizes the uidA gene of Escherichia coli, which codes for the enzyme, β-glucuronidase; this enzyme, when incubated with specific colorless or non-fluorescent substrates, can convert them into stable colored or fluorescent products.
ðə tɛknˈiːk jˈuːɾɪlˌaɪzᵻz ðə jˈuːɪd ɐ dʒˈiːn ʌv ˌɛʃɚɹˈɪkiə kˈoʊli, wˌɪtʃ kˈoʊdz fɚðɪ ˈɛnzaɪm, bˈeɪɾəɡlˈuːkjʊɹɹˌɑːnɪdˌeɪs; ðɪs ˈɛnzaɪm, wˌɛn ˈɪŋkjuːbˌeɪɾᵻd wɪð spəsˈɪfɪk kˈʌlɚləs ɔːɹ nˈɑːnflʊɹɹˈɛsənt sˈʌbstɹeɪts, kæn kənvˈɜːt ðˌɛm ˌɪntʊ stˈeɪbəl kˈʌlɚd ɔːɹ flʊɹɹˈɛsənt pɹˈɑːdʌkts.