TnphoA construct was derived from the transposon Tn5, which contained a kanamycin resistance gene flanked by two IS50 elements. This construct contains a version of the alkaline phosphatase gene with its signal sequence and promoter deleted, which will result in a blue colony phenotype on X-phos (5-bromo-4-chloro-3-indolyl phosphate toluidine salt) containing media when secreted into the peripl...