X1: BioBrick J33201 (07.07.08) X2: pSB1A2+dxs clone (as M2; BBa_K118000) (07.07.08) X3: pSB1A2+appY (from Plate 21, streak 3) (18 July 2008) X4: pSB1A2+crtB (as M36; BBa_K118002) (25.07.08: A