In order to visualize if a bacteria grown on a starch agar plate is positive for amylase, ( must be added to the surface of the agar. if the bacteria is indeed positive for this enzyme, one would observe (2) around the bacterial growth.
(1) crystal violet / (2) an area of blue-purple staining
(1) gram iodine / (2) an area of blue- purple staining
(1) gram iodine / (2) an area of clearing or a non-stained halo
(1) methylene blue / (2) an area of clearing or a non-stained hal