Detection of protease activity using gelatin zymogram. A putative collagenase in Bacillus anthracis Ames was cloned in pMBP and expressed in BL21(DE3)pLysS. Expression (E) and solubility (S) of the putative collagenase (BA0555) were confirmed by His-vision staining on Nu-PAGE. The purified protein was run on Nu-PAGE gel and stained with Coomassie blue to confirm the purity (P). Gelatin zymogram was performed to examine protease activity using 2 ng of the purified putative collagenase (C). Purification background using E. coli supernatant (B) and 2.5 ng of trypsin (T) were used as a negative and a positive control, respectively.