Sulfide indole motility (SIM) medium is used to detect sulfide reduction, indole production, and motility.  The left tube is H₂S negative and contains a nonmotile organism.  The right tube is H₂S positive, indicated by the black streak, and contains a motile organism based on the diffuse growth.  The indole test was not performed on these tubes. (Ken Van Horn, Focus Diagnostics, Inc., Cypress, CA)