Indole-3-carboxaldehyde (3-Formylindole), a banlangen extract, is the product of the oxidative degradation of indole-3-acetic acid (IAA) by crude enzyme preparations from etiolated pea seedlings. It is identified as an active principle component in Marinomonas sp., and it efficiently inhibits biofilm formation by Vibrio cholerae O1 (VCO1) without selection pressure.