Indole-3-acetic acid is a monocarboxylic acid that is acetic acid in which one of the methyl hydrogens has been replaced by a 1H-indol-3-yl group. It has a role as an auxin, a plant hormone, a mouse metabolite, a plant metabolite and a human metabolite. It is a member of indole-3-acetic acids and a monocarboxylic acid. It is a conjugate acid of an indole-3-acetate. Indole-3-acetic acid , a well-known phytohormone, can also be a signaling molecule in bacteria and therefore can have a direct effect on bacterial physiology.