Abstract
The coelomic fluid of Glycera dibranchiata is bactericidal for the Gram-negative rod, Serratia marcescens. An active factor has been partially purified using gel chromatography and affinity chromatography on concanavalin A-Sepharose, and has been shown to be a glycoprotein with a molecular weight of 2.5-4.5 x 105 containing bound divalent cations and at least one disulfide bridge. The active molecule showed no biochemical similarities to other humoral bactericidal systems, either vertebrate or invertebrate, and would appear to define a new class of antibacterial molecules.