The natural herbicide, cyanobacterin, specifically disrupts thylakoid membrane structure in Euglena gracilis strain Z

Cyanobacterin is a natural product produced by the cyanobacterium (blue‐green alga), Scytonema hofmanni. The compound has been chemically characterized and shown to inhibit electron transprot in photosystem II. Although the herbicide is lethal to photoautotrophs, photoheterotrophically‐grown organisms such as Euglena gracilis can survive and grown in saturating concentrations of cyanobacterin. Electron micrographs of treated E. gracilis cells show extensive damage to the thylakoid membranes of the chloroplasts, similar to the effects observed with 3‐(3, 4‐dichlorophenyl)‐1, 1‐dimethyl urea (DCMU). Unlike the synthetic herbicide, cyanobacterin specifically disrupts thylakoid membranes and does not affect other cellular membranes or heterotrophic growth.