Summary Zoospores of the oomycete Phytophthora parasitica establish microbial spheroid microcolonies and biofilms on the surface of wounded leaves of their host, Nicotiana tabacum . The formation of microcolonies involves the movement of some zoospores towards attractants from wound sites, followed by their irreversible adsorption and the formation of a cluster of cells. These cells drive the migration of a second wave of zoos...