Requisite morphologic interaction for attachment between Ulva pertusa (Chlorophyta) and symbiotic bacteria

In order to understand the morphogenesis-inducing mechanism of Ulva pertusa by symbiotic bacteria, we observed the requisite conditions of bacteria fo r attachment to U. pertusa for algal morphogenesis. Non-morphogenesis-induc ing bacterial mutants derived by ultraviolet irradiation did not attach ont o the surface of this alga. Scanning electron microscopic observation durin g the process of morphogenesis in U. pertusa revealed a network-like struct ure formed on the algal surface within 1 week after application of bacteria . The bacteria attached onto the alga after 2 weeks of incubation. After th is attachment process the morphologic change was observed in U. pertusa.