Localization of kabiramides in the sponge Pachastrissa nux and sponge surface-attached bacteria

The sponge Pachastrissa nux has been reported to be a rich source of cytotoxic macrolides. In our previous study, we found that the P. nux sponge has the ability to develop the capitum part, a gorgonian-like structure that sprouts from the substratum-attached base, and accumulate the macrolides predominantly in the protruding capitum. Using kabiramides B, C, and G as markers, here we demonstrate the impact of kabiramides allocation on the sponge surface-attached bacteria. The population density of bacteria that attach to the surface of the capitum part and also on the appendage extending from the core base part was significantly less than that on the surface of the base itself. Selected bacteria were identified, but no unusual bacterial species that may be specific to the sponge were detected. Although too premature to conclude whether the sponge intentionally produces such toxic metabolites as chemical defense against the microbial foulers, or otherwise the settling microbes affect the chemical allocation, the correlation between the macrolide accumulation and the attachment of bacteria on the sponge's surface clearly shows how the sponge has adapted to fit in its specific environment and how it interacts with the microbial cohabitants.