Meeting Abstract
Larvae of many marine invertebrate species are powerless to swim against ocean currents; they spend hours to weeks suspended in the water column searching for a suitable habitat to complete juvenile development. Larvae are stimulated to metamorphose by a settlement cue – an environmental stimulus that signals the presence of mates, an appropriate food source, or an appropriate environment for juveniles. While the chemical settlement cues are unknown for the majority of species, many species have been found to metamorphose in response to microbial biofilms. Here, we investigated whether the polychaete Capitella teleta would metamorphose in response to biofilms made by bacteria isolated from their native salt marsh sediment, which is also their food source. A single anaerobic bacterial colony was found that stimulated larvae of C. teleta to metamorphose in less than 30 minutes. We determined that the inductive bacterium is Desulfovibio oceani. To determine the inductive chemical produced by D. oceani, we separated extracts of the salt marsh sediment and D. oceani biofilm by TLC. We found one dark purple spot present with the same retention factor for both the salt marsh sediment and D. oceani biofilm. The chemicals in this spot stimulated larvae of C. teleta to metamorphose in under 30 minutes. It was found that the sediment purple spot contained menaquinones 6, 7, 8, 9, and 10, while the spot isolated from D. oceani contained only menaquinone-6. After testing a number of menaquinones, only menaquinone-6 successfully induced metamorphosis. These results suggest that larvae of C. teleta are using menaquinone-6 produced by D. oceani as a settlement cue indicating the salt marsh sediments they inhabit.
