Possible influence of bacterial quorum sensing on the hydrolysis of sinking particulate organic carbon in marine environments

A central component of the ocean's biological carbon pump is the export of sinking, photosynthetically derived, particulate organic carbon (POC). Bacteria colonize these particles and produce enzymes that hydrolyse sinking POC thereby acting as one of the major controls on the biological pump. Here we provide evidence that a bacterial cell-cell communication mechanism, quorum sensing (QS), may influence the activity of hydrolytic enzymes on sinking particles. We collected sinking POC from a site off Vancouver Island, Canada and found that it contained acylated homoserine lactones (AHLs), a suite of well-known bacterial communication molecules. Furthermore, we observed that the addition of exogenous AHLs to incubations containing sinking POC affected the activity of key hydrolytic enzymes involved in POC degradation in some cases. Our results suggest that AHL-based QS could play an important role in regulating the degradation of sinking POC and that variability in AHL-triggered POC hydrolysis is a heretofore unrecognized process that impacts the marine biological carbon pump.