Extracellular DNA Plays a Key Role in Deep-Sea Ecosystem Functioning

摘要

The regeneration of phosphates from the organic P pool is a key step in the regulation of P availability in the oceans (1). However, the reason why organic P is preferentially recycled in the deep ocean, where phosphates are not limiting, has yet to be clarified. This limits our understanding of the P cycle and ecosystem functioning on a global scale (2). DNA is a P-rich molecule (10% weight to weight), but the role of DNA in P cycling has largely been ignored to date, as it is typically viewed onlyas the genetic material associated with living biomass (3). Here we provide evidence that DNA concentrations in deep-sea sediments worldwide are extremely high (0.31 ± 0.18 g of DNA m~(-2) in the top centimeter) (4) and that more than 90% of the DNA inthese sediments is extracellular. We first estimated the extracellular DNA fraction by calculating the difference between total DNA and the DNA within living biomass, determined by synoptic determinations on virus, prokaryote, unicellular eu-karyote (protozoan), and small metazoan (meiofauna) abundances. Another approach, conducted with a nuclease-based procedure that degrades only the extracellular DNA, supports this finding, revealing that 60 ± 4% of the total DNA pool is enzymatically digestible (4).