Early diagenesis and trophic role of extracellular DNA in different benthic ecosystems

Corinaldesi, Cinzia, Antonio DellÂ’Anno, Roberto Danovaro

Limnol. Oceanogr., 52(4), 2007, 1710-1717PurchaseEarly diagenesis and trophic role of extracellular DNA in different benthic ecosystems | DOI: 10.4319/lo.2007.52.4.1710

ABSTRACT: To provide new insights into the early diagenesis of extracellular deoxyribonucleic acid (DNA) and its relevance in trophodynamic processes, we collected sediment samples from a variety of coastal and deep-sea sites. Turnover times of extracellular DNA were approximately threefold shorter in coastal benthic systems than in deep-sea sediments (0.35 yr and 1.2 yr, respectively). This was due to the higher concentrations of bioavailable extracellular DNA in deep-sea over coastal sediments (19.8 ± 0.6 and 9.8 ± 2.6 mg DNA g-1, respectively), since deoxyribonuclease (DNase) activities did not show significant differences between sampling sites (135.8 ± 72.7 and 62.8 ± 19.0 ng DNA g-1 d-1, in coastal and deep-sea sediments, respectively). The coastal benthic systems were characterized by DNase activities per prokaryotic cell significantly lower than those of their deep-sea counterparts (0.12 ± 0.05 and 0.27 ± 0.06 fg DNA degraded cell-1 d-1, respectively), although carbon production per cell was not significantly different (6.9 ± 4.4 and 2.6 ± 0.9 fg C cell-1 d-1, respectively). These results suggest that DNase activity per cell may be more dependent on the amount of bioavailable substrate rather than on prokaryotic metabolism. Extracellular DNA may supply 20% and 47% of the daily prokaryote anabolic requirements for organic phosphorous in both coastal and deep-sea sediments, respectively. Overall, our data suggest that bioavailable extracellular DNA might represent an important nutrient source for benthic heterotrophic metabolism and open new perspectives for a better understanding of the factors that influence the functioning of benthic systems.

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