Deep-sea ecosystems play a crucial role in global carbon cycles, and microbes there are the primary drivers of biogeochemical cycling. However, our understanding of microbial ecological roles in deep-sea ecosystems remains limited due to the challenges of collecting samples and performing experimental manipulations. In this study, we examined in-situ degradation of detrital diatom cells at 1,040 meters below sea level for 4 months in a submarine canyon, to investigate microbial responses to organic matter from (simulated) descending bloom detritus. Among the 107 high quality prokaryotic metagenomic assembled genomes (MAGs), 39 have higher abundances in terms of coverage at the latest time point. Four Alpha- and one Gamma-proteobacteria Five MAGs encoded hydrogen cyanide synthases, which generates the compound fatal for most of life. Yet, MAGs encoded capabilities for detoxifying this poison via the cyanide hydratase and a rhodanese are found. Rhodanese generates a less toxic metabolic product, thiocyanate, and we found MAGs that then degrade thiocyanate using cyanase and thiocyanate hydrolase. We also observed that genes encoding proteins responsible for arsenic- and mercuric-resistance were widespread across MAGs. MAGs that increased abundance with time contained more of the poisoning and detoxification genes above than those that had decreased abundances during organic matter degradation. Compared to deep-sea hydrothermal vents as research hotspots, much less attention was paid to pelagic deep-sea microbes, and our study revealed that microbes encode diverse metabolisms for managing environmental toxicity.

Primary Presenter: Yu-Chen Ling, Ocean EcoSystems Biology (lchacol@gmail.com)

Authors:

Yu-Chen Ling,   ()

Theo Krueger,   ()

Fabian Wittmers,   ()

Rachel Harbeitner,   ()

Sebastian Sudek,   ()

Alexandra Worden,   ()