Research Highlights: Microbes with high metabolic activity found in deep, hot subseafloor environment


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Microbes with high metabolic activity found in deep, hot subseafloor environment

  • About 25 percent of the world’s seabed sediment can be found at a depth where temperature is more than 80 °C.
  • Scientists previously proposed that 80 °C is the thermal barrier for life in the strata below the Earth’s surface.
  • Researchers discovered a population of methanogenic and sulfate-reducing organisms in deep buried marine sediment.
  • Methanogenic organisms produce methane as a metabolic byproduct in low oxygen conditions.[1]
  • Sulfate-reducing organisms can perform anaerobic respiration by using sulfate as terminal electron acceptor and reducing it to hydrogen sulfide.[2]
  • The IODP (International Ocean Discovery Program) Expedition 370 drilled and collected sediment cores in the Nankai Trough subduction zone just south of Japan.
  • The Nankai Trough subduction zone can reach temperatures of about 120 °C.
  • Subduction zone is the place where two plates of the Earth come together, one is found over the other.[3]
  • Researchers utilized a considerable suite of radiotracer experiments.
  • Radiotracers is a compound that contains a radioactive element and can be used to study the mechanism of chemical reactions.[4]
  • The small microbes discovered from the Nankai Trough subduction zone survived with high potential cell-specific rates of energy metabolism, similar to the rates in active surface microbes and laboratory cultures.
  • Researchers initially expected that the metabolic rates in the deep subseafloor will be extremely low.
  • The cells appear to expend almost all of their energy to repair damages from the high temperature.
  • At the same time, the cells are forced to balance between supporting themselves at a minimum level near the thermal barrier for life and a rich source of substrates and energy from the reactions of the sedimentary organic matter caused by the high temperature environment.

Sources:

Beulig, F., Schubert, F., Adhikari, R.R. et al. Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphere. Nat Commun 13, 312 (2022). https://doi.org/10.1038/s41467-021-27802-7

[1] https://en.wikipedia.org/wiki/Methanogen

[2] https://en.wikipedia.org/wiki/Sulfate-reducing_microorganism

[3] https://earthquake.usgs.gov/learn/glossary/?term=subduction%20zone

[4] https://www.iaea.org/topics/radiotracers


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Deep Sea Scientific Research in 2020

  • Aspergillus flavus is saprophytic soil fungus that infects crops. It also produces carcinogenic compound called aflatoxin. One study isolated A. flavus from deep-sea sediments of the Central Indian Basin. When the deep-sea fungal isolate was grown on defatted groundnut oil meal, it produces alkaline protease.
  • Researchers have determined the information on the sources and transformation of mercury in deep oceans. Mercury in marine food webs at about 500 meters, which human activity mostly occur, is transported to deep-sea trenches in decaying flesh of dead animals. The mercury is then incorporated into the deep-sea food webs.
  • A new Gram-positive, motile, aerobic, non-spore-forming and slender rod-shaped actinobacterium was isolated from deep sea water of the Indian Ocean. Phylogenetic analysis indicated that strain was grouped into a separated branch with Chryseoglobus frigidaquae. The strain contains genes involved in the biosynthesis of alkylresorcinol, ansamycin, and carotenoids. It was classified as a novel species of the genus Chryseoglobus. The proposed name is Chryseoglobus indicus sp. nov.
  • A whale-fall occurs when the carcass of a whale has fallen onto the ocean floor at a depth greater than 1,000 meters. These carcasses can create complex ecosystems that supply nourishment to deep-sea organisms. Researchers investigated the sediments from whale-fall ecosystems to reveal fungal communities in these unique marine environments. Composition at the phylum level among the samples was assigned to Ascomycota (46%), Basidiomycota (7%), unidentified fungi (21%), non-fungi (10%), and sequences with no affiliation to any organisms in the public database (No-match) (16%). Some of these unidentified fungi are allied to early diverging fungi and they were more abundant in the sediments not directly in contact with whalebone.
  • The deep sea represents the largest and the most unexplored biome on the planet. Researchers conduct the first systematic characterization of deep-sea invertebrate communities of the Galapagos, and they collected 90 biological specimens that were preserved and sent to experts around the world for analysis. Of those, 30 taxa were determined to be unknown and new to science, including members of five new genera (2 sponges and 3 cnidarians). Researchers also analyzed image frame grabs from over 85 hours of remotely-operated vehicle footage to investigate patterns of species diversity and document the presence of a range of underwater communities between depths of 290 and 3,373 meters, including cold-water coral communities, extensive glass sponge and octocoral gardens, and soft-sediment faunal communities.

Keywords: deep-sea, marine research, new ocean discovery, abyss research

Sources:

Damare, S., Mishra, A., D’Souza-Ticlo-Diniz, D., Krishnaswamy, A., & Raghukumar, C. (2020). A deep-sea hydrogen peroxide-stable alkaline serine protease from Aspergillus flavus3 Biotech10(12), 528. https://doi.org/10.1007/s13205-020-02520-x

Blum, J. D., Drazen, J. C., Johnson, M. W., Popp, B. N., Motta, L. C., & Jamieson, A. J. (2020). Mercury isotopes identify near-surface marine mercury in deep-sea trench biota. Proceedings of the National Academy of Sciences of the United States of America117(47), 29292–29298. https://doi.org/10.1073/pnas.2012773117

Pei, S., Xie, F., Wang, W., Zhang, S., & Zhang, G. (2020). Chryseoglobus indicus sp. nov., isolated from deep sea water. International journal of systematic and evolutionary microbiology, 10.1099/ijsem.0.004564. Advance online publication. https://doi.org/10.1099/ijsem.0.004564

Smith, C.R., Glover, A.G., Treude, T., Higgs, N.D., & Amon, D.J. (2015). Whale-fall ecosystems: recent insights into ecology, paleoecology, and evolution. Annual review of marine science, 7, 571-96 .

Nagano, Y., Miura, T., Tsubouchi, T., Lima, A. O., Kawato, M., Fujiwara, Y., & Fujikura, K. (2020). Cryptic fungal diversity revealed in deep-sea sediments associated with whale-fall chemosynthetic ecosystems. Mycology11(3), 263–278. https://doi.org/10.1080/21501203.2020.1799879

Salinas-de-León, P., Martí-Puig, P., Buglass, S., Arnés-Urgellés, C., Rastoin-Laplane, E., Creemers, M., Cairns, S., Fisher, C., O’Hara, T., Ott, B., Raineault, N. A., Reiswig, H., Rouse, G., Rowley, S., Shank, T. M., Suarez, J., Watling, L., Wicksten, M. K., & Marsh, L. (2020). Characterization of deep-sea benthic invertebrate megafauna of the Galapagos Islands. Scientific reports10(1), 13894. https://doi.org/10.1038/s41598-020-70744-1

https://www.annualreviews.org/doi/abs/10.1146/annurev-phyto-072910-095221?journalCode=phyto