The Mariana Trench Challenger Deep at 10897 m, the deepest point in the world’s ocean, is featured today around the world media. The reason: the successful descent, and return to the sea surface, of the vehicle Deepsea Challenger, designed and manned by Hollywood director and ocean explorer James Cameron. Cameron is the third human being to reach this depth, following the pioneer descent of Jacques Piccard and Don Walsh in the “Trieste” batiscaf in 1960. This is quite a remarkable feat, mostly because of the revolutionary design of the submersible Cameron built for this purpose, and one that reminds us that the challenges of the exploration of the ocean rival with those of space exploration. For a comparison, four times as many people as those that have descended to the Challenger Deep have walked on the moon and 500 times more people have climbed to the highest peak on earth, mount Everest.
But what may have Cameron seen? Most likely nothing remarkable, a deep, thick darkness, with - if lucky - scattered sparks of bioluminescence, likely triggered by the turbulence created by his vehicle and not much more. Certainly none of the beasts and monsters he imagined in his science fiction movie The Abyss (1989). Most likely a really boring descent, if no doubt full of adrenaline.
Because the ocean, particularly the deep ocean, is a microbial ecosystem. Indeed, the Challenger Deep has been sampled recurrently using unmanned autonomous vehicles notably the Japanese unmanned deep-sea submersible Kaiko (in Japanese, Ocean Trench). The samples collected by Kaiko have lead to discoveries of extreme bacteria. In a series of papers, the microbial flora of the sediments of the basin were reported (e.g. Takami et al. 1997). In 1998, Takai and coworkers reported two new bacteria species able, not surprisingly of growing at extreme pressures . A decade later, Takai and co-workers reported a new bacteria species, which they named Thermaerobacter marianensis, capable of growing very fast (90 min doubling time) at very high temperatures (optimum: 75 °C). Unfortunately, Kaiko was lost during a typhoon and has now been replaced by the Japanese vehicle ABISMO (Automatic Bottom Inspection and Sampling Mobile) able to descend 11,000 m into the ocean.
Granted, this is not as exciting as imaginary bioluminescence monsters, but likely of far greater consequences for science. Indeed, extreme bacteria, isolated from deep, warm ocean waters affected by volcanic activities have delivered a large number of genes and proteins of interest in industrial processes, from bioenergy to biotech, with a huge market value. Enzymes functional at high pressure and high temperature are likely to be able to catalyze processes at very high rates and yields (Arrieta et al. 2010).
Let’s welcome a long overdue new era in the exploration of the deep ocean! But expect discoveries to come from coccoid microorganisms, not large fluorescent monsters, which habitat is to be found in fantasy books.
Arrieta, J.M., S. Arnaud-Haond, and C.M. Duarte. 2010. What lies underneath: Conserving the oceans’’ genetic resources. Proceedings of the National Academy of Sciences 107; 18318-18324
Kato, C., L. Yi, Y. Nogi, Y. Nakamura, J. Tamaoka, and K. Horikoshi. 1988. Extremely Barophilic Bacteria Isolated from the Mariana Trench, Challenger Deep, at a Depth of 11,000 Meters. Applied and Environmental Microbiology 64: 1510-1513.
Takai, K., A. Inoue and K. Horikoshi. 1999. Thermaerobacter marianensis gen. nov., sp. nov., an aerobic extremely thermophilic marine bacterium from the 11000 m deep Mariana Trench. Int. J. Systematic and Evolutionary Microbiology 49: 619-628.
Takami, H., Inoue, A., Fuji, F. and Horikoshi, K. 1997. Microbial flora in the deepest sea mud of the Mariana Trench. FEMS Microbiology Letters, 152: 279–285