Press Release
Unique ecology of a deep-sea amphipod from the world’s deepest ocean
area in the Marianas Trench and discovery of a novel cellulase
Dr. Hideki Kobayashi of Microbial Genome Research Group (Senior Research Associate) and his colleagues have been investigating the ecology of an amphipod (Hirondelleagigas) living in the Challenger Deep of the Marianas Trench (10,900 m depth). The amphipod Hirondelleagigas is an amazing creature living in the deepest part of the Mariana Trench. The H. gigas thrives at low temperatures, extreme pressures, and very nutrient-poor environments at the bottom of deepest sea. The existence of the deepest sea lives was known from 1960s, however,
their lifestyle as well as their foods was still unknown. What are they eating? We caught 185 amphipods using bait traps on the “ASHURA” (an 11,000-m class free-fall sediment sampler with a camera system), and analyzed the activities of digestive enzymes in H. gigas. As the result, we found that H. gigas survives, in part, by digesting plant materials that have sunk into the hadal sea. They accomplish this by producing enzymes of amylase, cellulase, mannanase, and xylanase (Fig. 1). The H. gigas contained much glucose, maltose, and cellobiose, which were products of their digestive enzymes in their body. We succeed in
purifying H. gigascellulase (HGcel) from 10 amphipods, and analyzed its enzymatic property. HGcel produced glucose and cellobiose from carboxymethyl cellulose at a molar ratio of 2:1 (Fig. 2). We found that HGcel can digest even sawdust, which is one of the possible substrates for bio-ethanol production. Furthermore, HGcel reacted on plain paper, and produced glucose at room temperature without water (Fig. 3). HGcel was a novel cellulase, and showed very different property from known cellulases of other organisms. This makes it an excellent candidate for industrial production of ethanol, an important biofuel.
The deepest sea was the extra high pressure, low temperature, and nutrient-poor environment, whose sediments contained organic carbon less than 6 ppm/g (dry-weight). H. gigas adapted to the deepest nutrient-poor environments by eating sunk plants. HGcel helps its getting nourishment by one-step production of glucose from cellulose. This work has been published on August 16, 2012 (PLoS ONE 7(8): e42727).
The content of this press release has been introduced in National Geographic and New Scientists.
Genomic Analysis of Deeply Branching Thermophile
Provides Clues to Early Life on Earth
Metagenomic analysis of the microbial community in the hot stream of a Japanese epithermal mine revealed that Candidatus ‘Acetothermus autotrophicum’ (Ca. ‘A. autotrophicum’), an uncultivated thermophilic bacterium, was keeping an ancient metabolic pathway for CO2 fixation and energy generation, known as acetyl-CoA pathway. The acetyl-CoA pathway is considered to have been inherited from the last universal common ancestor (LUCA), a cell from which all life has evolved. Bacteria and Archaea are believed to have evolved from LUCA.
Phylogenetic trees based on proteins conserved in bacteria and archaea showed that Ca. ‘A. autotrophicum’ is very near to their common ancestor. Ca. ‘A. autotrophicum’ also retains a thermostable bifunctional fructose 1,6-bisphosphate (FBP) aldolase/phosphatase, a gluconeogenic enzyme assumed to work effectively in the early Earth environments. This suggests that Ca. ‘A. Autotrophicum’ is the archaeorganism still retaining functional properties of early life on Earth.
These results will considered to become direct evidence showing the existence of the functional traits in the first free-living (autotrophic) bacterial and archaeal ancestors, and provide new insights into the dawn of life to the earliest phases of evolution from the genomic point of view.
The study has just been published on January 27, 2012 in the online journal of Public Library of Science ONE (PLoS ONE), vol. 7, e30559 by Takami et al.
Title: A deeply branching thermophilic bacterium with an ancient acetyl-CoA pathway dominates a subsurface ecosystem.
Authors: Hideto Takami1・, Hideki Noguchi2・, Yoshihiro Takaki1・, Ikuo Uchiyama3・, Atsushi Toyoda4・, Shinro Nishi1・, Gab-Joo Chee1・, Wataru Arai1・, Takuro Nunoura1・, Takehiko Itoh2・, Masahira Hattori5・, and Ken Takai1
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
- Department of Biological Sciences, Tokyo Institute of Technology
- Laboratory of Genome Informatics, National Institute for Basic Biology, National Institutes of Natural Sciences
- National Institute of Genetics
- The University of Tokyo
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