Ken Takai, Ph.D.
Program Director, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Dr. Takai received a Ph.D. in fisheries science from Kyoto University in 1997. He worked as a research fellow at the Japan Society for the Promotion of Science and the Japan Science and Technology Agency, and in 2009 became the program director of the Extremobiosphere Research Program at the Institute of Biogeosciences, and the unit leader of the Precambrian Ecosystem Laboratory at JAMSTEC. Since September 2012, he has also served as a visiting professor at JAXA’s Institute of Space and Astronautical Science. He specializes in the physiology and ecology of microorganisms and organisms that live in extreme conditions on Earth, such as the deep sea or the crust interior, as well as explaining the formation and structure of their ecosystems. He is an astrobiologist and geobiologist.
--- Please tell us about your organization, the Japan Agency for Marine-Earth Science and Technology.
JAMSTEC headquarters in Yokosuka, Kanagawa prefecture (courtesy: JAMSTEC)
Hyperthermophiles – microorganisms living near hydrothermal vents in the deep sea: (A) Thermococcus (B) Thermosulfidibacter takaii (C) Methanopyrus kandleri (courtesy: Ken Takai/JAMSTEC)
JAMSTEC is an advanced research institution that studies the Earth and its oceans. Working on the principle of understanding the Earth by studying the oceans, we conduct comprehensive research on the oceans, as well as the atmosphere, the oceanic crust and mantle, and marine life and its phenomena. We also have a motto: “Pure, Bright, Joyful.” As long as our research is funded by the nation, it seems natural for us to think about what we can do for the people and society. However, we think it is also important to conduct research that satisfies our own interests and curiosity, and which is fun for everyone involved.
--- What are you working on now?
My current research is on extremophiles – life forms that live in extreme conditions, such as very high temperatures and pressure. More precisely, I am studying life forms, particularly microorganisms, that live in totally dark environments, without any sunlight, in the deep sea and its subfloor. I think that by studying the ecosystem in this dark world we will be able to understand how life was born on Earth, and how the first life forms spread all over the planet. The goal of my research is to explain the origins of life.
--- Why are you looking for the origins of life not in space but in the deep sea?
It seems to me that the deep sea and space are the same in relation to life. Looking at deep-sea life forms, I often imagine similar life forms existing on other celestial bodies. I study deep-sea life forms because I believe that before we can explain the origin of life, we have to have an in-depth understanding of life on Earth. This is why I am investigating the boundaries of the biosphere. For instance, organisms living in the deep sea or in the oceanic crust are living on the very edge between places where life can and cannot exist. So, by studying these environments, it becomes possible to outline the zone in which life can be sustained. And if the same conditions are found on another planet, you have good reason to believe in the existence of life there. So I think that studying life forms in the dark world can also help us find extraterrestrial life.
--- What is the boundary of Earth’s biosphere like?
Methanogens can thrive in temperatures of up to 122°C (courtesy: Ken Takai/JAMSTEC)
JAMSTEC’s renowned manned research submersible SHINKAI 6500 (courtesy: JAMSTEC)
Vent chimney at the deep-sea floor of the South Pacific Ocean, along the Kermandec arc (courtesy: JAMSTEC)
My research has confirmed the existence of life in environments at temperatures as high as 122°C, and with a strong alkali of pH 12.4, respectively. This is the current world record. The organisms living in extremely high temperatures were found at the Kairei hydrothermal vent field in the Indian Ocean, and the ones living in the strongly alkaline environment were found in a sample collected from the sub-seafloor of the South Chamorro Seamount, one of the submarine volcanoes running from the Mariana Trench to the Mariana Islands.
QUELLE 2013, the round-the-world voyage by the manned research submersible SHINKAI 6500, took place this past summer, in June and July. On this voyage, we conducted a survey near the Cayman Islands, in the Caribbean Sea. This location has the deepest hydrothermal vent field in the sea, at a depth of over 5,000 meters, and water as hot as 400°C. In addition, the hot water there has the highest hydrogen concentration – more than 20 millimolars. If we can find a new life form there, it will further expand the boundaries of life on the Earth. On June 22, 2013, we webcast the submersible exploration survey by SHINKAI 6500 in the Caribbean. This summer’s research may yet produce a great discovery that will shock the world!
Related link: The round-the-world voyage QUELLE2013
--- That sounds very exciting. Is there anything living near the hot water?
The chimney-like structure that forms around a hot-water vent on the sea floor is called a deep-sea hydrothermal vent chimney. Regular hot springs reach temperatures of about 120°C, but at a depth of 2,500 meters, water spews out at about 350°C, as a result of fluid pressure. So any living organisms you find in these conditions are known as hyperthermophiles – that is, they like high temperatures. A single gram of matter from the chimney can contain 20,000 different kinds of microorganisms.
--- 20,000 kinds! How is it possible for them to thrive in such an extreme environment?
The hot water from a hydrothermal vent is spewing energy, and these living organisms live on it. The water conveys matter, which is the source of energy, and microorganisms turn it into organic compounds. Thanks to the microorganisms, there are a lot of nutrients there, and this allows many creatures to thrive, even in the deep sea, where sunlight cannot penetrate. The energy of the hot water is provided by the energy of the Earth’s interior. And hyperthermophiles are thought to be the oldest life forms on Earth. We think that life on Earth may have originated in deep-sea hot water.
The deep-sea world is absolutely dark. But with an infrared camera, you can see a bright spot where there’s a hot spring. This is because of the presence of a number of life forms. They look totally different from creatures on the surface. Looking at them, I cannot help feeling the depth and power of life. This is the very thing that we are trying to explain.
--- What are the necessary conditions that allow life to exist?
Scale worm that lives in the deep sea (courtesy: Yoshihiro Fujiwara/JAMSTEC)
The essential elements for the birth of life are, first, energy, and next, matter to form an organism. For instance, the main elements that make up a human body are carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus. Living organisms exhale matter and regenerate cells, so we need to ingest matter, not just energy. And food contains both. Namely, what is essential for life is a continuous supply of enough energy to live and of the elements that make up a living organism. To put it the other way round, as long as an environment can provide these conditions, life can exist. However, such an environment cannot support a large number of organisms for an extended period if it exists only momentarily, in just one area of a planet. Temporal and spatial elements are also key. What makes Earth special is the fact that such an environment has been sustained for as long as 4.6 billion years on a global scale. This is why there are so many living things on the planet.
--- So it takes multiple conditions for life to be able to exist. I have the impression that there is high potential for the existence of life where there is water.
Mars rover Curiosity (courtesy: NASA/JPL-Caltech/MSSS)
Although the presence of water is an important condition for the existence of life, it does not automatically promise the existence of life at all. NASA’s Mars rover Curiosity is now looking for organic compounds on Mars, but the existence of organic compounds does not guarantee the existence of life either. As I explained earlier, life cannot exist without energy and a supply of elements. Also, scientists are using telescopes to look for a “green planet,” which would suggest the presence of vegetation, or a planet that has water as well as oxygen. But I think that such planets are very rare, even among the ones that can sustain life. This means that many opportunities to find life in space are being overlooked. Of course, it would be amazing if you could score a goal on your first attempt – it would be like winning a lottery. But I think it’s important to have a deep understanding of the different aspects of the existence of life, and then work on the search for extraterrestrial life by gradually narrowing down the list of candidate planets that have the potential for life. I think that is a good approach to advancing the search for extraterrestrial life as a science.
