I have been interested in the Origin of Life since I was a high school student. To make my dream being a researcher of Origin of Life real, I have studied with many persons. The Society for the Study of the Origin and Evolution of Life Japan helped me realize my dreams. Many researchers who have been studied the Origin of Life may be on each path to each discipline, which their advisers had showed them, or they want to construct themselves. The researchers of this society must be able to become the helpers or the facilitators for the students and the researchers who want to study the Origin of Life, because the society is originally constructed with multidisciplinary, interdisciplinary, and transdisciplinary elements. With a thankful heart, I would like to celebrate the semicentennial Journal “Viva Origino” and the Society for the Study of the Origin and Evolution of Life Japan.
In my college age, I read the Japanese translation of “The Origin of Life” written by Oparin, though understood a little. During graduate school and postdoctoral position in Japan and USA, I started the research experience in the field of photosynthesis. After returning back to Japan, I started the research career in Tokyo Institute of Technology, where I started the research on the structure of genomic DNA of archaebacteria. We analyzed the characteristics of the last universal common ancestor, which we named Commonote commonote, and found that the species was hyper-thermophilic, based on the experimental results obtained by reproducing an enzyme possessed by C. commonote, in Tokyo University of Pharmacy and Life Sciences. Then, we started the research on microbiota in deep see hydrothermal system as well as high atmosphere. Later, we started the space experiment Tanpopo on the International Space Station. The research field is now called Astrobiology.
There are ample of research results related to the RNA-origin of life. The ribonucleotides were produced nonbiologically in aqueous media by a reaction process with drying steps. The ribonucleotides were polymerized without biological catalyst. RNA-replicating ribozyme with the length of 200 nucleotides capable of replicating 200-nucleotide-long template has been reported. The process from the protocell containing self-replicating ribozyme surrounded by lipid membrane to the last universal common ancestor Commonote commonote is proposed.
We evaluated biological activities in terrestrial extreme environment samples from Antarctica soils and submarine hydrothermal systems by measuring phosphatase activities. The soil of Site 8 (near a penguin rookery) showed almost the same level of phosphatase activities as usual surface soil sampled in Yokohama National University (YNU ) campus, while the soil of the other stations showed much less activities. Massive sulfide chimneys of submarine hydrothermal vents in South Mariana Backarc also showed phosphatase activities: The exterior part of the chimnies showed higher than the interior part, suggesting the prokarotic habitat and cell density. Alkaline phosphatase (ALP) in the extracts from the soil of Antarctica Site 8 and chimney samples was characterized by the laboratory-based enzymatic assessments. Among these profiles, firstly, the Antarctica ALP showed the maximal at 37℃, the chimney ALP showed the maximal at 90℃, while ALP from the YNU soil showed the maximal at 60℃. Secondly, the gel filtration chromatography showed that the ALP activity in both Antarctica and chimney samples was found mainly in the fraction whose molecular weights were around 100000 Dalton. The ALP activity was diminished with EDTA and was recovered with addition of zinc ion. The present results showed that zinc-containing metalloenzymes are present in the Antarctica soils and the chimneys in the hydrothermal system, and that phosphatases are useful bio-signatures for extant life in extreme environments. Phosphatase activity could be used for life detection in extraterrestrial environments, as well as for evaluation of biochemical function of prebiotic samples.