Viva Origino
Online ISSN : 1346-6933
Print ISSN : 0910-4003
Volume 35, Issue 3
Displaying 1-5 of 5 articles from this issue
  • Takeshi Saito
    2007 Volume 35 Issue 3 Pages 85-92
    Published: 2007
    Released on J-STAGE: January 18, 2022
    JOURNAL FREE ACCESS

      Some terrestrial microorganisms can survive in extremely severe environments, such as high temperature, high salt, strong acid and strong alkali condition. Elucidation of the adaptive mechanisms of these extremophiles against extreme environments will provide very meaningful information to consider the evolution and the diversity of organisms. Some bacteria show considerably high resistance to ionizing radiation. D37 of Escherichia coli is 40 Gy, while D37 of Deinococcus radiodurans which is representative radioresistant bacterium is 7 kGy. D37 is the dose required to leave 37% of the original population viable. It is thought that radioresistances of radioresistant bacteria depend on high DNA repair activities, high antioxidant activities, special cell structures and uncommon intracellular environments. Information of radioresistant mechanisms in these bacteria will be helpful for elucidation of protective mechanisms of organisms against the stresses to damage cellular constituents. This review deals with recent advances in the study of the radioresistant mechanisms in the radioresistant bacteria.

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  • Masaomi Hatakeyama
    2007 Volume 35 Issue 3 Pages 93-97
    Published: 2007
    Released on J-STAGE: January 18, 2022
    JOURNAL FREE ACCESS

      In this short review, studies concerning life systems are summarized from the viewpoint of emergent properties. In the systems science and philosophical areas, the word ‘emergence’ has generally been used for the appearances of new properties in a whole system, which possesses a hierarchical structure and involves many elements interacting with each other. Additionally, in the complex systems science the undecompositionality between the system and the parts are taken into account. From the standpoint of ‘emergence’ it is discussed what kind of properties are necessary for the life system, which can evolve, and some issues concerning evolution are discussed in the last chapter.

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  • [in Japanese]
    2007 Volume 35 Issue 3 Pages 98-100
    Published: 2007
    Released on J-STAGE: January 18, 2022
    JOURNAL FREE ACCESS

    Sources of prebiotic amino acids on the early Earth can be classified into those having extraterrestrial origin and those that have formed on Earth. The extraterrestrial origin via carbonaceous chondrites is widely accepted as a major source of prebiotic amino acids, because many of these carbonaceous chondrites actually contain amino acids. Besides this, formation of prebiotic amino acids on the early Earth can also be another possible source. Although the atmosphere of the early Earth was thought to be only slightly oxidative, wherein amino acids could hardly be synthesized, some recent experimental and theoretical studies have suggested the existence of locally and transitionally reducing atmospheres that are generated by the impact of ordinary chondrites onto the early oceans. Such a reducing environment has the possibility to generate prebiotic organic materials.

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  • Shohei Ohara
    2007 Volume 35 Issue 3 Pages 101-103
    Published: 2007
    Released on J-STAGE: January 18, 2022
    JOURNAL FREE ACCESS

      Peptide formation is an essential process in chemical evolution. It is still an open question as to what event in the early history of the Earth might have caused polymerization of the organic molecules. Several experiments which simulate oceanic environments (e.g. lagoon or hydrothermal vent) have been attempted. However, in principle, such environments are chemically and thermodynamically inadequate for the formation of peptides, i.e. the dehydration reaction.

      The grain-boundary spaces in deep sediments, during diagenesis in the early history of the Earth, have been recently proposed as a chemically and geologically viable place for prebiotic polymerization.

      Herein, I review previous studies concerning peptide formation and introduce a new hypothesis on the chemical evolution in the Earth’s crust.

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