理工学部 教員紹介

明石 基洋

アカシ モトヒロ  (Motohiro Akashi)

基本情報

所属
成蹊大学 理工学部 理工学科 助教
学位
博士(バイオサイエンス)(東京農業大学)

J-GLOBAL ID
201801016026744719
researchmap会員ID
B000341347

外部リンク

論文

 11
  • Motohiro Akashi, Masaharu Takemura, Seiichi Suzuki
    Frontiers in Microbiology 15 2024年5月2日  査読有り筆頭著者責任著者
    Giant viruses, categorized under Nucleocytoviricota, are believed to exist ubiquitously in natural environments. However, comprehensive reports on isolated giant viruses remain scarce, with limited information available on unrecoverable strains, viral proliferation sites, and natural hosts. Previously, the author highlighted Pandoravirus hades, Pandoravirus persephone, and Mimivirus sp. styx, isolated from brackish water soil, as potential hotspots for giant virus multiplication. This study presents findings from nearly a year of monthly sampling within the same brackish water region after isolating the three aforementioned strains. This report details the recurrent isolation of a wide range of giant viruses. Each month, four soil samples were randomly collected from an approximately 5 × 10 m plot, comprising three soil samples and one water sample containing sediment from the riverbed. Acanthamoeba castellanii was used as a host for virus isolation. These efforts consistently yielded at least one viral species per month, culminating in a total of 55 giant virus isolates. The most frequently isolated species was Mimiviridae (24 isolates), followed by Marseilleviridae (23 isolates), Pandoravirus (6 isolates), and singular isolates of Pithovirus and Cedratvirus. Notably, viruses were not consistently isolated from any of the four samples every month, with certain sites yielding no viruses. Cluster analysis based on isolate numbers revealed that soil samples from May and water and sediment samples from January produced the highest number of viral strains. These findings underscore brackish coastal soil as a significant site for isolating numerous giant viruses, highlighting the non-uniform distribution along coastlines.
  • Seiichi Suzuki, Hikaru Ugajin, Motohiro Akashi, Christine D.A.P. Wiyono, Motohiro Ohkura, Akihiro Arakawa, Shoichi Uchihara
    2023 15th Biomedical Engineering International Conference (BMEiCON) 2023年10月28日  査読有り
  • Motohiro Akashi, Ichiro Fujihara, Masaharu Takemura, Mitsuru Furusawa
    Journal of theoretical biology 538 111044-111044 2022年4月7日  査読有り
    Organisms consist of several genetic factors differing between species. However, the evolutionary effects of gene interactions on the evolutionary rate, adaptation, and divergence of organisms remain unknown. In a previous study, the 2-dimensional genetic algorithm (2DGA) program, including a gene interaction parameter, could simulate punctuated equilibrium under the disparity mode. Following this, we verified the effect of the number of gene interactions (gene cluster size) on evolution speed, adaptation, and divergence using the advanced 2DGA program. In this program, the population was replicated, mutated, and selected for 200,000 generations, and the fitness score, divergence, number of population, and genotype were output and plotted. The genotype data were used for evaluating the phylogenetic relations among the population. The gene cluster size 1) affected the disparity and parity mutagenesis modes differently, 2) determined the growth/exclusion rate and error threshold, and 3) accelerated or decelerated the population's speed of evolutionary advancement. In particular, when the gene cluster size expanded, the rate of increase in fitness scores decreased independently of the mutation rate and mode of mutation (disparity mode/parity mode). The mutation rate at the error threshold was also decreased by expanding the gene cluster size. Dendrograms traced the genotypes of the simulated population, indicating that the disparity mode caused the evolutionary process to enter 1) a stun mode, 2) an evolution mode, or 3) a divergence mode based on the mutation rate and gene cluster size, while the parity mode did not cause the population to enter a stun mode. Based on the above findings, we compared the predictions of the present study with evolution observed in the laboratory or the natural world and the processes of ongoing virus evolution, suggesting that our findings possibly explained the real evolution.
  • Akashi M, Takemura M
    Viruses 11(12) 2019年12月  査読有り
  • Akashi M, Takemura M
    Microbes and environments 2019年10月  査読有り

所属学協会

 3

共同研究・競争的資金等の研究課題

 2