日本産スギヒラタケの個体群の顕著な生長変異 Remarkable growth variation in a natural Japanese population of <i>Pleurocybella porrigens </i>

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Abstract

2004年に、木材腐朽性の担子菌スギヒラタケを摂食した人、とりわけ慢性腎臓病患者に深刻な急性脳症が大発生した。急性脳症を引き起こす要因の主体は依然未解明である。これは、同菌の生長が極度に遅いことに一部起因している。このため、様々な分野の研究の進展に資する同菌の栄養生長に適する培地の探索を試みた。日本各地の地理的に異なる地点のスギとアカマツの枯木から分離した同菌の15菌株をポテトデキストロース寒天培地(PDA)で培養したところ、生長速度のみならずコロニー形態にも著しい変異が存在することが明らかになった。生長の速い5菌株を選抜し、5種類の液体培地[ポテトデキストロース培地(PD培地)、麦芽エキス・酵母エキス培地(MY培地)、ジャガイモ抽出液・ニンジン抽出液培地(PC培地)、甘酒培地、太田氏培地]で20℃、暗黒下で8週間、静置培養したのち、各菌株の乾燥重を量った。同菌の乾燥生物量を指標とした生長は、PD培地で最大値が得られ、次いで太田氏培地、MY培地、甘酒培地、PC培地の順となった。同一培地での液体培養において、いずれの供試菌株ともに生物量に顕著な変異がみられ、栄養菌糸体には発育不全の分枝が高頻度に発生しており、栄養生長が極めて遅い一因となっていると推察される。これらの結果から、日本産のスギヒラタケの個体群には顕著な生長変異が存在することが判明した。以上から、今後、栄養生長能の高いスギヒラタケ菌株を選び、PD培地や太田氏培地を用いて培養実験を行なえば、同菌の菌体化学成分と急性脳症の発症との関係の解明に寄与すると期待される。

In 2004, an outbreak of serious acute encephalopathy exclusively occurred in patients with chronic kidney diseases after the intake of basidiomycetous wood rotting fungus Pleurocybella porrigens. The exact factors that induced encephalopathy by this mushroom remain unknown partly due to its extreme slow growth. We attempted to develop media suitable for vegetative growth of P. porrigens for application in various fields. Fifteen isolates of P. porrigens collected from rotting conifers, Cryptomeria japonica and Pinus densiflora, in different geographical areas in Japan were cultivated on potato dextrose agar (PDA) medium; large variation in growth rate and colony features was observed among these isolates. The five isolates with the best growth rates were then cultured in five kinds of liquid media, potato dextrose (PD) medium, malt extract・yeast extract (MY) medium, potato extract・carrot extract (PC) medium, Amazake medium, and Ohta's medium at 20℃ in the dark. Dry biomasses of the isolates cultured in the liquid media were determined after 8 weeks of static cultivation. Among the tested liquid media, PD medium was the most suitable for biomass growth, followed by Ohta's, MY, Amazake and PC media. The average biomass growth of the isolates cultured in the synthetic medium (Ohta's medium) was 20-92% of that in PD medium. Remarkably large biomass variation was also observed among the isolates cultured on each liquid medium. Mycelia of this mushroom had abortive lateral branching at high frequency which could be one reason why this mushroom grows very slowly. Moreover, the Japanese population of P. porrigens has large variation in vegetative growth. Taken together, elucidation of the possible association between its chemical constituents and the onset of encephalopathy may be possible by culturing isolates with high growth ability on PD medium as a natural medium and Ohta's medium as a synthetic medium.

Journal

  • Japanese Journal of Food Chemistry and Safety

    Japanese Journal of Food Chemistry and Safety 18(1), 18-24, 2011

    Japanese Society of Food Chemistry

References:  11

Codes

  • NII Article ID (NAID)
    110008661323
  • NII NACSIS-CAT ID (NCID)
    AA11666400
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    1341-2094
  • NDL Article ID
    11145359
  • NDL Source Classification
    ZP34(科学技術--食品工学・工業)
  • NDL Call No.
    Z17-B99
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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