生分解性プラスチックの分解速度はその構造とそれが置かれた微生物環境によって決まるが, 後者を制御することは微生物の多様性から困難であるとされている. しかしながら, プラスチックを含む有機廃棄物処理の観点から見ると使用後は速やかに分解する微生物環境を人為的に管理する必要性がある. そこで本研究では, 従来から有機農法において用いられている, 安定な循環サイクルを有する有用微生物 (EM) 群を生分解性プラスチック (L-ポリ乳酸) の置かれた有機廃棄物中に添加してその分解促進効果について調べた. その結果, 36℃でEM菌群をコンポスト中に添加した場合にL-ポリ乳酸の分解が約40%促進されることがわかった. また, コンポスト中での分解は非晶相から進行するが50℃でEM菌群を添加した場合には, 結晶相でも速やかな分解が起こることが明らかになった.

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Laboratory experiments were carried out on water quality purification with EcoBio-Block (EBB). EBB is a porous concrete block including Bacillus subtilis natto group. In this study, we examined experimentally denitrification effect of EBB by letting it live together with denitrification bacteria in soil. The time variations of TN, ON, DIN, NH₄-N, NO₂-N, and NO₃-N were obtained under the aerated condition by changing the weight ratio of EBB to water. On the basis of those data, the denitrification rate, the mineralization rate, and the decreasing rate of DIN were obtained. As a result, we confirmed that the processes of organic matter decomposition, nitrification, and denitification were performed effectively by the symbiosis of useful microbial group and denitrifying bacteria.

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Laboratory experiments were carried out on water quality purification of EBB (EcoBio-Block), which is a porous concrete block including Bacillus subtilis natto group. The abilities of EBB for the mineralization of organic matter and the nitrification of ammonium (NH₄-N) were tested and compared with those of common porous concrete blocks. The mineralization of organic matter was suppressed when the water temperature is low, and the generation of NH₄- N was kept low. Therefore, the nitrification by EBB was also suppressed. As the water temperature became high, the generation speed of dissolved inorganic nitrogen (DIN) by EBB increased outstandingly. The nitrification speed took the maximum value when the water temperature was 15°C. The experimental results revealed that EBB has the very high abilities for the mineralization of organic matter and the nitrification of NH₄-N though they depend strongly on the water temperature.

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植物共生科学は植物と共生微生物（群）の相互作用の解明を目的とする基礎科学であるが，当該分野の進歩は生命科学の幅広い諸分野に大きな影響を及ぼす．本稿では，植物共生の生態学的意義について解説した後，有用微生物の探索・選抜や機能解析，微生物ゲノム解析の進歩，植物における有用微生物制御系の発見，植物共生系の網羅的分析技術の開発，施肥条件や光環境を通した共生微生物制御，共生科学的視点からの「おいしさ」の科学的解明などの最近のトピックスと，関連する応用科学分野での今後の新たな研究展開の可能性について私見を紹介したい．

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In the regional development, a balance of development and preserving of natural resource should be considered. The precious natural environment has to be maintained. The Lake Ogawara in Aomori Prefecture is a brackish lake. The Takase river estuary is the tidal river, which connects the Pacific Ocean with the lake. The field observation of water quality was carried out for this lake in the period from August to December, 2002. These results indicate the seasonal changes of chlorophyll-a and turbidity.

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