{"created":"2023-07-25T08:13:59.827305+00:00","id":14919,"links":{},"metadata":{"_buckets":{"deposit":"8d1ff983-365d-4836-b8e4-ca442a8d2bdb"},"_deposit":{"created_by":29,"id":"14919","owners":[29],"pid":{"revision_id":0,"type":"depid","value":"14919"},"status":"published"},"_oai":{"id":"oai:ir.kagoshima-u.ac.jp:00014919","sets":["70:72"]},"author_link":["134525"],"item_5_date_6":{"attribute_name":"作成日","attribute_value_mlt":[{"subitem_date_issued_datetime":"2019-09-11","subitem_date_issued_type":"Collected"}]},"item_5_date_granted_54":{"attribute_name":"学位授与年月日 ","attribute_value_mlt":[{"subitem_dategranted":"2019-09-20"}]},"item_5_degree_grantor_53":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_language":"ja","subitem_degreegrantor_name":"鹿児島大学"}],"subitem_degreegrantor_identifier":[{"subitem_degreegrantor_identifier_name":"17701","subitem_degreegrantor_identifier_scheme":"kakenhi"}]}]},"item_5_degree_name_42":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士(農学)","subitem_degreename_language":"ja"},{"subitem_degreename":"Doctor of Philosophy","subitem_degreename_language":"en"}]},"item_5_description_17":{"attribute_name":"ファイル（説明）","attribute_value_mlt":[{"subitem_description":"博士論文全文, 博士論文要旨(日本語), 博士論文要旨(English), 最終試験結果の要旨, 論文審査の要旨","subitem_description_language":"ja","subitem_description_type":"Other"}]},"item_5_description_4":{"attribute_name":"要約(Abstract)","attribute_value_mlt":[{"subitem_description":"本研究では，水耕栽培作物体内部への大腸菌の侵入条件，特に侵入に必要な最低菌密度（閾値）に及ぼす原生動物や常在細菌の菌密度や作物種について検討し，最終的には閾値を解明するために様々な実験を行った．\n1. 各種葉菜類を栽培中の水耕液に堆肥由来の非病原性大腸菌を接種し，植物体内部へと大腸菌が侵入するかどうか試験した．レタス，ホウレンソウ，およびコマツナでは大腸菌が植物体内部へと侵入したのに対し，コネギでは侵入しなかった．その際の大腸菌密度は，試験期間後に大幅 に減少しており，大腸菌の侵入が観察されなかったコネギにおいても同様であった．このため，侵入の閾値を正確に求めることはできなかった．\n水耕液に接種した大腸菌が急激に減少する原因を解明するため，希釈平板法および µC-FISH 法を用いて大腸菌密度を測定した．接種直後の大腸菌密度は， 3.3 × 10 7～1.1 × 10 8 であったが， 7日後には大幅に（4～7桁）減少し，希釈平板法と µC-FISH 法での菌密度にほとんど差はなかった．このことから，水耕液に接種した大腸菌が急激に減少する原因は viable but non culturable (VNC）化したためではないことが判明した．同時に，栽培後の水耕液を顕微鏡観察したところ原生動物が多数確認された．レタスへの大腸菌侵入試験では，大腸菌接種 5～7日後に原生動物数が増加していた．\n2. 水耕液に接種した大腸菌の減少の原因を解明するために， 0.2 µm または 1.0 µm のフィルターを用いて水耕液をろ過し，そのろ液に大腸菌を接種した．その結果，未ろ過の水耕液では大腸菌が大幅に減少したのに対し，ろ過した水耕液では大腸菌が全く減少しなかった．さらに，蛍光標識した大腸菌菌体（FLB）を水耕 液に添加し 30分間インキュベートしたところ，原生動物体内に FLB が多数取り込まれていることを確認した．以上のことから，水耕液に接種された大腸菌を原生動物が捕食していることが示唆された．さらに，細菌と原生動物のバイオボリュームを測定し，原生動物のバイオボリュームの増加量と大腸菌のバイオボリュームの減少量に矛盾がないことを確かめた．\n3. 原生動物が，水耕液に接種した大腸菌減少の主要因であることを解明したことから，水耕栽培作物への大腸菌侵入閾値の正確な解明のためには，原生動物の捕食作用を抑制する必要があることが明らかとなった．そこで，抗原生動物薬（メトロニダゾールおよびピランテルパモ酸塩）を用いて，原生動物を抑制することを試みた．高濃度のメトロニダゾール（500～1,000 mg/L）により原生動物の運動性が抑えられたが，水耕液に同濃度を添加したところ原生動物の捕食を抑制することには至らなかった．一方，ピランテルパモ酸塩はDMSOに溶解させる必要があるため，原生動物に有効な濃度を水耕液に添加すると，DMSOの影響からレタスに生育障害が出ることが判明した．そこで両薬剤の混合使用により原生動物を抑制することを試みたが，抑制できなかった．これらのことから，抗原生動物薬による水耕液中の原生動物を抑制することは適切でないことが判明した．液中の原生動物を抑制することは適切でないことが判明した．\n4. 水耕液中の大腸菌密度を維持するために，定期的に大腸菌を水耕液に接種することを試みた．その結果，水耕液中の大腸菌密度を5日間ほぼ維持することに成功し，原生動物存在下におけるレタスへの侵入閾値を解明することができた．すなわち，大腸菌密度が2 × 10 4 CFU/mLから1 × 10 5 CFU/mLの範囲で5日間維持されることである．\n以上のように，水耕液の衛生管理において，原生動物と細菌の相互作用は非常に重要なものであることを明らかにした．しかし今日まで，水耕液中の原生液中の原生動物に着目した研究はなく，本研究の成果は，今後の水耕栽培作物の衛生管理の進展に大きく寄与できると期待される．","subitem_description_language":"ja","subitem_description_type":"Other"},{"subitem_description":"To clarify the threshold cell density for the internalization of Escherichia coli into hydroponic vegetables, E. coli isolated from cow dung was inoculated into hydroponic medium and determined the dynamics of E. coli and protozoa were investigated.\n1. To investigate the internalization of E. coli into hydroponic leafy vegetables, E. coli was inoculated into hydroponic medium during cultivation. E. coli was revealed to internalize into lettuce, spinach, and Komatsuna plants, while not into small green onion plant. The cell density of E. coli was decreased markedly during cultivation in all plants. To clarify the cause of a quick decrease in the E. coli population, the cell density of E. coli was determined by using plate counting with coliform agar (CA) and the µC-FISH method. The cell density of E. coli decreased markedly by as much as 4 to 8 orders of magnitude during 7-day cultivation. Notably, very little difference was observed between counts by the plate method vs. the µC-FISH method. These results suggest that the decrease in the E. coli population was not due to a physiological change into the viable but non culturable (VNC) state but true death. Many protozoa were observed under a light microscope in hydroponic medium during plant cultivation.\n2. To clarify the cause of the decrease in the E. coli population inoculated into hydroponic medium, E. coli was inoculated into intact, 0.2 µm-filtrated or 1.0 µm-filtrated hydroponic medium after plant cultivation. As a result, E. coli decreased markedly in the intact hydroponic medium, but totally not in the filtrated hydroponic medium. Furthermore, fluorescently labeled bacteria (FLB) were prepared from E. coli culture and added into hydroponic medium. FLB was observed to be ingested quickly by protozoa (mostly ciliates and flagellates). These findings suggest that protozoa feed on E. coli inoculated in hydroponic medium. In addition, analysis of the bio-volumes of bacteria and protozoa observed to be showed that the increment of protozoan bio-volume and the decrement of E. coli bio-volume were in accordance with a prey-predator relationship.\n3. To elucidate the threshold cell density of E. coli for the internalization into hydroponic vegetables, antiprotozoal agents were investigated to inhibit protozoan predation. Metronidazole and pyrantel pamoate were selected and used. Protozoan motility was suppressed markedly at 500 to 1,000 mg/L of metronidazole, but no suppression of protozoan predation was observed in the hydroponic medium. Pyrantel pamoate was relatively water-insoluble and thus dissolved in DMSO, which was added into hydroponic medium at an effective concentration for protozoa. However, it was found that lettuce plants died due to the toxicity of DMSO. Therefore, attempts were made to inhibit protozoan predation by using a mixture of the two kinds of drugs, however, the mixture was not effective to inhibit protozoan activity.\n4. To compensate the the loss of cell density caused by predation by protozoa so as to maintain cell density of E. coli in hydroponic medium, E. coli suspension was added periodically into hydroponic medium. As a result, cell density of E. coli almost unchanged during 5-day incubation in hydroponic medium, resulting in elucidation of the threshold cell density for internalization into lettuce plant with the presence of protozoa, that is, E. coli population at a range of 2 × 10 4 CFU/mL to 1 × 10 5 CFU/mL maintained for 5 days.\nThese results suggest the importance in the interaction between bacteria and protozoa in hydroponic medium. To date, however, there has been no research focusing on protozoan behavior in the hydroponic environments except this study. The results of this study are considered to contribute greatly to progress in the hygiene management of hydroponic vegetable production in the near future.","subitem_description_language":"en","subitem_description_type":"Other"}]},"item_5_dissertation_number_55":{"attribute_name":"学位授与番号","attribute_value_mlt":[{"subitem_dissertationnumber":"甲連研第945号"}]},"item_5_publisher_23":{"attribute_name":"公開者・出版者","attribute_value_mlt":[{"subitem_publisher":"鹿児島大学","subitem_publisher_language":"ja"},{"subitem_publisher":"Kagoshima University","subitem_publisher_language":"en"}]},"item_5_subject_15":{"attribute_name":"NDC","attribute_value_mlt":[{"subitem_subject":"610","subitem_subject_scheme":"NDC"}]},"item_5_text_44":{"attribute_name":"備考","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"【指導教員：染谷孝】"}]},"item_5_text_47":{"attribute_name":"date.appl","attribute_value_mlt":[{"subitem_text_value":"【学位申請日】2019-05-28 "}]},"item_5_version_type_14":{"attribute_name":"著者版フラグ","attribute_value_mlt":[{"subitem_version_resource":"http://purl.org/coar/version/c_970fb48d4fbd8a85","subitem_version_type":"VoR"}]},"item_access_right":{"attribute_name":"アクセス権","attribute_value_mlt":[{"subitem_access_right":"open access","subitem_access_right_uri":"http://purl.org/coar/access_right/c_abf2"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"佐藤, 聖","creatorNameLang":"ja"},{"creatorName":"サトウ, キヨシ","creatorNameLang":"ja-Kana"},{"creatorName":"Sato, Kiyoshi","creatorNameLang":"en"}],"nameIdentifiers":[{"nameIdentifier":"134525","nameIdentifierScheme":"WEKO"}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2019-11-29"}],"displaytype":"detail","filename":"Diss_佐藤_聖_RNK945_2019.pdf","filesize":[{"value":"4.7 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kB"}],"format":"application/pdf","mimetype":"application/pdf","url":{"label":"Comments_Sato_Kiyoshi_rnk_945_2019","objectType":"other","url":"https://ir.kagoshima-u.ac.jp/record/14919/files/Comments_Sato_Kiyoshi_rnk_945_2019.pdf"},"version_id":"470bc8cc-9de8-42d3-ae75-8b8c4e98e016"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"jpn"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"doctoral thesis","resourceuri":"http://purl.org/coar/resource_type/c_db06"}]},"item_title":"水耕栽培環境における大腸菌と原生動物の相互作用に関する研究","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"水耕栽培環境における大腸菌と原生動物の相互作用に関する研究","subitem_title_language":"ja"},{"subitem_title":"Studies on the interaction between bacteria and protozoa in the hydroponic environments","subitem_title_language":"en"},{"subitem_title":"スイコウ サイバイ カンキョウ ニオケル ダイチョウキン ト ゲンセイ ドウブツ ノ ソウゴ サヨウ ニ カンスル ケンキュウ","subitem_title_language":"ja-Kana"}]},"item_type_id":"5","owner":"29","path":["72"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2019-10-25"},"publish_date":"2019-10-25","publish_status":"0","recid":"14919","relation_version_is_last":true,"title":["水耕栽培環境における大腸菌と原生動物の相互作用に関する研究"],"weko_creator_id":"29","weko_shared_id":-1},"updated":"2024-12-04T02:54:40.250407+00:00"}