研究のタイプ: 医学/生物学の研究 (experimental study)

[実験モデル帯水層におけるPAH分解細菌の動電的分散に影響を与える要因] med./bio.

Factors influencing the electrokinetic dispersion of PAH-degrading bacteria in a laboratory model aquifer.

掲載誌: Appl Microbiol Biotechnol 2008; 80 (3): 507-515

この研究は、汚染土壌の電気的なバイオレメディエーション(微生物の働きによって汚染物質を分解し,環境の改善を図る技術)に関連し、弱い電界が地表面下の汚染物質分解微生物にどの程度の影響を与えるかを調べた。実験室において、直流(DC)電界(1 V / cm)を印加した帯水層モデル中のスフィンゴモナス属の一種LB126のフルオレン分解における動電輸送および沈着に影響を与える要因を評価した。15時間のDC処理後の浮遊細胞およびマトリックス結合細胞の空間分布に対する細胞サイズ、細胞膜の完全性、細胞染色体含有量(すべてフローサイトメトリーで評価)、細胞表面電荷および細胞疎水性の影響を評価した。 その結果、DC印加下では、細胞は主に電気浸透(液体と固体が接している所に電圧をかけた場合に液体が移動する現象)によって、見かけ上の速度0.6 cm/ hでカソードに移動し、細胞の僅かな分画のみが電気泳動によってアノードに移動した;対照的にDCが存在しない場合、注入ポイント周辺に細菌ガウス型分布が見られた;電界の存在下および不在下でガラスビーズ細胞とほぼ同じ分布を示したことから、DCは沈着効率に影響を与えなかった;細胞をヨウ化プロピジウム染色し、フローサイトメトリー分析したところ、動電的移動による細胞壁の完全性は、DCによる負の影響を受けないことが示され、細菌生理学的適応度 (生き延びるのに適した性質)は変わらないことが示された、と報告している。

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研究目的(著者による)

To evaluate the factors influencing the electrokinetic transport and deposition of fluorene-degrading bacteria (Sphingomonas spec.) in a laboratory model aquifer (packed with glass beads) exposed to a direct current electric field typically used in electro-bioremediation measures.

詳細情報

Electro-bioremediation is a hybrid technology of bioremediation and electrokinetics for the treatment of soil contaminated with hydrophobic organic compounds. Electrokinetics has the potential to enhance the contact probability of the bacteria and their hydrophobic organic compounds substrates by transporting bacteria to contaminant sources or vice versa.
Bacterial transport in porous media is the result of either electrophoretic movement of negatively charged bacteria to the anode and/or bacterial migration with the electro-osmotic water flow to the cathode.
Total numbers of adherent and suspended cells were quantified and analysed at distinct distances from the injection point (0 cm), and at 4.5, 9, and 15 cm towards both electrodes.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1:
  • DC/static
ばく露時間: continuous for 15 h

General information

More information on setup: Wick LY, Manic PA, Watliou P, Harms H (2004) Elctrokinetic transport of PAH-degrading bacteria in model aquifers and soil, Environ Sci Technol 38:4596-4602

ばく露1

主たる特性
周波数
  • DC/static
タイプ
  • electric current
ばく露時間 continuous for 15 h
ばく露装置
ばく露の発生源/構造
  • electrode
チャンバの詳細 two electrode chambers (2 x 7 x 3.5 cm) at the ends, a lid-covered model aquifer chamber (35.5 x 4 x 3.5 cm) in between and a bypass channel below the aquifer chamber having hydraulic contact with both electrode chambers to exclude advective hydraulic water flow through the aquifer chamber; chambers filled with buffer; aquifer chamber packed with glass beads
Sham exposure A sham exposure was conducted.
Additional information 1 ml of bacterial inoculum was slowly injected during 1 min at half of the bed depth at equal distance from the two electrodes in the centre of the aquifer chamber.
パラメータ
測定量 種別 Method Mass 備考
電界強度 1 V/cm - - - -
電流密度 1.8 mA/cm² - - - -

ばく露を受けた生物:

方法 影響評価項目/測定パラメータ/方法

研究対象とした生物試料:
調査の時期:
  • ばく露後

研究の主なアウトカム(著者による)

In presence of DC the cells were predominantly mobilised by electro-osmosis to the cathode with a velocity of 0.6 cm/h, whereas a minor fraction was mobilised to the anode by electrophoresis. Different electrokinetic behaviour of individual cells could be solely attributed to intra-population heterogeneity of the cell surface charge. In the absence of DC by contrast, a Gaussian-type distribution of bacteria around the point of injection was found.
DC had no influence on the deposition efficiency, as the glass beads in presence and absence of an electric field retained quasi-equal fractions of the cells. Propidium iodide staining and flow cytometry analysis indicated the absence of negative influences of DC on the cell wall integrity of electrokinetically mobilised cells and thus point at unchanged physiological fitness of electrokinetically mobilised bacteria.
Given the right conditions and organisms, electrokinetic dispersion could be used to distribute specialised bacteria in hotspots of contamination, e.g. in aquifer sediments.

研究の種別:

研究助成