title: Effect of electrokinetic transport on the vulnerability of PAH-degrading bacteria in a model aquifer.
abstract: There has been increasing interest in employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics, to overcome the low bioavailability of hydrophobic organic contaminants (HOC) by homogenizing sorption-retarded HOC and immobilised microorganisms. Present electro-remediation approaches mainly aim at macroscale pollutant extraction and tend to neglect possible impacts of direct current (DC) on the physiology of microorganisms. The effect of weak electric fields (X = 1 V cm(-1)) on the fitness of electrokinetically dispersed fluorene-degrading Sphingomonas sp. LB126 in bench-scale model aquifers was investigated by flow cytometry using propidium iodide (PI) as an indicator that distinguishes between PI-permeable (cells with porous membranes, i.e. dead or vulnerable) and PI-impermeable bacteria. After 15.5 h of DC treatment 56% of all cells recovered were dispersed at the centimetre scale relative to 29% in the absence of DC. There was no overall negative effect of the 15.5-h DC treatment on cell vulnerability, as 7.0% of the DC-treated bacteria exhibited PI-staining compared to 6.5% of the control population. Minor differences were observed in the subpopulation that had been mobilised by electroosmosis with an approximately twofold increase in the percentage of PI-stained cells relative to the control. Enhanced PI staining did not correlate with reduced culturability of the cells on rich-medium agar plates. Relative to the control, DC-treated cells mobilised by electroosmosis were threefold more culturable, confirming earlier data that that PI-cell membrane permeability does not always indicate reduced viability of oligotrophic environmental bacteria. Our findings suggest that electrokinetics is a valuable mechanism to transport viable and culturable polycyclic aromatic hydrocarbon (PAH)-degrading bacteria in soil or sediments.
authors.affiliation: Department of Environmental Microbiology, UFZ Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Susann
authors.initials: S
authors.lastname: Müller
authors.forename: Hauke
authors.initials: H
authors.lastname: Harms
authors.forename: Lukas Y
authors.initials: LY
authors.lastname: Wick
mesh_terms: D001673:Biodegradation, Environmental; D015169:Colony Count, Microbial; D004560:Electricity; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism; D020578:Sphingomonas / Q000302:isolation & purification / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism; D014881:Water Supply
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical