title: Application of luminescent biosensors for monitoring the degradation and toxicity of BTEX compounds in soils.
abstract: OBJECTIVE
  To assess the changes in acute toxicity and biodegradation of benzene, toluene, ethylbenzene and xylene (collectively referred to as BTEX) compounds in soil over time and compare the performances of biological and chemical techniques.
  
  
  RESULTS
  Biological methods (lux-based bacterial biosensors, basal respiration and dehydrogenase activity) were related to changes in the concentration of the target compounds. There was an initial increase in toxicity determined by the constitutively expressed biosensor, followed by a continual reduction as degradation proceeded. The biosensor with the BTEX-specific promoter was most induced when BTEX concentrations were highest. The treatment with nutrient amendment had a significant increase in microbial activity, while the sterile control produced the lowest level of degradation.
  
  
  CONCLUSIONS
  Luminescent biosensors were able to monitor changes in contaminant toxicity and bioavailability in aqueous extracts from BTEX-impacted soils as degradation proceeded. The integration of biological tests with chemical analysis enables a fuller understanding of the biodegradation processes occurring at their relative rates.
  
  
  CONCLUSIONS
  The biological methods were successfully used in assessing the performance of different treatments for enhancing natural attenuation of BTEX from contaminated soils. While, chemical analysis showed biodegradation of parent BTEX compounds in biologically active soils, the biosensor assays reported on changes in bioavailability and potentially toxic intermediate fractions as they estimated the integrative effect of contaminants.
authors.affiliation: School of Biological Sciences, University of Aberdeen, Aberdeen, UK. j.j.dawson@abdn.ac.uk
authors.forename: J J C
authors.initials: JJ
authors.lastname: Dawson
authors.forename: C O
authors.initials: CO
authors.lastname: Iroegbu
authors.forename: H
authors.initials: H
authors.lastname: Maciel
authors.forename: G I
authors.initials: GI
authors.lastname: Paton
mesh_terms: D001419:Bacteria / Q000302:isolation & purification* / Q000378:metabolism; D001554:Benzene / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D001555:Benzene Derivatives / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D001673:Biodegradation, Environmental; D015374:Biosensing Techniques; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D049449:Luminescence; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D014050:Toluene / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D014992:Xylenes / Q000032:analysis / Q000737:chemistry / Q000633:toxicity
chemical_list: D001555:Benzene Derivatives; D012989:Soil Pollutants; D014992:Xylenes; D014050:Toluene; D001554:Benzene; C004912:ethylbenzene