Characterization of agarose as immobilization matrix model for a microbial biosensor

Development of fluorescent protein-based biosensing strains: A new tool for the detection of aromatic hydrocarbon pollutants in the environment

The major sources for release of hydrocarbons into the environment include the effluents generated from chemical processing industries and ports. The introduction of such hazardous compounds into natural water bodies creates considerable disturbances in aquatic life and causes a threat to humans. Thus, it is essential to detect and quantify pollutants at various stages of the wastewater generation and treatment before they reach natural aquatic environments and contaminate them. This study reports the development of "biosensing strains" by cloning hydrocarbon recognizing promoter-operator and a reporter gene in bacterial strains for sensing the presence of pollutants at their lowest possible concentration. So far, various biosensing strains have been constructed with a fused promoter-operator region of the hydrocarbon degrading operons, but most of them use luxAB as a reporter gene. A novel approach in the present study aimed at constructing strains harboring two different fluorescent protein (FP)-based reporter genes for the quantification of multiple pollutants at a time. Two vectors were designed with a fusion of tbuT-gfp and phnR-cfp for the quantification of mono- and poly-aromatic hydrocarbons, respectively. The designed vectors were transformed into E. coli DH5α, and these strains were designated as E. coli DH5α 2296-gfp (containing pPROBE-Tbut-RBS-gfp-npt) and E. coli DH5α 2301-cfp (containing pPROBE-phn-RBS-cfp-npt). Both the developed recombinant strains were capable of successfully detecting mono- and poly-aromatic hydrocarbons in the range of 1-100 μM. The sensing capacity of recombinant strains was successfully validated with actual wastewater samples against available physico-chemical analytical techniques. The development of such recombinant microbial strains indicates the future for online contaminant detection, treatment quality monitoring and protection of aquatic flora and fauna.

A multi-channel bioluminescent bacterial biosensor for the on-line detection of metals and toxicity. Part I: design and optimization of bioluminescent bacterial strains

This study describes the construction of inducible bioluminescent strains via genetic engineering along with their characterization and optimization in the detection of heavy metals. Firstly, a preliminary comparative study enabled us to select a suitable carbon substrate from pyruvate, glucose, citrate, diluted Luria-Bertani, and acetate. The latter carbon source provided the best induction ratios for comparison. Results showed that the three constructed inducible strains, Escherichia coli DH1 pBzntlux, pBarslux, and pBcoplux, were usable when conducting a bioassay after a 14-h overnight culture at 30 °C. Utilizing these sensors gave a range of 12 detected heavy metals including several cross-detections. Detection limits for each metal were often close to and sometimes lower than the European standards for water pollution. Finally, in order to maintain sensitive bacteria within the future biosensor-measuring cell, the agarose immobilization matrix was compared to polyvinyl alcohol (PVA). Agarose was selected because the detection limits of the bioluminescent strains were not affected, in contrast to PVA. Specific detection and cross-detection ranges determined in this study will form the basis of a multiple metals detection system by the new multi-channel Lumisens3 biosensor.

Monitoring of environmental pollutants by bioluminescent bacteria

This review deals with the applications of bioluminescent bacteria to the environmental analyses, published during the years 2000-2007. The ecotoxicological assessment, by bioassays, of the environmental risks and the luminescent approaches are reported. The review includes a brief introduction to the characteristics and applications of bioassays, a description of the characteristics and applications of natural bioluminescent bacteria (BLB), and a collection of the main applications to organic and inorganic pollutants. The light-emitting genetically modified bacteria applications, as well as the bioluminescent immobilized systems and biosensors are outlined. Considerations about commercially available BLB and BLB catalogues are also reported. Most of the environmental applications, here mentioned, of luminescent organisms are on wastewater, seawater, surface and ground water, tap water, soil and sediments, air. Comparison to other bioindicators and bioassay has been also made. Various tables have been inserted, to make easier to take a rapid glance at all possible references concerning the topic of specific interest.