Whole-cell-based biosensors for environmental biomonitoring and application.
ABSTRACT A variety of whole-cell-based biosensors has been developed using numerous native and recombinant biosensing cells. The use of reporter genes, for example bacterial luciferase and gfp, to monitor gene expression is discussed in terms of each reporters' benefits and disadvantages, including their possible use on-line, their sensitivity, the need for extra substrate, etc. All biosensing cells in use can be classified into two groups in terms of their biosensing mechanisms--constitutive expression and stress- or chemical-specific inducible expression. In this review several examples of each are presented and discussed. The use of recombinant whole-cell biosensors in the field requires three components--biosensing cells, a measurement device, and a signal-transducing apparatus, the last two depending on the first and the final applications of the system. The use of different immobilization techniques in several studies to maintain the cells and their viability is also discussed, in particular their use in the development of both high-throughput and chip-based biosensing systems. Finally the application of whole-cell-based biosensors to different environmental media, such as water, soil, and atmospheric monitoring is discussed; particular attention is given to their use for detection of various stressors, including dioxins, endocrine-disrupting chemicals, and ionizing radiation.
Article: Pseudomonas fluorescens HK44: lessons learned from a model whole-cell bioreporter with a broad application history.[show abstract] [hide abstract]
ABSTRACT: Initially described in 1990, Pseudomonas fluorescens HK44 served as the first whole-cell bioreporter genetically endowed with a bioluminescent (luxCDABE) phenotype directly linked to a catabolic (naphthalene degradative) pathway. HK44 was the first genetically engineered microorganism to be released in the field to monitor bioremediation potential. Subsequent to that release, strain HK44 had been introduced into other solids (soils, sands), liquid (water, wastewater), and volatile environments. In these matrices, it has functioned as one of the best characterized chemically-responsive environmental bioreporters and as a model organism for understanding bacterial colonization and transport, cell immobilization strategies, and the kinetics of cellular bioluminescent emission. This review summarizes the characteristics of P. fluorescens HK44 and the extensive range of its applications with special focus on the monitoring of bioremediation processes and biosensing of environmental pollution.Sensors 01/2012; 12(2):1544-71. · 1.74 Impact Factor
Article: Toxicant identification by a luminescent bacterial bioreporter panel: application of pattern classification algorithms.[show abstract] [hide abstract]
ABSTRACT: Genetically engineered microorganisms, tailored to respond by a dose-dependent signal to the presence of toxic chemicals, are a potentially useful tool for environmental monitoring. One manifestation of this approach is based on a panel of luminescent bacterial bioreporters, harboring fusions of the luxCDABE operon to various stress-responsive gene promoters. Such sensors can report by a dose-dependent luminescent signal on the stress sensed by the cells and thus on the presence of toxic compound(s), but they lack the ability to identify the chemicals involved. Here, we demonstrate how the use of a panel of such sensors might offer a solution to this drawback. Five selected Escherichia coli reporter strains harboring fusions of selected gene promoters (grpE, nhoA, oraA, lacZ, and mipA) to luxCDABE were exposed to five model toxicants and to a toxicant-free control in a 40-repetition format. Each of the six treatments activated different promoters to different extents, producing its own unique fingerprint. Two machine learning schemes were challenged with the obtained data set: Bayesian decision theory and the nonparametric nearest-neighbor technique. The Bayesian classifiers performed better and were able to identify the sample's contents within 30 min with an error rate estimate that did not exceed 3% at a 95% confidence level and with zero false negatives. Performance in tap water and wastewater samples was similar. Given the coming of age of whole-cell sensing devices, pattern classification algorithms such as the ones described here offer a step toward the incorporation of reporter cells into future biosensor formats, including whole-cell arrays.Environmental Science and Technology 12/2008; 42(22):8486-91. · 5.23 Impact Factor
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ABSTRACT: Most environmental protection issues concern the often chronic exposure of large populations to low doses of chemical toxins and ionizing radiation. However, measuring the effects of low doses on populations exposed over long time periods is highly problematic. Politically driven opinions often tend to take the place of science. Part of the problem is that epidemiology is a weak tool when the level of exposure is low. High background levels of exposure, genetic diversity, and exposure uncertainties all contribute to “noise” and make dose-response relationships difficult to define. Uncertainty feeds anxiety, leading to polarized politics. This review looks at the promise of molecular technologies for identifying the effects of low doses of radiation and identifies some of the issues involved in defining risk after low-dose exposures. While the main pollutant discussed in this article is ionizing radiation, the analysis could apply equally well to other toxic exposures or to combined radiation and chemical pollutants.BioScience 09/2009; · 4.62 Impact Factor