Main Technological Advancements in Bacterial Bioluminescent Biosensors Over the Last Two Decades.

Environmental quality assessment is an extensive field of research due to the permanent increase of the stringency imposed by the legislative framework. To complete the wide panel of measurement methods, essentially based on physicochemical tools, some scientists focused on the development of alternative biological methods such as those based on the use of bioluminescent bacteria biosensors. The first report dedicated to the development of such biosensors dates back to 1967 and describes an analytical system designed to address the problem of air toxicity assessment. Nevertheless the available technologies in the photosensitive sensors field were not mature enough and, as a result, limited biosensor development possibilities. For about 20 years, the wide democratisation of photosensors coupled with advances in the genetic engineering field have allowed the expansion of the scope of possibilities of bioluminescent bacterial biosensors, allowing a significant emergence of these biotechnologies. This chapter retraces the history of the main technological evolutions that bacterial bioluminescent biosensors have known over the last two decades. Graphical Abstract.

Detection of Metal and Organometallic Compounds with Bioluminescent Bacterial Bioassays.

Chemical detection of metal and organometallic compounds is very specific and sensitive, but these techniques are time consuming and expensive. Although these techniques provide information about the concentrations of compounds, they fail to inform us about the toxicity of a sample. Because the toxic effects of metals and organometallic compounds are influenced by a multitude of environmental factors, such as pH, the presence of chelating agents, speciation, and organic matter, bioassays have been developed for ecotoxicological studies. Among these bioassays, recombinant luminescent bacteria have been developed over the past 20 years, and many of them are specific for the detection of metals and metalloids. These bioassays are simple to use, are inexpensive, and provide information on the bioavailable fraction of metals and organometals. Thus, they are an essential complementary tool for providing information beyond chemical analysis. In this chapter, we propose to investigate the detection of metals and organometallic compounds with bioluminescent bacterial bioassays and the applications of these bioassays to environmental samples. Graphical Abstract.

Potential of Raman Spectroscopy To Monitor Arsenic Toxicity on Bacteria: Insights toward Multiparametric Bioassays.

In the field of toxicological bioassays, the latest progress in Raman spectroscopy opens new research perspectives on a fast method of observing metabolic responses against toxic agents. This technique offers a multiparametric approach, providing an overview of the physiological changes that are caused by pollutants. However, physiological spectral fingerprints require complex chemometric methods for proper analysis. In this study, particular attention has been given to the elaboration of an "aberrant spectra" detection strategy to highlight the effects of arsenic on the bacteria Escherichia coli. This strategy significantly improved spectra classification, consistent with a dose-response effect of the four tested concentrations of the metal. Indeed, the correct classification score of the spectra increased from 88 to more than 99%. The exposure time effect has also been investigated. The fine analysis of Raman spectroscopy fingerprints enabled the design of different "spectral signatures", highlighting early and late effects of arsenic on bacteria. The observed variations are in agreement with the expected toxicity and encourage the use of Raman spectroscopy for toxic element detection.

Methods for assessing biochemical oxygen demand (BOD): a review.

The Biochemical Oxygen Demand (BOD) is one of the most widely used criteria for water quality assessment. It provides information about the ready biodegradable fraction of the organic load in water. However, this analytical method is time-consuming (generally 5 days, BOD5), and the results may vary according to the laboratory (20%), primarily due to fluctuations in the microbial diversity of the inoculum used. Work performed during the two last decades has resulted in several technologies that are less time-consuming and more reliable. This review is devoted to the analysis of the technical features of the principal methods described in the literature in order to compare their performances (measuring window, reliability, robustness) and to identify the pros and the cons of each method.