Luminescent Microbial Bioassays and Microalgal Biosensors as Tools for Environmental Toxicity Evaluation

Abstract

This chapter deals with toxicity bioassays and biosensors based on luminescent microorganisms that report on global toxicity of a sample in such a way that luminescence is reduced or inhibited in the presence of toxic compounds that impair metabolism. Both natural as well as recombinant microorganisms are considered. A detailed description of their main characteristics and environmental applications is reported. A few examples of bioassays for detecting oxidative stress (both bioluminescent and fluorescent bioreporters) are also mentioned and discussed as reactive oxygen species (ROS) formation and subsequent oxidative stress if the antioxidant defenses of the cells are surpassed is one of the main mechanisms of toxicity for most pollutants.There is also a section dedicated to microalgal-based biosensors given their ecological relevance as primary producers, their easiness of culture and immobilization in different matrices, ability to acclimate to low nutrients conditions and ubiquity in aquatic environments. The most used toxicity endpoints for this type of biosensors are the alteration of photosynthetic activity (optical and amperometric biosensors) and the inhibition of enzymes such as alkaline phosphatase (APA) or sterases (mostly conductometric biosensors). The main information is shown in tables that include the microorganisms, their main characteristics (reporter gene systems, transducer types for biosensors) and their main environmental applications as well as relevant references.Although some of these bioassays have already been standardized by different international organizations, there are still many which are also promising tools for environmental global toxicity evaluation and should be fully validated and standardized for regulatory purposes.

Use of Cyanobacterial Luminescent Bioreporters to Report on the Environmental Impact of Metallic Nanoparticles

“…As oxidative stress is one of the mechanisms of action most observed in organisms after the exposure to metallic NPs, many studies have been performed in a variety of cell lines to describe it. To date, several studies about metallic NPs toxicity using bioluminescence bioreporters exist, however only a few of them have investigated metallic NPs ROS production [48]. Most of them have been performed with Escherichia coli or Pseudomonas based bioreporters thus, there are not any study in the literature concerning the detection of ROS produced by metallic NPs on organisms of environmental relevance such as cyanobacteria.…”

Ecotoxicity assessment of microcystins from freshwater samples using a bioluminescent cyanobacterial bioassay

“…Prior to this study, several authors have used the well stablished bioluminescence bioassay based on Aliivibrio fischeri (a naturally bioluminescent marine bacterium, formerly known as Vibrio fischeri) (Maršálek and Bláha, 2000;D'ors et al, 2012;Prasath et al, 2019). However, there are conflicting results regarding the suitability of A. fischeri to report on toxicity of cyanotoxins (Maršálek and Bláha, 2000), and also the use of marine organisms to test freshwater samples present some problems related to the high saline concentrations that are necessary in the analyte during the assay (Rodea-Palomares et al, 2009a;Hurtado-Gallego et al, 2019). Salinity may alter, among other parameters, the solubility of organic compounds.…”