Pollutant toxicity and detoxification by humic substances: mechanisms and quantitative assessment via luminescent biomonitoring

Abstract

The paper considers mechanisms of detoxification of pollutant solutions by water-soluble humic substances (HSs), natural detoxifying agents. The problems and perspectives of bioassay application for toxicity monitoring of complex solutions are discussed from ecological point of view. Bioluminescence assays based on marine bacteria and their enzymes are of special attention here; they were shown to be convenient tools to study the detoxifying effects on cellular and biochemical levels. The advantages of bioluminescent enzymatic assay for monitoring both integral and oxidative toxicities in complex solutions of model pollutants and HS were demonstrated. The efficiencies of detoxification of the solutions of organic oxidizers and salts of metals (including radioactive ones) by HS were analyzed. The dependencies of detoxification efficiency on time of exposure to HS and HS concentrations were demonstrated. Antioxidant properties of HS were considered in detail. The detoxifying effects of HS were shown to be complex and regarded as 'external' (binding and redox processes in solutions outside the organisms) and/or 'internal' organismal processes. The paper demonstrates that the HS can stimulate a protective response of bacterial cells as a result of (1) changes of rates of biochemical reactions and (2) stabilization of mucous layers outside the cell walls. Acceleration of auto-oxidation of NADH, endogenous reducer, by HS was suggested as a reason for toxicity increase in the presence of HS due to abatement of reduction ability of intracellular media.

Effect of low-dose ionizing radiation on luminous marine bacteria: radiation hormesis and toxicity

“…The examples of their physiological functions monitored during bioassay procedure are life-time, the rates of growth, movement, and respiration, as well as bioluminescent intensity. The main features of all classic bioassays are integral response and nonspecificity (Kudryasheva and Tarasova, 2015). As a result, the current approach to ecological investigations bases on the combination of chemical, radiometric, and biological methods that can provide complete information on the ecological state of a medium Deprezc et al, 2012;Tigini et al, 2011;Kudryasheva et al, 1998).…”

Low-intensity Exposures via Luminescent Bioassays of Different Complexity: Cells, Enzyme Reactions and Fluorescent Proteins

“…Figure 11. Antioxidant activity of humic substances was studied in [80][81][82][83][84] and fullerenols -in [84][85][86][87]. Cellular and enzymatic assays were used to evaluate a General Toxicity (GT) under conditions of the oxidative stress; this stress was modeled in the solutions of exogenous organic or inorganic oxidizers (1,4-benzoquinone or potassium ferricianide, respectively).…”

“…The latter appears in the presence of Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 21 August 2019 doi:10.20944/preprints201908.0221.v1exogenous oxidizers, depending on their redox potential and concentration[25]. Justification for GTand OxT application to evaluate toxicity of bioactive compounds is presented in[80][81][82][83][84][85][86][87].Principle of antioxidant efficiency evaluation is presented inFigure forbacteria-based (upper line) and enzyme-based (lower line) bioassays; humic substances are chosen here as an example of an antioxidant agent.…”

Is bacterial luminescence response to low-dose radiation associated with mutagenicity?

“…The simplicity of the registration procedure is beneficial because it enables researchers to conduct a large number of experiments under comparable conditions ensuring adequate statistical treatment of the results. For the last decades, bioluminescent bacteria-based assays have been widely applied for toxicity monitoring in water media including the effects of low-dose radiation (Roda et al, 2009;Girotti et al, 2008;Tarasova, 2015, Kudryasheva andRozhko, 2015).…”