Toxicity of five anilines to crustaceans, protozoa and bacteria

Aromatic amines (anilines and related derivates) are an important class of environmental pollutants that can be released to the aquatic environment as industrial effluents or as breakdown products of pesticides and dyes. The toxicity of aniline, 2-chloroaniline, 3-chloroaniline, 4-chloroaniline and 3,5-dichloroaniline towards a multitrophic test battery comprised of bacteria Aliivibrio fischeri (formerly Vibrio fischeri), a ciliated protozoan Tetrahymena thermophila and two crustaceans (Daphnia magna and Thamnocephalus platyurus) were investigated. Under the applied test conditions, the toxicity of the anilines notably varied among the test species. The bacteria and protozoa were much less sensitive towards the anilines than the crustaceans: EC50 values 13–403 mg L-1 versus 0.13–15.2 mg L-1. No general tendency between toxicity and the chemical structure of the anilines (the degree of chloro-substitution and the position of the chloro-substituents) was found in the case of all the tested aquatic species. The replacement of the artificial test medium (ATM) by the river water remarkably decreased the toxicity of anilines to crustaceans but not to protozoa. This research is part of the EU 6th Framework Integrated Project OSIRIS, in which ecotoxicogenomic studies of anilines (e.g., for Daphnia magna) will also be performed that may help to clarify the mechanisms of toxicity of different anilines

LuxCDABE—Transformed Constitutively Bioluminescent Escherichia coli for Toxicity Screening: Comparison with Naturally Luminous Vibrio fischeri

We show that in vitro toxicity assay based on inhibition of the bioluminescence of recombinant Escherichia coli encoding thermostable luciferase from Photorhabdus luminescens is a versatile alternative to Vibrio fischeri Microtox™ test. Performance of two luxCDABE-transformed E. coli MC1061 constructs (pDNlux) and (pSLlux) otherwise identical, but having 100-fold different background luminescence was compared with the performance of V. fischeri. The microplate luminometer and a kinetic Flash-Assay test format was used that differently from Microtox test is also applicable for high throughput analysis. Toxic effects (30-s till 30-min EC50) of four heavy metals (Zn, Cd, Hg, Cu) and three organic chemicals (aniline, 3,5-dichloroaniline and 3,5-dichlorophenol) were studied. Both E. coli strains had comparable sensitivity and the respective 30-min EC50 values highly correlated (log-log R2 = 0.99; p < 0.01) showing that the sensitivity of the recombinant bacteria towards chemicals analyzed did not depend on the bioluminescence level of the recombinant cells. The most toxic chemical for all used bacterial strains (E. coli, V. fischeri) was mercury whereas the lowest EC50 values for Hg (0.04–0.05 mg/L) and highest EC50 values for aniline (1,300–1,700 mg/L) were observed for E. coli strains. Despite of that, toxicity results obtained with both E. coli strains (pSLlux and pDNlux) significantly correlated with V. fischeri results (log-log R2 = 0.70/0.75; p < 0.05/0.01). The use of amino acids (0.25%) and glucose (0.05%)-supplemented M9 medium instead of leucine-supplemented saline significantly (p < 0.05) reduced the apparent toxicity of heavy metals to both E. coli strains up to three orders of magnitude, but had little or no complexing effect on organic compounds. Thus, P. luminescens luxCDABE-transformed E. coli strains can be successfully used for the acute toxicity screening of various types of organic chemicals and heavy metals and can replace V. fischeri in certain cases where the thermostability of luciferase >30 °C is crucial. The kinetic Flash Assay test format of the bioluminescence inhibition assay facilitates high throughput analysis. The assay medium, especially in case of testing heavy metals should be a compromise: optimal for the viability/luminescence of the recombinant test strain and of minimum complexing potential

Atomic layer deposition of titanium oxide films on As-synthesized magnetic Ni particles : Magnetic and safety properties

Spherical nickel particles with size in the range of 100-400 nm were synthesized by non-aqueous liquid phase benzyl alcohol method. Being developed for magnetically guided biomedical applications, the particles were coated by conformal and antimicrobial thin titanium oxide films by atomic layer deposition. The particles retained their size and crystal structure after the deposition of oxide films. The sensitivity of the coated particles to external magnetic fields was increased compared to that of the uncoated powder. Preliminary toxicological investigations on microbial cells and small aquatic crustaceans revealed non-toxic nature of the synthesized particles.Peer reviewe

Ecotoxicity profiling of a library of 24 l-phenylalanine derived surface-active ionic liquids (SAILs)

We evaluated the ecotoxicity of a library of 24 L-phenylalanine derived surface-active ionic liquids (SAILs) with various cationic head groups (pyridinium, Py; imidazolium, Imid and cholinium, Chol) and alkyl ester chains from C-2 to C-16. For toxicity evaluation we used 72-h algal growth inhibition assay (OECD 201) with Raphidocelis subcapitata and 24-h mortality test with aquatic crustaceans Thaninocephalus platyurus (ISO 14380:2011). The OECD 201 assay was applied to all 24 SAILs while the ISO 14380:2011 test was applied to a subset, specifically all eight pyridinium SAILs and C-6 and C-8 examples of the imidazolium and cholinium SAILs (total 12 SAILs). For the comparison, 30-min EC50 data (based on inhibition of bioluminescence) previously reported by this group for the 24 SAILs for marine bacteria Vibrio fischeri (ISO 21338:2010) were included and correlated to the algae and aquatic crustaceans data. According to the results of the multritrophic test battery only two studied SAILs - PyC2 and CholC(2) - could be considered 'low toxicity', (i.e. were ranked not harmful, L(E)C-50 > 100 mg/L by the most sensitive test - algal growth inhibition assay). T. platyurus proved about 100-times more tolerant to studied SAILs than algae. An alternative classification scale dependent on the average MW of the compound dataset (based on molar concentrations and not concentrations based on mg/L) was suggested to rank the compounds. When compared to the classification scale independent of the MW of the compound, a more accurate appraisal was achieved for suggesting the greener alternatives for certain commercial SAILs/surfactants

ANTIBACTERIAL ACTIVITY OF 24 L-PHENYLALANINE DERIVED SURFACE-ACTIVE IONIC LIQUIDS (SAILS) TOWARDS TWO CLINICALLY RELEVANT PATHOGENS

Ionic liquids - low melting point salts - are attractive for a wide range of applications, from material science to medicinal chemistry. The vast number of possible combinations of different cations and anions enables researchers to fine-tune the physico-chemical and/or biological properties (e.g., hydrophobicity or toxicity). This paper systematically analyses the antimicrobial potency of a library of 24 L-phenylalanine derived surface-active ionic liquids (SAILs; C2-C16) and provides EC50, MIC and MBC values for these compounds towards two clinically relevant pathogenic bacterial models – Escherichia coli and Staphylococcus aureus using standard broth microdilution method ISO 20776-1:2006. We demonstrated that the antimicrobial potency of SAILs containing different cationic headgroups (pyridinium, imidazolium, and cholinium) increased with the length of the alkyl ester chain from C2 to C12 and then similar values obtained for C14 followed by a decreased toxicity for C16. This trend was not dependent on the type of headgroup. The minimum inhibitory concentration (MIC) ranged from 8000 mg/L (C2 SAILs) down to 4 mg/L (C12 SAILs). Most potent were C12 SAILs that inhibited the growth of S. aureus and E. coli at concentration of few milligrams per liter: EC50 values ~2 and ~15 mg/L (or ~4 and ~27 μM), respectively. These data are comparable to the antimicrobial efficiency of benzalkonium chloride, which is widely used antimicrobial compound. As a rule, gram-positive S. aureus was 7-fold more susceptible to the SAILs than gram-negative E. coli. In addition, the results obtained in this study on medically relevant bacteria were in agreement with our previous data on Vibrio fischeri – a naturally luminescent marine bacterium. We hypothesize that the toxic effects of studied SAILs was manifested via disturbing the bacterial membranes. To summarise, the SAILs are promising antimicrobials which toxicity towards bacteria can be tuned by modifying the alkyl ester chain properties

Toxicity of Nine (Doped) Rare Earth Metal Oxides and Respective Individual Metals to Aquatic Microorganisms Vibrio fischeri and Tetrahymena thermophila

Despite the increasing use of rare earth elements (REEs) and oxides (REOs) in various technologies, the information on their ecotoxicological hazard is scarce. Here, the effects of La3+, Ce3+, Pr3+, Nd3+, Gd3+, CeO2, and eight doped REOs to marine bacteria Vibrio fischeri and freshwater protozoa Tetrahymena thermophila were studied in parallel with REO dopant metals (Co2+, Fe3+, Mn2+, Ni2+, Sr2+). The highest concentrations of REOs tested were 100 mg/L with protozoa in deionized water and 500 mg/L with bacteria in 2% NaCl. Although (i) most REOs produced reactive oxygen species; (ii) all studied soluble REEs were toxic to bacteria (half-effective concentration, EC50 3.5–21 mg metal/L; minimal bactericidal concentration, MBC 6.3–63 mg/L) and to protozoa (EC50 28–42 mg/L); and (iii) also some dopant metals (Ni2+, Fe3+) proved toxic (EC50 ≤ 3 mg/L), no toxicity of REOs to protozoa (EC50 &gt; 100 mg/L) and bacteria (EC50 &gt; 500 mg/L; MBC &gt; 500 mg/L) was observed except for La2NiO4 (MBC 25 mg/L). According to kinetics of V. fischeri bioluminescence, the toxicity of REEs was triggered by disturbing cellular membrane integrity. Fortunately, as REEs and REOs are currently produced in moderate amounts and form in the environment insoluble salts and/or oxides, they apparently present no harm to aquatic bacteria and protozoa

Plasma membrane is the target of rapid antibacterial action of silver nanoparticles in Escherichia coli and Pseudomonas aeruginosa

This work was supported by Estonian Research Council grants IUT23-5 and PUT1015 and by Research Council of Lithuania, funding grant no MIP-040/2015Silver nanoparticles (AgNP) are widely used in consumer products and in medicine, mostly due to their excellent antimicrobial properties. One of the generally accepted antibacterial mechanisms of AgNP is their efficient contact with cells and dissolution in the close vicinity of bacterial cell envelope. Yet, the primary mechanism of cell wall damage and the events essential for bactericidal action of AgNP are not elucidated. Materials and methods: In this study we used a combination of various assays to differentiate the adverse effects of AgNP on bacterial cell envelope: outer membrane (OM) and plasma membrane (PM). Results: We showed that PM was the main target of AgNP in gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa: AgNP depolarized PM, induced the leakage of the intracellular K+, and inhibited cellular respiration. The results of bacterial bioluminescence inhibition assay in combination with AgNP dissolution and oxidation assays demonstrated that the adverse effects of AgNP occurred at concentrations 7–160 µM. These toxic effects occurred already within the first few seconds of contact of bacteria and AgNP and were driven by dissolved Ag+ ions targeting bacterial PM. However, the irreversible inhibition of bacterial growth detected after 1-hour exposure occurred at 40 µM AgNP for P. aeruginosa and at 320 µM AgNP for E. coli. In contrast to effects on PM, AgNP and Ag+ ions had no significant effect on the permeability and integrity of bacterial OM, implying that AgNP indeed targeted mainly PM via dissolved Ag+ ions. Conclusion: AgNP exhibited antibacterial properties via rapid release of Ag+ ions targeting the PM and not the OM of gram-negative bacteriaBiochemijos katedraGamtos mokslų fakultetasVytauto Didžiojo universiteta