Evaluation of glutathione S-transferase activity as a biomarker of PAH pollution in mudskipper, Boleophthalmus dussumieri, Persian Gulf

Aerobic Metabolism Impairment in Tambaqui (Colossoma macropomum) Juveniles Exposed to Urban Wastewater in Manaus, Amazon

The main purpose of the present study was to investigate the potential use of metabolic parameters as non-specific biomarkers of pollution. The Igarapé do Quarenta is a small urban river crossing an industrial area in the city of Manaus, Amazon, and receives the city wastewater without treatment. The fish tambaqui (Colossoma macropomum) were exposed to water collected from two different sites of that stretch for 96 h. After exposure, routine metabolic rate (RMR) was measured, and fish were euthanized for measurements of electron transport system (ETS) activity, Copper (Cu) and Cadmium (Cd) bioaccumulation and biliary PAHs. Water in the sampling points presented low oxygen and high pH, conductivity, dissolved ions, Cu, Cd and ammonia. Bile concentrations of PAHs were high suggesting industrial pollution. The tambaqui exposed to water from Igarapé do Quarenta showed increased RMR and decreased ETS/RMR suggesting impairment of metabolic fish performance and the potential use of these parameters as biomarkers.

Acute toxicity, bioconcentration, elimination, action mode and detoxification metabolism of broflanilide in zebrafish, Danio rerio

Broflanilide, a novel meta-diamide insecticide, shows high insecticidal activity against agricultural pests and is scheduled to be launched onto the market in 2020. However, little information about its potential toxicological effects on fish has been reported. In this study, broflanilide showed low toxicity to the zebrafish, Danio rerio, with LC₅₀ > 10 mg L^-1 at 96 h and also did not inhibit GABA-induced currents of the heteromeric Drα1β2Sγ2 GABA receptor. Broflanilide showed medium bioconcentration level with a bioconcentration factor at steady state (BCF_ss) of 10.02 and 69.40 in D. rerio at 2.00 mg L^-1 and 0.20 mg L^-1, respectively. In the elimination process, the concentration of broflanilide rapidly decreased within two days and slowly dropped below the limit of quantification after ten days. In the 2.00 mg L^-1 broflanilide treatment, CYP450 activity was significantly increased up to 3.11-fold during eight days. Glutathione-S- transferase (GST) activity significantly increased by 91.44 % within four days. In conclusion, the acute toxicity of broflanilide was low, but it might induce chronic toxicity, affecting metabolism. To our knowledge, this is the first report of the toxicological effects of broflanilide on an aquatic organism, which has the potential to guide the use of broflanilide in the field.

Polycyclic aromatic hydrocarbons (PAHs) and some biomarkers in the green sea turtles (Chelonia mydas)

Selected blood biochemical parameters (Glutathione S transferase: GST; Alanine aminotransferase: ALT; Aspartate aminotransferase: AST; Lactate dehydrogenase: LD and glucose) and polycyclic aromatic hydrocarbons (PAHs) were measured in blood samples from 18 green sea turtles (Chelonia mydas) from the Iranian coastline on the northern shore of the Sea of Oman. Mean total PAH concentration in the blood samples was 17.802 ± 1.006 ng/gdw. The study found no significant correlation between blood biochemical parameters and PAHs (p > 0.01), however significant correlations were found between total PAHs and GST activity (p < 0.01). The GST activity measured in this study was useful as a first investigation into the biological effects of PAH pollution as well as in determining the bioavailability of pollution. The results suggest that PAHs might be a factor influencing a reduction in green sea turtle egg fertilization and hatching success. Further study is needed concerning the effects of PAHs and other pollutants on green sea turtles, and specifically on the potential impact on the fetal development of green sea turtles.

Toxicity and Mechanisms of Action of Polycyclic Aromatic Hydrocarbon Pollution in Red Algae (Gracilaria corticata) from the Northern Coast of the Oman Sea

The activities of selected biomarkers including 7-ethoxycoumarin-O-deethylase (ECOD) and glutathione S-transferase (GST) were measured in the red algae (Gracilaria corticata) obtained from the Oman Sea. Chemical analyses were used to assess the polycyclic aromatic hydrocarbons (PAHs) in the red algae. Total PAH concentrations in the red algae ranged from 3.61 to 8.14 ng g^-1 dry weight. Mean GST and ECOD activity also varied from 8.87 to 15.32 nmol/mg protein/min and from 0.31 to 1.02 pmol/min/mg protein, respectively. Significant correlations were found between the total PAH levels and the selected biomarkers (p < 0.01). The results showed that ECOD and GST enzymes reacted to PAHs in phase I and II detoxification mechanisms of red algae (G. corticata), which extend the use of these biomarkers for investigation of the biological effects of PAH pollution as well as determination of pollution bioavailability. Environ Toxicol Chem 2019;38:1947-1953. © 2019 SETAC.

Homologous Recombination in Core Genomes Facilitates Marine Bacterial Adaptation

Acquisition of ecologically relevant genes is common among ocean bacteria, but whether it has a major impact on genome evolution in marine environments remains unknown. Here, we analyzed the core genomes of 16 phylogenetically diverse and ecologically relevant bacterioplankton lineages, each consisting of up to five genomes varying at the strain level. Statistical approaches identified from each lineage up to ∼50 loci showing anomalously high divergence at synonymous sites, which is best explained by recombination with distantly related organisms. The enriched gene categories in these outlier loci match well with the characteristics previously identified as the key phenotypes of these lineages. Examples are antibiotic synthesis and detoxification in Phaeobacter inhibens, exopolysaccharide production in Alteromonas macleodii, hydrocarbon degradation in Marinobacter hydrocarbonoclasticus, and cold adaptation in Pseudoalteromonas haloplanktis Intriguingly, the outlier loci feature polysaccharide catabolism in Cellulophaga baltica but not in Cellulophaga lytica, consistent with their primary habitat preferences in macroalgae and beach sands, respectively. Likewise, analysis of Prochlorococcus showed that photosynthesis-related genes listed in the outlier loci are found only in the high-light-adapted ecotype and not in the low-light adapted ecotype. These observations strongly suggest that recombination with distant relatives is a key mechanism driving the ecological diversification among marine bacterial lineages.IMPORTANCE Acquisition of new metabolic genes has been known as an important mechanism driving bacterial evolution and adaptation in the ocean, but acquisition of novel alleles of existing genes and its potential ecological role have not been examined. Guided by population genetic theories, our genomic analysis showed that divergent allele acquisition is prevalent in phylogenetically diverse marine bacterial lineages and that the affected loci often encode metabolic functions that underlie the known ecological roles of the lineages under study.

Combined toxicity of endosulfan and phenanthrene mixtures and induced molecular changes in adult Zebrafish (Danio rerio)

Individual and combined toxicities of endosulfan (ENDO) with phenanthrene (PHE) were evaluated using zebrafish (Danio rerio) adults. The 96-h LC₅₀ values for ENDO and PHE were 4.6 μg L^-1 and 920 μg L^-1, respectively. To evaluate the mixture toxicity, LC₁₀ and LC₅₀ concentrations were grouped into four combinations as ENDO-LC₁₀ + PHE-LC₁₀, ENDO-LC₁₀ + PHE-LC₅₀, ENDO-LC₅₀ + PHE-LC₁₀, and ENDO-LC₅₀ + PHE-LC₅₀, and their acute toxicities were determined. The combination of LC₅₀-ENDO and LC₁₀-PHE exhibited a synergistic effect. In addition, acetylcholinesterase activity decreased in zebrafish bodies exposed to ENDO with or without PHE. Combined treatments induced higher glutathione S-transferase activity compared to individual treatments. Carboxylesterase activity increased in both heads and bodies of ENDO-treated fishes compared with PHE-treated fishes. Using RT-qPCR technique, CYP1A gene expression significantly up-regulated in all combinations, whereas CYP3A was unchanged, suggesting that enzymes involved in defense may play different roles in the detoxification. CYP7A1 gene responsible for bile acid biosynthesis is dramatically down-regulated after exposure to the synergistic combination exposure, referring that the synergistic effect may be resulted from the reduction of bile production in zebrafishes. Among gender-related genes, CYP11A1 and CYP17A1 genes in female zebrafish decreased after treatment with ENDO alone and combination of LC₅₀-ENDO and LC₁₀-PHE. This might be related to a reduction in cortisol production. The overall results indicated that ENDO and PHE were toxic to zebrafish adults both individually and in combination, and that their co-presence induced changes in the expression of genes responsible for metabolic processes and defense mechanisms.