Evaluating environmental impact of STP effluents on receiving water in Beijing by the joint use of chemical analysis and biomonitoring

Toxic responses of environmental concentrations of bifenthrin in larval freshwater snail Bellamya aeruginosa

Bifenthrin (BF) is ubiquitous in aquatic environments, and studies have indicated that environmental concentrations of BF could cause neurotoxicity and oxidative damage in fish and decrease the abundance of aquatic insects. However, little information is available on the toxicity of BF in freshwater benthic mollusks. Bellamya aeruginosa (B. aeruginosa) is a key benthic fauna species in aquatic ecosystems, and has extremely high economic and ecological values. In this study, larval B. aeruginosa within 24 h of birth were exposed to 0, 30 or 300 ng/L of BF for 30 days, and then the toxic effects from molecular to individual levels were comprehensively evaluated in all the three treatment groups. It was found that BF at 300 ng/L caused the mortality of snails. Furthermore, BF affected snail behaviors, evidenced by reduced crawling distance and crawling speed. The hepatopancreas of snails in the two BF exposure groups showed significant pathological changes, including increase in the number of yellow granules and occurrence of hemocyte infiltration, epithelial cell thinning, and necrosis. The levels of ROS and MDA were significantly increased after exposure to 300 ng/L BF, and the activities of two antioxidant enzymes SOD and CAT were increased significantly. GSH content decreased significantly after BF exposure, indicating the occurrence of oxidative damage in snails. Transcriptomic results showed that differentially expressed genes (DEGs) were significantly enriched in pathways related to metabolism and neurotoxicity (e.g., oxidative phosphorylation and Parkinson disease), and these results were consistent with those in individual and biochemical levels above. The study indicates that environmental concentration of BF results in decreased survival rates, sluggish behavior, histopathological lesions, oxidative damage, and transcriptomic changes in the larvae of B. aeruginosa. Thus, exposure of larval snails to BF in the wild at concentrations similar to those used in this study might have adverse consequences at the population level. These findings provide a theoretical basis for further assessing the ecological risk of BF to aquatic gastropods.

Modeling integrated biomarker response (IBR) index for the mussel Mytilus galloprovincialis (Lamark 1819) exposed to heavy metal mixture using the CCF design

Marine pollutants such as heavy metals (HMs) are considered among the most copious oxidative stress (OS) inducers in marine organisms which leads to reactive oxygen species (ROS) formation. Complementary to our previous bioassays studies, the present research focuses on Catalase (CAT), Glutathione S-transferase (GST) and Malondialdehyde (MDA) as oxidative stress biomarkers and the integrated biomarker response (IBR) indexes (IBR₁ and IBR₂) as an ecotoxicological assessment tool in Mytilus galloprovincialis using central composite face centered (CCF) design. The oxidative stress biomarkers were measured in adult mussels (45-55 mm) on 3 days-exposed under different sub-lethal concentrations of cadmium (Cd), zinc (Zn), and copper (Cu). Using multiple regressions, ANOVA analysis revealed that experimental data fitted to second-order (quadratic) polynomial equations. The results showed that types, concentrations and metals combinations has a direct effect in CAT and GST activities, MDA level and IBR indexes. Additionally, metal-metal interactions were found synergistic (supra-additive), antagonistic (infra-additive) or zero interaction in the toxicological effect. As necessary, the optimization of the experimental results was done in order to determine the optimal conditions for the oxidative stress responses and IBR indexes. It was demonstrated that the CCF design combined with the multi-biomarker approach and IBR index can be used as an appropriate tool in ecotoxicological modulation and prediction of oxidative stress and antioxidant status by heavy metals in the mussels Mytilus galloprovincialis.

Enhanced remediation of PAHs-contaminated site soil by bioaugmentation with graphene oxide immobilized bacterial pellets

Bioaugmentation is considered as a promising technology for cleanup of polycyclic aromatic hydrocarbons (PAHs) from contaminated site soil, however, available high-efficiency microbial agents remain very limited. Herein, we explored graphene oxide (GO)-immobilized bacterial pellets (JGOLB) by embedding high-efficiency degrading bacteria Paracoccus aminovorans HPD-2 in alginate-GO-Luria-Bertani medium (LB) composites. Microcosm culture experiments were performed with contaminated site soil to assess the effect of JGOLB on the removal of PAHs. The results showed that JGOLB exhibited greatly improved mechanical strength, larger specific surface area and more enriched mesopores, compared with traditional immobilized bacterial pellets. They significantly increased the removal rate of PAHs by 18.51% compared with traditional bacterial pellets, reaching the removal rate at 62.86% over 35 days of incubation. Moreover, the increase mainly focused on high-molecular-weight PAHs. JGOLB not only greatly increased the abundance of embedded degrading bacteria in soil, but also significantly enhanced the enrichment of potential indigenous degrading bacteria (Pseudarthrobacter and Arthrobacter), the functional genes involved in PAHs degradation and a number of ATP transport genes in the soil. Overall, such nanocomposite bacterial pellets provide a novel microbial immobilization option for remediating organic pollutants in harsh soil environment.

Diversity of endophytic bacteria in wild rice (Oryza meridionalis) and potential for promoting plant growth and degrading phthalates

Phthalates (PAEs) accumulated in agricultural soils and rice have increased human exposure risks. Microbial degradation could efficiently reduce the residue of organic pollutants in soil and crop plants. Here, we hypothesized that endophytic bacteria from wild rice have the potential for degradation of PAEs and plant growth promoting. The endophytic bacterial community and functional diversity in wild rice (Oryza meridionalis) were analyzed for the first time, and the potential for PAE degradation and plant growth promoting by endophytes were investigated. The results of Illumina high-throughput sequencing revealed that abundant endophytes inhabited in wild rice with Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria being the dominant phyla. Endophytic bacterial diversity and complexity were confirmed by isolation and clustering of isolates. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that endophytes exerted diverse functions such as plant growth promoting, xenobiotics biodegradation, pollution remediation and bacterial chemotaxis. Pure culture experiment showed that 30 isolated endophytic strains exhibited in vitro plant growth promoting activities, and rice plants inoculated with these strains confirmed their growth promoting abilities. Some endophytic strains were capable of efficiently degrading PAEs, with the highest removal percentage of di-n-butyl phthalate (DBP) up to 96.1% by Bacillus amyloliquefaciens strain L381 within 5 days. Synthetic community F and strain L381 rapidly removed DBP from soil (removing 91.0%-99.2% within 10 d and from rice plant slurry (removing 93.4%-99.2% within 5 d). These results confirmed the hypothesis and demonstrated the diversity of endophytic bacteria in wild rice with diverse functions, especially for plant growth promoting and removing PAEs. These multifunctional endophytic bacteria provided good alternatives to reduce PAE accumulation in crops and increase yield.