Evaluation of the efficiency of chlorpyrifos-ethyl remediation by Methylobacterium radiotolerans and Microbacterium arthrosphaerae using response of some biochemical biomarkers

Heavy Metal Pollution in the Environment and Its Impact on Health: Exploring Green Technology for Remediation

Along with expanding urbanization and industrialization, environmental pollution which negatively affects the surroundings, has been rising quickly. As a result, induces heavy metal contamination which poses a serious threat to living organisms of aquatic and soil ecosystems. Therefore, they are a need to ameliorate the effects cost by cost pollution on the environment. In this review, we explore methods employed to mitigate the effects caused by heavy metals on the environment. Many techniques employed to manage environmental pollution are tedious and very costly, necessitating the use of alternative management strategies to resolve this challenge. In this concept, bioremediation is viewed as a future technique, due to its environmental friendliness and cost-effective measures aligned with sustainable or climate-smart agriculture to manage contaminants in the environment. The technique involves the use of living entities such as bacteria, fungi, and plants to deteriorate toxic substances from the rhizosphere. Currently, bioremediation is thought to be the most practical, dependable, environmentally benign, and long-lasting solution. Although bioremediation involves different techniques, they are still a need to find the most efficient method for removing toxic substances from the environment. This review focuses on the origins of heavy metal pollution, delves into cost-effective and green technological approaches for eliminating heavy metal pollutants from the environment, and discusses the impact of these pollutants on human health.

Role of plant growth-promoting rhizobacteria in boosting the phytoremediation of stressed soils: Opportunities, challenges, and prospects

Soil is considered as a vital natural resource equivalent to air and water which supports growth of the plants and provides habitats to microorganisms. Changes in soil properties, productivity, and, inevitably contamination/stress are the result of urbanisation, industrialization, and long-term use of synthetic fertiliser. Therefore, in the recent scenario, reclamation of contaminated/stressed soils has become a potential challenge. Several customized, such as, physical, chemical, and biological technologies have been deployed so far to restore contaminated land. Among them, microbial-assisted phytoremediation is considered as an economical and greener approach. In recent decades, soil microbes have successfully been used to improve plants' ability to tolerate biotic and abiotic stress and strengthen their phytoremediation capacity. Therefore, in this context, the current review work critically explored the microbial assisted phytoremediation mechanisms to restore different types of stressed soil. The role of plant growth-promoting rhizobacteria (PGPR) and their potential mechanisms that foster plants' growth and also enhance phytoremediation capacity are focussed. Finally, this review has emphasized on the application of advanced tools and techniques to effectively characterize potent soil microbial communities and their significance in boosting the phytoremediation process of stressed soils along with prospects for future research.

Pendimethalin biodegradation by soil strains of Burkholderia sp. and Methylobacterium radiotolerans

Pendimethalin herbicide is widely used and persists in the environment as a contaminant causing negative impacts, including for human health. Microorganisms have the capacity to remove many contaminants from the environment. Thus, the aim of this work was to evaluate the efficiency of soil bacterial species prospected by molecular modelling of cytochrome P450 in to degrade pendimethalin. Strains of Burkholderia sp. and Methylobacterium radiotolerans were cultivated in a mineral saline medium enriched with 281 mg/L pendimethalin (MSPEN) and another containing glucose 1.0 g/L as extra carbon source (MSPENGLI). Both strains were able to degrade pendimethalin under the two conditions experienced. Burkholderia sp. F7G4PR33-4 was more efficient in degrading 65% of the herbicide in MSPEN medium, with 49.3% in MSPENGLI; while Methylobacterium radiotolerans A6A1PR46-4 degraded 55.4% in MSPEN and 29.8% in MSPENGLI mediums. These findings contribute to the expansion of knowledge on the competence of isolates of these two bacterial genera in degrading herbicidal xenobiotics and biotechnological potential for pendimethalin degradation and bioremediation.

Combined biostimulation and bioaugmentation for chlorpyrifos degradation in laboratory microcosms

Chlorpyrifos (CP) is a persistent organophosphorus pesticide (OP) used in soil ecosystem for insect control. Bioremediation process has been proven promising in degrading these toxic molecules and restoring the physio-chemical properties of soil. This work reports a laboratory microcosm study in both non-sterile & sterile conditions, conducted over a period of 56 days to examine the combined effect of additional supplements like biostimulants (BSs) such as N, P, and K in the presence of suitable carrier materials (compost, wheat straw, and corncob) along with bioaugmentation by a Ochrobactrum sp. CPD-03 on CP degradation from the contaminated soil. CP degradation was thoroughly monitored at an interval of 7 days over a period of 56 days. Results showed biostimulation and bioaugmentation along with compost as carrier material had shown higher CP degradation efficiency of 76 ± 2.8 and 74 ± 1.6% in non-sterile and sterile microcosms over a period of 56 days. Moreover, bacterial community profiling (16s rRNA and opd gene) demonstrated increased microbial counts, corroborating the efficiency of the bioremediation process. The survival of CPD-03 at the end of the assay validated its ability of colonizing modified soils. By this integrated method with compost as carrier material, bioremediation process could be enhanced for restoration CP-contaminated soils.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02980-9.

Acute toxicity and biomarker responses in Gammarus locusta amphipods exposed to copper, cadmium, and the organochlorine insecticide dieldrin

The toxicity of copper, cadmium, and dieldrin in adult Gammarus locusta (a marine amphipod) is currently unclear. Thus, G. locusta from the North Lake of Tunis were subjected to acute toxicity tests to assess LC50s at 48-96 h and to biomarker response tests through the assessment of catalase and acetylcholinesterase activities and malondialdehyde levels. The present study demonstrated the abilities of a chlorinated hydrocarbon pesticide (dieldrin) induce to oxidative stress and neurotoxicity. The comparison of metal toxicity showed that G. locusta was more sensitive to cadmium than copper. The three stressors caused significant inductions of all three biomarkers in a concentration-dependent manner. Catalase induction was dependent on exposure duration for all pollutants, while only copper led to increased malondialdehyde with longer exposure times. Catalase induction and malondialdehyde increase appeared to be sex dependent for all three pollutants. The neurotoxic effects of the pollutants were concentration dependent according to inhibition of acetylcholinesterase activity. In conclusion, catalase, malondialdehyde, and acetylcholinesterase are efficient biomarkers of copper, cadmium, and dieldrin in G. locusta.