Escalating anthropogenic activities have caused heavy metal contamination in the environmental matrices. Due to their recalcitrant and toxic nature, their occurrence in high titers in the environment can threaten survival of biotic components. To take the edge off, remediation of metal-contaminated sites by phytoremediators that exhibit a potential to withstand heavy metal stress and quench harmful metals is considered an eco-sustainable approach. Despite the enormous potential, phytoremediation technique suffers a setback owing to high metal concentrations, occurrence of multiple pollutants, low plant biomass, and soil physicochemical status that affect plants at cellular and molecular levels, inducing morphological, physiological, and genetic alterations. Nevertheless, augmentation of soil with microorganisms can alleviate the challenge. A positive nexus between microbes, particularly plant growth-promoting microorganisms (PGPMs), and phytoremediators can prevent phytotoxicity and augment phytoremediation by employing strategies such as production of secondary metabolites, solubilization of phosphate, and synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and phytohormones. Microbes can mediate tolerance in plants by fortifying their antioxidant machinery, which maintains redox homeostasis and alleviates metal-induced oxidative damage in the plants. Associated microbes can also activate stress-responsive genes in plants and abridge metal-induced toxic effects. An in-depth exploration of the mechanisms employed by plant-associated microbes to trigger tolerance in phytoremediators is crucial for improving their phytoremediation potential and real-world applications. The present article attempts to comprehensively review these mechanisms that eventually facilitate the development of improved/new technology for soil ecosystem restoration.

Heavy metals (HM) are toxic to the microbiota of agricultural soils because they affect the development of bacteria and fungi that promote plant growth and are agents of biological control of pathogenic organisms. In this regard, fungi ofthe genus Trichoderma have these functions in plants, but like other organisms, HM affects their growth and biological activity. This article reviews the lithogenic and anthropogenic sources of generation of HM Cu, Cr-VI, Pb, and Cd, the tolerance mechanisms, and the antioxidant response to oxidative damage in Trichoderma caused by HM. It was identified that in some agricultural soils, the HM content increases mainly due to irrigation with wastewater and the intensive use of agrochemicals, such as pesticides and fertilizers. In Trichoderma, the tolerance mechanisms to Cu, Cr-VI, Pb, and Cd include biosorption, bioaccumulation, and biotransformation. In contrast, studies of the antioxidant response of Trichoderma to oxidative stress caused by MP are scarce. In the case of Cu and Cr, a relationship between changes in antioxidant enzyme activity and a decrease in the oxidation of cell membrane lipids is reported. This represents an opportunity to understand the toxic effect of MP on fungi of the genus Trichoderma, which is part of the biotic soil community.

The persistent presence of arsenic (As) pollution in soils worldwide poses a significant threat to human and environmental health, highlighting the urgent need for effective remediation strategies. Therefore, this study aims to evaluate the capacity of the Rhizopus microsporus Os4 fungal strain, to remove As from contaminated media in laboratory studies. R. microsporus Os4 was isolated from soils of a recreation area of Concepci & oacute;n del Oro, Zacatecas, M & eacute;xico, where As concentrations ranged from 146.56 to 11,233.81 mg Kg(-1). Os4 was grown in a culture medium with arsenic V (As(V)), and strain resistance was determined at concentrations up to 15,000 mg L-1. In removal assays using a liquid medium with 7,000 mg L-1, Os4 was capable of reducing 90% of the As(V) concentration after 7 days. To determine whether arsenic has an impact on fungal cell walls, Fourier Transform Infrared Spectroscopy analysis was performed, confirming the presence of functional groups in mycelium cell walls with the ability to facilitate the biosorption of arsenic mycelium cell walls. Scanning Electron Microscopy confirmed surface damage and cell morphology changes a response to cell stress induced by contact with As(V). These findings indicate that R. microsporus Os4 employs a biosorption mechanism on the cell wall for arsenic removal, suggesting its potential application in the bioremediation of arsenic-contaminated soils.

Current research was performed to look for the performance of Bacillus cereus PY3 for metal detoxification. Strain PY3 was recognized as B. cereus using 16 S rRNA. Higher rate of removal of Zn and Cr (VI) by PY3 was obtained between pH 6-8 and 100-500 mu g/mL in 24 h. Highest removal of Cr6+ by strain PY3 was achieved at acidic, neutral, and alkaline atmosphere, 100-300 mu g Cr6+/mL and 25-35 degrees C. Supernatant of PY3 detoxified Cr6+ into Cr3+ then cell pellet (debris) adsorbed them. The mechanism of metal removal was due to the release of cytolic extracts. Release of antioxidants and bio-film played a protective role against cell damage. Metals increased antioxidants and bio-film formation. SEM images showed the smooth external structure of PY3 when cells were exposed to metals thus confirming the role of cells for detoxification. Results Above facts conclude that PY3 can remove metallic pollution in polluted soil.