Unraveling the Underlying Heavy Metal Detoxification Mechanisms of Bacillus Species

Abstract

The rise of anthropogenic activities has resulted in the increasing release of various contaminants into the environment, jeopardizing fragile ecosystems in the process. Heavy metals are one of the major pollutants that contribute to the escalating problem of environmental pollution, being primarily introduced in sensitive ecological habitats through industrial effluents, wastewater, as well as sewage of various industries. Where heavy metals like zinc, copper, manganese, and nickel serve key roles in regulating different biological processes in living systems, many heavy metals can be toxic even at low concentrations, such as mercury, arsenic, cadmium, chromium, and lead, and can accumulate in intricate food chains resulting in health concerns. Over the years, many physical and chemical methods of heavy metal removal have essentially been investigated, but their disadvantages like the generation of chemical waste, complex downstream processing, and the uneconomical cost of both methods, have rendered them inefficient,. Since then, microbial bioremediation, particularly the use of bacteria, has gained attention due to the feasibility and efficiency of using them in removing heavy metals from contaminated environments. Bacteria have several methods of processing heavy metals through general resistance mechanisms, biosorption, adsorption, and efflux mechanisms. Bacillus spp. are model Gram-positive bacteria that have been studied extensively for their biosorption abilities and molecular mechanisms that enable their survival as well as their ability to remove and detoxify heavy metals. This review aims to highlight the molecular methods of Bacillus spp. in removing various heavy metals ions from contaminated environments.

Bacterial Biosorbents, an Efficient Heavy Metals Green Clean-Up Strategy: Prospects, Challenges, and Opportunities

“…Among them, Bacillus sp. is considered a potential agent for removing various HMs, especially Gram-positive bacteria [ 23 ]. Oves et al investigated Bacillus thuringiensis OSM269 that was tolerant to various concentrations (25–150 mg/L) of HMs, such as Cd, Cr, Cu, Pb, and Ni [ 24 ].…”

Harnessing the Potential of Bacillus altitudinis MT422188 for Copper Bioremediation

“… General aspects of copper metabolism in bacterial cells, where it acts as a causative agent for copper-mediated oxidative stress ( Ladomersky and Petris, 2015 ), non-oxidative stress, its efflux ( Alotaibi et al, 2021 ), its major functions ( Bondarczuk and Piotrowska-Seget, 2013 ) in the cell as well as how a cell protects ( Giachino and Waldron, 2020 ) itself from its harmful effects. The conversion of Cu 2+ to Cu + results in the production of ·OH ions, which damages the cells.…”

“…During efflux mechanism, CopZ acts as chaperone and converts Cu 2+ to Cu + which ultimately enters the cells via CopA protein. CopB protein is associated with ATPase which is energy dependent and helps in Cu + efflux out of the cell ( Alotaibi et al, 2021 ; Figure 10 ). To the best of our knowledge, copper sequestration by MTs as well as uptake and efflux mechanisms regulated by copZA operon are apparently involved in copper homeostasis in B. altitudinis , as observed in our study.…”

Optimization of Heavy Metals Biosorption via Artificial Neural Network: A Case Study of Cobalt (II) Sorption by Pseudomonas alcaliphila NEWG-2

“…The potentiality of industrial effluents containing heavy metal ions, such as copper, chromium, lead, and nickel, toward the environment had been reported to be a cause of the virulent impact on a variety of living organisms (i.e., plants, animals, and human beings) ( Alotaibi et al, 2021 ). These metals can accumulate in tissues of animals, and also in the human body ( Alfadaly et al, 2021 ), causing disruption of cell membranes, lipid peroxidation, inhibition of oxidative phosphorylation, protein denaturation, and alteration of nucleic acids structures ( Xie et al, 2016 ).…”