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Molecular Approaches for Removal of Toxic Metal by Genetically Modified Microbes
Published in Maulin P. Shah, Wastewater Treatment, 2022
Joorie Bhattacharya, Rahul Nitnavare, Sougata Ghosh
The reduction of oxidative stress post-bioaccumulation of heavy metals was explored by studying metal-binding proteins (MBPs). Enzymes and other peptides that bind to heavy metals also can be used to improve the storage in microorganisms (Diep et al., 2018; Verma and Kuila, 2019). Considering the risk assessment associated with GEMs, there are a few factors that need to be kept in mind throughout their practical application. The stability of the microbe must be ensured prior to field applications as the activity of the GEM is concomitant to the plasmid introduced into it. Additionally, the GEM would only be profitable if it is able to express the desired traits in the native environments as well as is to survive accordingly. The microorganism is greatly affected by the abundance to competing microbes, growth rate, spatial distribution, and the environmental conditions at the time of expression. Any deviation from the laboratory environment would also affect the bioremediation efficacy.
Mechanism of Heavy Metal Hyperaccumulation in Plants
Published in Amitava Rakshit, Manoj Parihar, Binoy Sarkar, Harikesh B. Singh, Leonardo Fernandes Fraceto, Bioremediation Science From Theory to Practice, 2021
Apart from sequestration, detoxification of heavy metals is another strategy adopted by hyperaccumulators to avoid toxicity. Heavy metal toxicity is avoided by binding them to certain metal binding proteins or ligands. The association of heavy metals with ligands prevents the persistence of heavy metal as free ions in the cytoplasm (Rascio and Navari-Izzo 2011). The best known ligands for this purpose are thiols including glutathione, phytochellatins and metallothioneins and non thiols such as histidine and nicotinamide. Non thiols are more significant in hyperaccumulators rather than high molecular mass ligands like phytochelatins because of the excessive amount of sulphur and high metabolic cost that this kind of chelation requires (Schat et al. 2002, Rabb et al. 2004).
Microbial Metalloproteins-Based Responses in the Development of Biosensors for the Monitoring of Metal Pollutants in the Environment
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Metalloproteins have a particular structure with sequential arrangement of amino acids promoting higher selectivity to specific metals compared to other metal-binding proteins. This attribute makes them very attractive as bioreceptors for biosensors (Fig. 1). Bontidean et al. (1998) developed sensors based on proteins (GST-SmtA and MerR) with distinct binding sites for heavy metal ions by overexpressing the above proteins in E. coli and immobilizing the pure proteins at surface of gold electrode. Following exposure to zinc, cadmium, copper, and mercury ions, the selectivity and sensitivity of the two protein-based biosensors were measured; the MerR-based electrodes showed an accentuated selectivity for mercury only, while the GST-SmtA electrodes were able to sense all the four heavy metals. Corbisier et al. (1999)overexpressed the fusion protein GST-SmtA, containing glutathione-S-transferase linked to the Synechococcal metallothionein protein in E. coli from an expression vector pGEX3X containing SmtA, the fusion protein was then immobilized on gold surface to prepare the biosensor.
Investigation of metallothionein level, reduced GSH level, MDA level, and metal content in two different tissues of freshwater mussels from Atatürk Dam Lake coast, Turkey
Published in Chemistry and Ecology, 2019
Organisms in aquatic ecosystems have developed various protective mechanisms against environmental conditions and pollution [17]. Long-term exposure to environmental pollutants may cause a variety of damage to aquatic organisms [18]. The intracellular level of reactive oxygen species (ROS) in aquatic organisms can be increased in the presence of excess metal. To protect against ROS damage, organisms have developed complex antioxidants and detoxifying mechanisms that can inhibit ROS production [15,19,20]. Several biochemical markers are used to evaluate the oxidative stress in mussels that are exposed to metals [21]. Glutathione (GSH) is a tripeptide composed of glutamic acid, cysteine, and glycine amino acids. It is an intracellular antioxidant that plays an important role in xenobiotic damage, cellular defense, detoxification of drugs, and controling the release of ROS [22,23]. Malondialdehyde (MDA) is a product of lipid hydroperoxidation and is considered an important biochemical marker for chemical damage in mussels exposed to aquatic pollutants such as metals [24–26]. Metal-binding proteins such as metallothioneins (MT) are widely used as an important biochemical marker for both oxidative stress and metal toxicity. Because of their high cysteine content, they play an active role in the scavenging of free radicals [21,27]. It is also well known that they have important roles in metal homeostasis and metal detoxification because of their high affinity to metal ions [21].
A Review on Heavy Metals Contamination in Soil: Effects, Sources, and Remediation Techniques
Published in Soil and Sediment Contamination: An International Journal, 2019
Changfeng Li, Kehai Zhou, Wenqiang Qin, Changjiu Tian, Miao Qi, Xiaoming Yan, Wenbing Han
The microorganisms most commonly used for the removal of heavy metals in contaminated soils are bacterial and fungi, although yeast and algae are also frequently applied (Coelho et al., 2015). Examples of microorganisms studies and strategically used bioremediation treatments for heavy metals include the following: Sporosarcina ginsengisoli (Achal et al., 2012), Pseudomonas putida (Balamurugan et al., 2014), and Bacillus subtilis (Imam et al., 2016). Bioremediation by microorganisms will be successful if a consortium of bacterial strains is utilized rather than a single strain culture. Kang et al. (2016) investigated the synergistic effect of bacterial mixtures (Viridibacillus arenosi B-21, Sporosarcina soli B-22, Enterobacter cloacae KJ-46, and E. cloacae KJ-47) on the bioremediation of a mixture of Cd, Cu, and Pb from contaminated soils. They observed that the bacterial mixtures demonstrated greater resistance and efficiency for the remediation of heavy metals compared with single-strain cultures. The mechanisms used in remediation of heavy metals from contaminated soils include microorganisms through the processes of precipitation, biosorption via sequestration by intracellular metal binding proteins, and conversion of metals to innocuous forms by enzymes (Ojuederie and Babalola, 2017).
Bioremediation of heavy metal polluted soil using plant growth promoting bacteria: an assessment of response
Published in Bioremediation Journal, 2022
Ifeoma Anthonia Okpara-Elom, Charles Chike Onochie, Michael Okpara Elom, Emmanuel Ezaka, Ogbonnaya Elom
The removal of heavy metals by microbial cells with high tolerance to heavy metals from contaminated environments such as soils can be a combination of biosorption, bioprecipitation, metabolic uptake of metals and bioaccumulation (Soares and Soares 2013). Jan et al. (2014) highlighted four (4) important mechanisms of microbial bioremediation to be through: (i) sequestration of toxic metals by cell wall components or by intracellular metal binding proteins and peptides such as metallothioneins (MT) and phytochelatins, along with compounds such as siderophores (ii) changing of biochemical pathways in order to block metal uptake (iii) enzymatic conversion of metals to harmless forms and (iv) reduction of intracellular concentration of metals by the use of precise efflux systems.