Bacteria; An Efficient Bioremediator of Heavy Metals (original) (raw)
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The potential of naturally occurring bacteria for the bioremediation of toxic metals pollution
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An increase in industrialization and various kind of human activities added a huge amount of toxic heavy metals in the soil. As a result, toxic heavy metals in the environment may be adversely affects human being and aquatic ecosystem. Thus, it is very essential to understand mechanism of bioremediation through eco-friendly agent i.e. bacteria. Accumulation of high metal concentrations in soil above threshold limit causes lethal to bacterial communities in the environment. Few bacteria develop resistance mechanism to tolerate these toxic heavy metals and contain various methods to respond the metal stress. The present review emphasizes to understand the mechanism of bacterial resistance against toxic metals. Moreover, mechanism of bioaugmentation, biosorption, and bioaccumulation methods also described clearly.
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Heavy metals are persistent in nature and toxic to all life forms. Increase in industrialization, urbanization and unsafe agriculture practices is constantly adding heavy metals to the environment, and consequently causing heavy metal pollution of water and soil. Considering the negative impacts of heavy metals on the environment, several strategies have been devised to remediate them. However, most of these have their own limitations. Bioremediation of metals by microorganisms is efficient, cost-effective and environmentfriendly method of metal detoxification. Microbes can utilize metal contaminants as their energy source and transform them to less toxic forms. When exposed to metals for a considerable period of time, microorganisms interact with them and become tolerant by developing resistance mechanism against them. Metalmicrobe interactions can occur in several ways such as biosorption, bioleaching, biomineralization, bioaccumulation and biotransformation. Study of these interactions is important to understand resistance mechanisms against metals which include barriers, efflux system, sequestration and reduction of metals. These mechanisms are encoded by the resistance genes localized in chromosomes and plasmids. Understanding resistance mechanisms against metals in microorganisms becomes crucial for devising strategies for bioremediation of metals.
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Microorganisms have numerous biotechnological applications for bioremediation of metal-contaminated soil and water systems. In view of this, the present study was aimed to evaluate the abilities of microorganisms for tolerance and biosorption of heavy metals. In this study we have isolated 30 different bacterial strains from soil. Morphological and biochemical characterization was carried out. It was shown that Pseudomonas sp. was most common isolate among heavy metal resistant organisms that are capable of resisting 5 heavy metals (Ni, Pb, Cr, Cu and Cd) of concentration range 50-300µg/ml. Among 30 isolates, 4 of them showed high degree of resistance against all metals at concentration at 300µg/ml. Bacterial strains isolated in this study can be used in bioremediation and bio-mining.
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Heavy metal pollution generally occurs due to socio-economic, industrial, and anthropogenic activities, which may cause an environmentally hazardous and serious severe threat to the survival of the organisms (genotoxic, carcinogenic, and clastogenic effects on it). Many physical and chemical remediation approaches have been proposed to deal with this pollution, but these are very time-consuming and costly. While bioremediation stands out as an inexpensive and efficient approach, the use of bacteria is thought to be a potential and productive organism to prevent this pollution. This review has evaluated the bacterial potential to clean up heavy metals from the environment and elucidated the mechanisms responsible for bioremediation.
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Heavy metals accumulated the earth crust and causes extreme pollution. Accumulation of rich concentrations of heavy metals in environments can cause various human diseases which risks health and high ecological issues. Mercury, arsenic, lead, silver, cadmium, chromium, etc. are some heavy metals harmful to organisms at even very low concentration. Heavy metal pollution is increasing day by day due to industrialization, urbanization, mining, volcanic eruptions, weathering of rocks, etc. Different microbial strains have developed very efficient and unique mechanisms for tolerating heavy metals in polluted sites with eco-friendly techniques. Heavy metals are group of metals with density more than 5 g/cm3. Microorganisms are generally present in contaminated sites of heavy metals and they develop new strategies which are metabolism dependent or independent to tackle with the adverse effects of heavy metals. Bacteria, Algae, Fungi, Cyanobacteria uses in bioremediation technique and acts ...
Annals of advances in chemistry, 2018
Heavy metals and metalloids are dangerous because they have the tendency to bioaccumulate in biological organisms over a period of time. However, it is conceived that a number of phytochemical agents as well microorganism can act as heavy metal removing agent both from human beings and the environment surrounding. For instance, microbes are used for the removal of heavy metals from the water bodies including bacteria, fungi, algae and yeast. This review shows that bacteria can play an important role in understanding the uptake and potential removal behaviour of heavy metal ions. The bacteria are chosen based on their resistance to heavy metals (incl. their toxicities) and capacity of adsorbing them. Due to specifi c resistance transfer factors, cell impermeability is drastically inhibited by several ion (i.e. mercury, cadmium, cobalt, copper, arsenic) forms. Between these elements, free-ion cadmium and copper concentrations in the biological medium provide more accurate determination of metal concentrations that affect the bacteria, than with most of the other existing media. Metal toxicity is usually assessed by using appropriate metal ion chelators and adjusting pH factor. Bacteria and metals in the ecosystem can form synergistic or antagonistic relationships, supplying each other with nutrients or energy sources, or producing toxins to reduce growth and competition for limiting nutritional elements. Thus, this relation may present a more sustainable approach for the restoration of contaminated sources.
Mechanisms of Bacterial Resistance to Heavy Metals: A Mini Review
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Because of rising levels of heavy metal pollution in the environment, microbial resistance to heavy metals has become an increasing concern. Heavy metal resistance in bacteria is typically achieved through a combination of passive and active mechanisms, including heavy metal sequestration, efflux, or transformation within the microbial cell. During the efflux mechanism, a membrane protein's energy-dependent ion efflux from the cell is necessary for heavy metal removal. Understanding the physicochemical parameters of the environment, structure and diversity of microbial communities, nature and concentration of heavy metals is critical for developing effective strategies for the remediation of heavy metal-contaminated sites. Many microbes play a significant part on functioning ecosystem more especially in the biogeochemical cycling of heavy metals by removing the metals from the environment. As, Pb, Cd, and Hg are among heavy metals that are associated with the most common ecologi...
Role of Heavy Metal Resistant Bacteria for Bioremediation of Polluted Environment
THE JOURNAL OF MICROBIOLOGY AND MOLECULAR GENETICS
Bioremediation refers to the use of microorganisms to reduce or eliminate contaminants from water and soil. In the current research, different bacterial strains were screened for their chromate and arsenate reduction potential. For the removal of arsenic, eight arsenic resistant bacterial strains AsK03, AsK04, AsK06, AsK07, AsK08, AsK09, AsK15 and AsK18 and for chromium removal, eight chromium resistant bacterial strains CrK02, CrK08, CrK12, CrK14, CrK16, CrK19, CrK20 and CrK21 were isolated and selected, respectively, from several contaminated soil and water samples taken from tanneries located in Kasur. Resistance to chromium and arsenic was shown by all the strains on nutrient agar at preliminary concentration of 500 µg ml-1 . The maximum tolerable concentration (MTC) of these isolates was also studied. It was found that for arsenic resistance, two strains AsK04 and AsK09 had highest MTC of 100 mg ml-1 , AsK18 had 75 mg ml-1 , AsK03, AsK06 and AsK15 had 50 mg ml-1 and AsK07 and A...
Resistance of environmental bacteria to heavy metals
Bioresource Technology, 1998
Bacteria were isolated from different naturally polluted environments. Metal-resistant bacteria were selected and minimal inhibitory concentrations of heavy metals (MICs) for each isolate were determined. In addition, the mobility of the most important metallic cations (Cu, Zn, Cr, Cd, Co, Hg) was evaluated by comparing results obtained by two tests of toxicity in solid and liquid media. Results of the test of toxicity in solid media agreed with those in liquid, however, inhibitory concentrations in solid media were much higher than those in liquid. The range of metal concentrations tolerated in solid and liquid media yielded information on the capacity of adsorption and complexation of the metals. Mercury, and to a lesser degree copper, seemed to have a good capacity for adsorption and complexation and, consequently, had a limited diffusion in different naturally polluted environments. The presence of metals in the growth medium allowed us to maintain the tolerance of bacteria at a comparable level with that observed in naturally polluted environments. Cu and Cr were the best tolerated metals. Hg was the most toxic component for all bacteria, followed by Co and Cd. Pseudomonas aeruginosa (strain $6), with a relatively high MIC for metals and a large spectrum of antibiotic resistance appears to be a bacterial model for eco-toxicological studies.
Cytotoxicity and Bioremediation of Heavy Metals by Highly Resistant Marine Bacteria
Journal of Advances in Biology & Biotechnology, 2021
Environmental pollution of heavy metals is increasingly becoming a problem and has become of great concern due to the adverse effects it is causing around the world. These inorganic pollutants are being discarded in our waters, soils and into the atmosphere due to the rapidly growing agriculture and metal industries, improper waste disposal, fertilizers, and pesticides. Pollution in industrial areas is a serious environmental concern. Wastewater containing biotoxic substances of heavy metals in the ecosystem is one of the most important environmental and health challenges in our society. Hence, there is a growing need for the development of novel, efficient, eco-friendly, and cost-effective approach for the remediation of inorganic metals (Cr, Hg, Cd, and Pb) released into the environment and to safeguard the ecosystem. Mercury (Hg), Chromium (Cr), Cadmium (Cd), and lead (Pb) are known to cause damage to living organisms, including human beings. In this regard, recent advances in mi...