Sorption and Transformation of Toxic Metals by Microorganisms

Han, Xu; Gu, Ji‐Dong

doi:10.1002/9780470495117.ch7

Cited by 22 publications

(21 citation statements)

References 95 publications

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“…The individual subunit masses are 100 kDa (␣), 55 kDa (␤), and 36 kDa (␥). It contains molybdenum, heme, and nonheme iron in its prosthetic groups and displays activity on chlorate and bromate but none on nitrate (39,62). It is noteworthy that the reductase of E. cloacae SLD1a-1 is similar to periplasmic Ser from T. selenatis.…”

Section: ϫmentioning

confidence: 87%

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Microbial Transformations of Selenium Species of Relevance to Bioremediation

Eswayah

Smith

Gardiner

2016

Appl Environ Microbiol

181

102

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b Selenium species, particularly the oxyanions selenite (SeO 3 2؊ ) and selenate (SeO 4 2؊ ), are significant pollutants in the environment that leach from rocks and are released by anthropogenic activities. Selenium is also an essential micronutrient for organisms across the tree of life, including microorganisms and human beings, particularly because of its presence in the 21st genetically encoded amino acid, selenocysteine. Environmental microorganisms are known to be capable of a range of transformations of selenium species, including reduction, methylation, oxidation, and demethylation. Assimilatory reduction of selenium species is necessary for the synthesis of selenoproteins. Dissimilatory reduction of selenate is known to support the anaerobic respiration of a number of microorganisms, and the dissimilatory reduction of soluble selenate and selenite to nanoparticulate elemental selenium greatly reduces the toxicity and bioavailability of selenium and has a major role in bioremediation and potentially in the production of selenium nanospheres for technological applications. Also, microbial methylation after reduction of Se oxyanions is another potentially effective detoxification process if limitations with low reaction rates and capture of the volatile methylated selenium species can be overcome. This review discusses microbial transformations of different forms of Se in an environmental context, with special emphasis on bioremediation of Se pollution. Since the discovery in 1954 by Pinsent that the oxidation of formate by cell suspensions of Escherichia coli requires growth medium containing molybdate and selenite, there has been a growing interest in the biochemical role of selenium in microorganisms (1). Se is an essential component of selenoamino acids, such as selenomethionine and selenocysteine (the 21st proteinogenic amino acid), that occur in certain types of prokaryotic enzymes. Indeed, the requirement for selenite in E. coli growing on formate is linked to the fact that formate dehydrogenase contains selenocysteine. Other prokaryotic enzymes that contain selenocysteine include glycine reductase in several clostridia, formate dehydrogenases in diverse prokaryotes, including Salmonella, Clostridium, and Methanococcus, as well as hydrogenases in Methanococcus and other anaerobes. In addition, other bacterial Se-dependent enzymes, in which the selenium is part of the active site molybdenum-containing cofactor, include nicotinic acid dehydrogenase and xanthine dehydrogenase, which is present in certain clostridial species (2-4).Reactions that are involved in the cycling of Se in soil, including those influenced by microbes, are diagrammatically summarized in Fig. 1 2Ϫ and was spatially separated from sulfate reduction in the environment despite the presence of substantial concentrations of sulfate where it occurred. Thus, it can be concluded that Se and S have different reductive biogeochemical cycles and appear to involve distinct populations of microorganisms.With respect to the remediation of sel...

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Section: ϫmentioning

confidence: 87%

“…Microorganisms that reduce the Se oxyanions SeO 3 2Ϫ and SeO 4 2Ϫ are not confined to any particular group of prokaryotes and are widely distributed throughout the bacterial and archaeal domains (37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49) Table 1.…”

Section: ϫmentioning

confidence: 99%

Microbial Transformations of Selenium Species of Relevance to Bioremediation

Eswayah

Smith

Gardiner

2016

Appl Environ Microbiol

181

102

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“…Microbes releasing chelating agents and acids altering physicochemical properties such as redox potential (Eh) of surroundings (Abou-Shanab et al 2003) bring substantial changes by increasing the bioavailability of metal ions (Abou-Shanab et al 2006). In addition, physicochemical reaction such as biosorption is the first step in the interaction between microbial cell and metal ions (Han and Gu 2010) followed by the physical adsorption, ion exchange and complexation (Fig. 1).…”

Section: Microbial Remediation Of Inorganic Contaminantsmentioning

confidence: 99%

“…1). Biochemical reactions during microbial transformation of metal ions involve the action of specific enzymes for oxidation, reduction, methylation, dealkylation and precipitation (Han and Gu 2010). Microbes have diversified conditions for their growth with ability to adapt to the changing environmental conditions, e.g., Naraian et al (2012) reported that the multiple-drug-resistant strain of Pseudomonas aeruginosa T-3 isolated from tannery effluent had plasmid-encoded chromate ion resistance, exhibiting the adaptability feature of microbes.…”

Section: Microbial Remediation Of Inorganic Contaminantsmentioning

confidence: 99%

“…pH values affect the solubility of metal ions, which increases with the decrease in pH of medium, thereby affecting adsorption by microbial cells (Blázquez et al 2008). In addition, lower pH values are required for metal ions to get attached on the microbial cell surface (Rajendran et al 2002;Han and Gu 2010), whereas alkaline medium favors precipitation of metal ions. Organic acid-producing microorganisms Pseudomonas sp.…”

Section: Physicochemical Factors Affecting Bioremediationmentioning

confidence: 99%

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Advances in microbial bioremediation and the factors influencing the process

Srivastava

Naraian

Kalra³

et al. 2013

Int. J. Environ. Sci. Technol.

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Irrational and rapid global human societal development has culminated to a condition of environmental deterioration. Accidental leakage and deliberate use of organic and inorganic chemicals have contaminated the environment up to the level of ecosystem. Advancements have been made in the field of research on bioremediation of the hazardous contaminants especially in last three decades. Microbial bioremediation has been the most understood biotechnological process of environmental restoration. Bacteria and fungi because of their inherent ability to adapt and grow in extreme environments have been employed for either removal or degradation of the chemical contaminants. Researchers all over the world are getting breakthroughs in finding new bacterial strains having plasmid linked degradation/ reduction ability. Molecular biology and genetic engineering helped in crafting the microbes for the desired results on environment. Despite having favorable conditions, microbial remediation largely depends on environmental factors and on the basic biological characters of microbes, especially bacteria being Grampositive or Gram-negative. Metagenomic studies revealed the importance of microbial ecology as microbes work well in community, i.e., consortia. This review along with several other studies suggests the need of precision during microbial community identification, substrate specificity and the designing of microbes.

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