Effect of heavy metals (Cu, Pb, and Ni) on the compositions of EPS in biofilms

Jang, Am; Kim, Sang-Myeong; Lee, S. G.; Kim, I. S.

doi:10.2166/wst.2001.0336

Cited by 76 publications

(32 citation statements)

References 8 publications

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“…Marine biofilms increase EPS production in response to several heavy metals, including copper (Fang et al, 2002), while EPS content of river biofilms substantially declines on exposure to Ni(II) (Lawrence et al, 2004). The carbohydrate/protein ratio is frequently altered by heavy metals, but the changes observed vary widely in different studies (Jang et al, 2001;Lawrence et al, 2004). Modifications in EPS composition of biofilms are attributed to the selective pressure of the heavy metals on the community, which favours bacterial populations producing an EPS having the characteristics that confer resistance to a particular metal ion (Lawrence et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

et al. 2007

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The structure, biological activity and microbial biodiversity of a biofilm used for the removal of copper from groundwater were studied and compared with those of a biofilm grown under copper-free conditions. A laboratory-scale submerged fixed biofilter was fed with groundwater (2.3 l h "1 ) artificially polluted with Cu(II) (15 mg l "1 ) and amended with sucrose (150 mg l "1 ) as carbon source. Between 73 and 90 % of the Cu(II) was removed from water during long-term operation (over 200 days). The biofilm was a complex ecosystem, consisting of eukaryotic and prokaryotic micro-organisms. Scanning electron microscopy revealed marked structural changes in the biofilm induced by Cu(II), compared to the biofilm grown in absence of the heavy metal. Analysis of cell-bound extracellular polymeric substances (EPS) demonstrated a significant modification of the composition of cell envelopes in response to Cu(II). Transmission electron microscopy and energy-dispersive X-ray microanalysis (EDX) showed that copper bioaccumulated in the EPS matrix by becoming bound to phosphates and/or silicates, whereas copper accumulated only intracytoplasmically in cells of eukaryotic microbes. Cu(II) also decreased sucrose consumption, ATP content and alkaline phosphatase activity of the biofilm. A detailed study of the bacterial community composition was conducted by 16S rRNA-based temperature gradient gel electrophoresis (TGGE) profiling, which showed spatial and temporal stability of the species diversity of copper-exposed biofilms during biofilter operation. PCR reamplification and sequencing of 14 TGGE bands showed the prevalence of alphaproteobacteria, with most sequences (78 %) affiliated to the Sphingomonadaceae. The major cultivable colony type in plate counts of the copper-exposed biofilm was also identified as that of Sphingomonas sp. These data confirm a major role of these organisms in the composition of the Cu(II)-removing community. INTRODUCTIONCopper is an essential trace element for all species studied to date, including humans (Fraga, 2005). However, a large excess intake of Cu(II) in drinking water can cause nausea, gastric irritation and vomiting, while long-term copper intoxication generates liver disease and severe neurological defects in humans (Hotz et al., 2003;Uriu-Adams & Keen, 2005). Chronic ingestion of drinking water with high Cu(II) concentrations (over 3 mg l 21 ) is thus a potential health risk, especially for susceptible populations like children ( Abbreviations: DGGE, denaturing gradient gel electrophoresis; EDX, energy-dispersive X-ray microanalysis; EPS, extracellular polymeric substances; LOI, loss on ignition; SEM, scanning electron microscopy; TEM, transmission electron microscopy; TGGE, temperature gradient gel electrophoresis; UPGMA, unweighted pair grouping with arithmetic averages. input in freshwaters is generated from a number of anthropogenic activities (Cameron, 1992), where these ions sequentially accumulate in sediments, bacteria, tubicid worms and fish, followed by uptake by humans thro...

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Section: Discussionmentioning

confidence: 99%

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

et al. 2007

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“…The EPS encasing a biofi lm protect cells from heavy metal stress by binding the metal ions or by retarding their diffusion within the biofi lm. Metals (Fe, Au, La, Cu) bound to biofi lm of Pseudomonas aeruginosa PAO1 signifi cantly exceeded those bound by planktonically grown cells [77,79].…”

Section: Biofi Lm Eps and Metal Bindingmentioning

confidence: 96%

“…In addition, carbohydrate : protein (C/P) ratio also plays a signifi cant role in monitoring the state of biofi lm process to remove heavy metals in the wastewater. In batch experiments, binding of Cu(II), Pb(II) and Ni(II) occurred with lowering of C/P ratio of EPS when exposed to Cu and Pb ions [77]. Using a rotating-disk biofi lm reactor it was demonstrated that biofi lms were more resistant to Cu, Pb and Zn than the stationary-phase or logarithmically growing planktonic cells [78].…”

Section: Biofi Lm Eps and Metal Bindingmentioning

confidence: 99%

Microbial extracellular polymeric substances: central elements in heavy metal bioremediation

2008

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Extracellular polymeric substances (EPS) of microbial origin are a complex mixture of biopolymers comprising polysaccharides, proteins, nucleic acids, uronic acids, humic substances, lipids, etc. Bacterial secretions, shedding of cell surface materials, cell lysates and adsorption of organic constituents from the environment result in EPS formation in a wide variety of free-living bacteria as well as microbial aggregates like biofi lms, biofl ocs and biogranules. Irrespective of origin, EPS may be loosely attached to the cell surface or bacteria may be embedded in EPS. Compositional variation exists amongst EPS extracted from pure bacterial cultures and heterogeneous microbial communities which are regulated by the organic and inorganic constituents of the microenvironment. Functionally, EPS aid in cell-to-cell aggregation, adhesion to substratum, formation of fl ocs, protection from dessication and resistance to harmful exogenous materials. In addition, exopolymers serve as biosorbing agents by accumulating nutrients from the surrounding environment and also play a crucial role in biosorption of heavy metals. Being polyanionic in nature, EPS forms complexes with metal cations resulting in metal immobilization within the exopolymeric matrix. These complexes generally result from electrostatic interactions between the metal ligands and negatively charged components of biopolymers. Moreover, enzymatic activities in EPS also assist detoxifi cation of heavy metals by transformation and subsequent precipitation in the polymeric mass. Although the core mechanism for metal binding and / or transformation using microbial exopolymer remains identical, the existence and complexity of EPS from pure bacterial cultures, biofi lms, biogranules and activated sludge systems differ signifi cantly, which in turn affects the EPS -metal interactions. This paper presents the features of EPS from various sources with a view to establish their role as central elements in bioremediation of heavy metals.

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“…It can be related to various defense mechanisms either specific (for instance metal efflux or 348 decrease of metal uptake by modification of channel or carrier proteins used by the metal ions to 349 enter the cells (Harrison et al, 2007) or non-specific, for instance production of metal-binding 350 EPS (Mason and Jenkins, 1995;Jang et al, 2001) to a metal. The fact that exposure to Pb 351 induced tolerance to both Pb and Zn but not to Cu suggests that, in this case, the exposed 352 community probably developed defense mechanisms that are specific to Pb and Zn.…”

Section: Pb Exposure Concentrations (Left Graphs) 287mentioning

confidence: 99%

Pollution-induced community tolerance of freshwater biofilms: measuring heterotrophic tolerance to Pb using an enzymatic toxicity test

Fechner¹,

Dufour²,

Gourlay-Francé³

2012

Ecotoxicology

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Effect of heavy metals (Cu, Pb, and Ni) on the compositions of EPS in biofilms

Cited by 76 publications

References 8 publications

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

Microbial extracellular polymeric substances: central elements in heavy metal bioremediation

Pollution-induced community tolerance of freshwater biofilms: measuring heterotrophic tolerance to Pb using an enzymatic toxicity test

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