Bioaccumulation of silver by a multispecies community of bacteria

Charley, Robert C.; Bull, Alan T.

doi:10.1007/bf00406656

Cited by 86 publications

(20 citation statements)

References 10 publications

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“…The microbicidal action of silver compounds at low concentrations reflects the ability of bacteria, trypanosomes, and yeasts to take up and concentrate silver from very dilute solutions. 13 It was shown that bacteria killed by silver may contain 10 5 -10 7 Ag þ per cell, the same order of magnitude as the estimated number of enzyme-protein molecules per cell. This showed that through chemical chelation, the enzyme-protein molecules in bacteria cell can absorb silver ions from the contacting solution.…”

Section: Resultsmentioning

confidence: 98%

“…When low concentrations of silver ions accumulate inside cells, they can bind to negatively charged components in proteins and nucleic acids, thereby effecting structural changes in bacterial cell walls, membranes, and nucleic acids that affect viability. [13][14][15] Interestingly, although silver is a highly effective antimicrobial agent, it has a limited toxicity to mammalian cells. 16 It was found that the use of silver containing wound dressings can increase the rate of epithelialization by 28%, indicating a beneficial effect of silver ions to skin regeneration, in addition to its antimicrobial activity.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and characterization of silver containing chitosan fibers

Qin

Zhu

Chen

et al. 2007

J of Applied Polymer Sci

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Silver containing chitosan fibers were prepared by blending fine particles of a silver sodium hydrogen zirconium phosphate compound into the spinning solution. It was possible to distribute the silver containing particles in the chitosan fiber because of the high viscosity of the spinning solution and the small diameter of the particles. Because the silver ions are imbedded inside the sodium hydrogen zirconium phosphate complex, the chitosan fibers remain white in color without being oxidized by the silver ions. The release of silver ions from the silver containing chitosan fibers were studied by placing the fibers in contact with distilled water, solution A, and aqueous protein solutions. Results showed that the release of silver ions was low in water, while in solution A and protein solutions, the silver ions are activated through ion exchange and chelation. The silver ions can significantly enhance the antimicrobial properties of the chitosan fibers. Experimental results showed that when placed in contact with the silver containing chitosan fibers, the reduction in bacteria count can be more than 98%.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of silver containing chitosan fibers

Qin

Zhu

Chen

et al. 2007

J of Applied Polymer Sci

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“…Binding of silver by bacteria is also of interest to those hoping to recover metals from industrial effluents and waste materials (47,48,49) or by leaching from minerals (50) (Table I). Such workers have also looked at the localization of silver, but usually treat the bacteria with much more concentrated solutions than the AgSu work referred to above (mM rather than M).…”

Section: Water Sterilizationmentioning

confidence: 99%

Antibacterial Silver

1994

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The antibacterial activity of silver has long been known and has found a variety of applications because its toxicity to human cells is considerably lower than to bacteria. The most widely documented uses are prophylactic treatment of burns and water disinfection. However, the mechanisms by which silver kills cells are not known. Information on resistance mechanisms is apparently contradictory and even the chemistry of Ag + in such systems is poorly understood. Silver binds to many cellular components, with membrane components probably being more important than nucleic acids. It is difficult to know whether strong binding reflects toxicity or detoxification: some sensitive bacterial strains have been reported as accumulating more silver than the corresponding resistant strain, in others the reverse apparently occurs. In several cases resistance has been shown to be plasmid mediated. The plasmids are reported as difficult to transfer, and can also be difficult to maintain, as we too have found. Attempts to find biochemical differences between resistant and sensitive strains have met with limited success: differences are subtle, such as increased cell surface hydrophobicity in a resistant Escherichia coli. Some of the problems are due to defining conditions in which resistance can be observed. Silver(I) has been shown to bind to components of cell culture media, and the presence of chloride is necessary to demonstrate resistance. The form of silver used must also be considered. This is usually water soluble AgNO 3 , which readily precipitates as AgCl. The clinically preferred compound is the highly insoluble silver sulfadiazine, which does not cause hypochloraemia in burns. It has been suggested that resistant bacteria are those unable to bind Ag + more tightly than does chloride. It may be that certain forms of insoluble silver are taken up by cells, as has been found for nickel. Under our experimental conditions, silver complexed by certain ligands is more cytotoxic than AgNO 3 , yet with related ligands is considerably less toxic. There is evidently a subtle interplay of solubility and stability which should reward further investigation.

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“…It has been suggested that the mechanism of Ag+ resistance may be similar to mercuric reductase activity found in some mercury-resistant bacteria (Charley and Bull, 1979;Belly and Kydd, 1982). Ag +-dependent oxidation of NADPH was measured spectrophotometrically at 340 nm in MES buffer with the protocol described by Izaki (1981).…”

Section: Discussionmentioning

confidence: 93%

“…Silver-resistant bacteria have been isolated and studied (Charley and Bull, 1979), but were not examined for the possibility that resistance was plasmid-encoded. Belly and Kydd (1 982) isolated silver-resistant bacteria, yeast and fungi ; resistant bacteria were able to tolerate 300 ppm of AgN03 whereas sensitive strains failed to grow in the presence of 1-10 ppm.…”

Section: Introductionmentioning

confidence: 99%

Silver resistance in Escherichia coli R1

Starodub

Trevors

1989

Journal of Medical Microbiology

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Summary. Escherichia coli strain Rl, originally isolated from a patient whose burns were treated with silver sulphadiazine, contained two large plasmids of 83 kb (pJT1) and 77 kb (pJT2), and was resistant to 1 mM AgN03. A silver-sensitive derivative, E. coli S1, cured of the 83-kb plasmid pJT1, was obtained by growth at 46°C. Studies with an Ag+-specific ion electrode showed no significant differences in Ag' binding by washed resting cell suspensions of strains R l and S1, with and without glucose. However, transmission electronmicroscopy and energy dispersive X-ray analysis of whole cell mounts from actively growing cultures showed that the Ag +-resistant strain did not accumulate Ag', whereas the sensitive strain contained dense silver particles. Both strains produced H2S, detected by blackening of lead acetate paper above inoculated broth, and reducing substances (possibly H2S) were detected only around E. coli R1 colonies when methylene blue was used as a indicator in LB agar, which may be a less sensitive assay. The mechanism of silver resistance is not known, but actively growing cells of E. coli R l did not accumulate silver.

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Bioaccumulation of silver by a multispecies community of bacteria

Cited by 86 publications

References 10 publications

Preparation and characterization of silver containing chitosan fibers

Preparation and characterization of silver containing chitosan fibers

Antibacterial Silver

Silver resistance in Escherichia coli R1

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