Silver is a heavy metal with relatively high toxicity to prokaryotes, and silver salts are used as antiseptics to prevent
Neisseria infections in the eyes of newborn infants and to control infections in burns (Russell and Hugo, 1994). Research on microbial
with silver has focused on toxicity, resistance, and accumulation (Slawson et al, 1992).
Silver resistance has been described in Gram-positive and Gram-negative bacteria (Nies, 1999)
representing clinical (McHugh et al,
1975) and environmental (Deshpande and Chopade, 1994; Haefeli et al, 1984) isolates.
The genes mediating plasmid-based silver resistance in Salmonella have been identified and were
found to encode a periplasmic silver-binding protein and two parallel efflux pumps--a P-type ATPase and a cation/proton antiporter (Gupta et al, 1999). Silver resistance in Eschericia coli appears to be controlled by a chromosomally encoded efflux pump (Li et al, 1997)
that may involve the protein encoded by gene ybdE (Franke et al, 2001). In
Enterococcus hirae, a copper-exporting ATPase may also function to export silver (Solioz and Odermatt,
Some silver resistant bacteria accumulate silver instead
of exporting silver. When grown in the presence of silver ions, Pseudomonas stutzerii deposited silver in regularly shaped
crystalline particles in the periplasmic space (Klaus et al, 1999). Research has been conducted on the ability of bacteria to recover silver ions from photographic (Shakibaie et al, 1999)
and Paknikar, 2000) industry wastewaters. Fungal chitins can also bind silver ions with high affinity, and biosorption of silver by
living and dead fungal biomass has been
investigated (Fourest et al,
For more information:
Medline for silver metabolism AND bacteria
Gupta A, Phung LT, Taylor DE, and Silver, S. Diversity of silver resistance genes in IncH
incompatibility group plasmids. Microbiology. 2001 Dec;147(Pt12):3393-402.
Mullen MC, Wolf DC, Ferris FG, Beveridge TJ, Flemming CA, Bailey GW. Bacterial sorption of heavy metals. Appl Environ Microbiol. 1989 Dec;55(12):3143-9.