Molecular basis for resistance to silver cations in Salmonella
Amit Gupta, Kazuaki Matsui, Jeng-Fan Lo
& Simon Silver
Department of Microbiology & Immunology, University of Illinois at Chicago, M/C 790, Room 703, 835 South Wolcott Avenue, Chicago, Illinois 60612−7344, USA
Correspondence should be addressed to Amit Gupta agupta@uic.edu
Here we report the genetic and proposed molecular basis for silver resistance
in pathogenic microorganisms. The silver resistance determinant from a hospital
burn ward Salmonella plasmid contains nine open reading frames, arranged
in three measured and divergently transcribed RNAs. The resistance determinant
encodes a periplasmic silver−specific binding protein (SilE) plus apparently
two parallel efflux pumps: one, a P−type ATPase (SilP); the other, a
membrane potential−dependent three−polypeptide cation/proton antiporter
(SilCBA). The sil determinant is governed by a two−component
membrane sensor and transcriptional responder comprising silS and silR, which are co−transcribed. The availability of the sil
silver−resistance determinant will be the basis for mechanistic molecular
and biochemical studies as well as molecular epidemiology of silver resistance
in clinical settings in which silver is used as a biocide.
