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Elucidating the genetic basis for Escherichia coli defense against silver toxicity using mutant arrays
Author(s) -
Xiu Zongming,
Liu Yuanyuan,
Mathieu Jacques,
Wang Jing,
Zhu Dongqiang,
Alvarez Pedro J.J.
Publication year - 2014
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2514
Subject(s) - escherichia coli , mutant , silver nanoparticle , oxidative stress , chemistry , extracellular , microbiology and biotechnology , gene , biology , transmission electron microscopy , biophysics , biochemistry , nanoparticle , materials science , nanotechnology
Bacterial adaptation and defense mechanisms against silver are poorly understood at the genetic level. A library of Escherichia coli gene‐deletion mutants was used to show that clones lacking sodB (coding for oxidative stress protection), lon (protein damage repair), or cusR (metal efflux pump) are quite sensitive to silver (with 7.3 ± 9.1%, 5.3 ± 1.8%, and 0.4 ± 0.1% of cells surviving, respectively, compared with 90.1 ± 5.4% survival for wild‐type E. coli , after 6‐h exposure to 8 mg/L AgNO 3 ), suggesting the importance of the coded functions as defense mechanisms. Mutants lacking pgaB or wcaD , which code for production of extracellular polymeric substances (EPS), also showed significant ( p < 0.05) sensitivity to silver exposure (23.4 ± 16.2% and 23.1 ± 32.6% survival, respectively). Transmission electron microscopy (TEM) with scanning TEM/energy‐dispersive X‐ray spectroscopy analysis showed accumulation of silver nanoparticles within EPS, suggesting that EPS serve as a protective barrier that also immobilizes dissolved silver as silver nanoparticles. Environ Toxicol Chem 2014;33:993–997 . © 2014 SETAC