Ramunas Stepanauskas,1,2,* Travis C. Glenn,1,3 Charles
H. Jagoe,1 R. Cary Tuckfield,4 Angela H. Lindell,1
Catherine J. King1 and J Vaun McArthur1
1University
of Georgia, Savannah River Ecology Laboratory, Aiken, SC, USA
2Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor,
ME, USA
3Department of Biological Sciences, University of South Carolina,
Columbia, SC, USA
4Savannah River National Laboratory, Aiken, SC,USA
Summary
Bacterial resistances to diverse metals and antibiotics are often genetically
linked, suggesting that exposure to toxic metals may select for strains
resistant to antibiotics and vice versa. To test the hypothesis that resistances
to metals and antibiotics are coselected for in environmental microbial
assemblages, we investigated the frequency of diverse resistances in freshwater
microcosms amended with Cd, Ni, ampicillin or tetracycline. We found that
all four toxicants significantly increased the frequency of bacterioplankton
resistance to multiple, chemically unrelated metals and antibiotics. An
ampicillin-resistant strain of the opportunistic human pathogen Ralstonia
mannitolilytica was enriched in microcosms amended with Cd. Frequencies
of antibiotic resistance were elevated in microcosms with metal concentrations
representative of industry and mining-impacted environments (0.01-1 mM).
Metal but not antibiotic amendments decreased microbial diversity, and
a weeklong exposure to high concentrations of ampicillin (0.01-10 mg l-1)
and tetracycline (0.03-30 mg l-1) decreased microbial abundance
only slightly, implying a large reservoir of antibiotic resistance in
the studied environment. Our results provide first experimental evidence
that the exposure of freshwater environments to individual metals and
antibiotics selects for multiresistant microorganisms, including opportunistic
human pathogens.
*Email
rstepanauskas@bigelow.org
Tel. (+1) 207 633 9681; Fax (+1) 207 633 9641
SREL
Reprint #2986
Stepanauskas, R., T. C. Glenn, C. H. Jagoe, R. C. Tuckfield, A. H. Lindell, C. J. King, and J V. McArthur. 2006. Coselection for microbial resistance to metals and antibiotics in freshwater microcosms. Environmental Microbiology 8 (9), 1510-1514.
