Abstract
Media used to determine the MICs of heavy metals for bacteria are unreliable because organic components in the media bind or chelate most of the metal being studied. To define specific metal activity in media and to maintain metal activity at a constant level, HEPES-MES [N-2-hydroxyethylpiperazine-N′ -2-ethanesulfonic acid−2-(N-morpholine)ethanesulfonic acid] salts medium with arabinose medium was modified, and the modified medium was used to examine the MIC of cadmium for Rhizobium fredii USDA 201. Arabinose-HEPES-MES was modified by addition of the chelator nitrilotriacetate to buffer the supply of free Cd2+ ion to maintain a constant Cd activity and by the use of only MES to buffer pH (buffered arabinose-MES medium [BAM]). Ca and Mg were supplied at the normal levels for soil solutions, and other trace elements were supplied at the levels required for normal growth of plants. The concentration of free Cd2+ ion was calculated by using the computer program GEOCHEM-PC with a corrected data base. The Cd MIC in BAM was 14.0 μM, while that in a tryptone-yeast extract medium was 107 μM. The results indicate that substantial free Cd2+ is removed from solution in most standard media, resulting in falsely high MICs. The new BAM medium allows for the precise determination of MICs, thus avoiding the uncertainties associated with other media.
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Selected References
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- Allen D. A., Austin B., Colwell R. R. Antibiotic resistance patterns of metal-tolerant bacteria isolated from an estuary. Antimicrob Agents Chemother. 1977 Oct;12(4):545–547. doi: 10.1128/aac.12.4.545. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Babich H., Stotzky G. Reductions in the toxicity of cadmium to microorganisms by clay minerals. Appl Environ Microbiol. 1977 Mar;33(3):696–705. doi: 10.1128/aem.33.3.696-705.1977. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Beringer J. E. R factor transfer in Rhizobium leguminosarum. J Gen Microbiol. 1974 Sep;84(1):188–198. doi: 10.1099/00221287-84-1-188. [DOI] [PubMed] [Google Scholar]
- Cole M. A., Elkan G. H. Transmissible resistance to penicillin G, neomycin, and chloramphenicol in Rhizobium japonicum. Antimicrob Agents Chemother. 1973 Sep;4(3):248–253. doi: 10.1128/aac.4.3.248. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Higham D. P., Sadler P. J., Scawen M. D. Cadmium-Resistant Pseudomonas putida Synthesizes Novel Cadmium Proteins. Science. 1984 Sep 7;225(4666):1043–1046. doi: 10.1126/science.225.4666.1043. [DOI] [PubMed] [Google Scholar]
- Kinkle B. K., Angle J. S., Keyser H. H. Long-Term Effects of Metal-Rich Sewage Sludge Application on Soil Populations of Bradyrhizobium japonicum. Appl Environ Microbiol. 1987 Feb;53(2):315–319. doi: 10.1128/aem.53.2.315-319.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lighthart B. Enrichment of cadmium-mediated antibiotic-resistant bacteria in a Douglas-fir (Pseudotsuga menziesii) litter microcosm. Appl Environ Microbiol. 1979 May;37(5):859–861. doi: 10.1128/aem.37.5.859-861.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mitra R. S., Gray R. H., Chin B., Bernstein I. A. Molecular mechanisms of accommodation in Escherichia coli to toxic levels of Cd2+. J Bacteriol. 1975 Mar;121(3):1180–1188. doi: 10.1128/jb.121.3.1180-1188.1975. [DOI] [PMC free article] [PubMed] [Google Scholar]