Cadmium-Resistance Plasmid Affected Cd+2 Uptake More Than Cd+2 Adsorption in Klebsiella oxytoca
Khaled M. Khleifat; Khaled Nawayseh; Nawel R. Adjeroud; Ali M. Khlaifat; Isam H. Aljundi; Khaled A. Tarawneh
Abstract
A bacterial strain was isolated from Petra City Wastewater Treatment Plant. This isolate was identified as Klebsiella oxytoca based on 16S rDNA analysis. A single plasmid (> 23 kb) was detected in this strain and transformed into Esherichia coli JM83. The transformed E. coli cells exhibited elevated resistance to cadmium as compared to parental plasmid-free cells. The sodium dodecyl sulfate (SDS)-treated cells showed higher efficiency in plasmid curing than the ethidium bromide-treated cells. The ethidium bromide-cured cells grew only in a 10 μ g/ml Cd+ 2 minimal tolerable concentration, whereas the SDS-treated cells had no growth in any of the Cd concentrations tested (2, 5, 10, 20, 30, 40, and 50 ppm). Contrary to the Freundlich model, the Langmuir model gave a good fit to the Cd biosorption data by K. oxytoca cells. Plasmid curing caused 80%, 82%, and 70% inhibition in the Cd biosorption, adsorption, and uptake, respectively. Furthermore, the absence of lysine decarboxylase (LDC) activity in the cured strain strongly implies that the structural gene-encoding LDC in this bacterium is plasmid encoded. After curing of the plasmid, 100% of the antibiotic-resistant loci were observed as chromosomal encoded. All of the results shown above indicated that the Cd resistance is plasmid mediated.
DOI: 10.1080/10889860903080739
Published in: Bioremediation Journal, Volume 13, Issue 4 October 2009 , pages 159 - 170
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