Possible role of E. coli chromosomal arsenic resistant operon in selenite tolerance

Abstract

Bioremediation is a method in which microorganisms are employed to clean up the polluted environment. In the present study we used a multimetal resistant bacterium Enterobacter sp. YSU, as our model of bioremediation. A 100 kb plasmid, pOR1, from Enterobacter sp. YSU conferred resistance to 40 mM selenite when it was transferred to Escherichia coli strain HB101 to create the new strain HB101(pOR1). Transposon mutagenesis of the pOR1 strain resulted a new strain selenite sensitive strain called G50 with the transposon inserted between 5' end of glutathione reductase and the 3' end of the arsenic resistance genes. The chromosomal arsenic resistance genes of E. coli confer a weak level of arsenic resistance and require plasmid encoded genes to provide stronger levels of resistance. A knock out was carried out on pOR1 using pRed ET kit and a new strain, pRed Ars, was generated and minimal inhibitory concentration experiments (MIC) and growth curves were carried out on pOR1, G50 and pRed Ars strains using sodium arsenite and sodium selenite. From the MIC and RT PCR experiments it was concluded that ars operon may not be responsible for selenite resistance.