Removal of copper ion by Pseudomonas spp.

Copper-resistant Pseudomonas sp. 41Y, Pseudomonas pseudomallei 13-1 and Pseudomonas aeruginosa 7 were used in the present study. When the latter two organisms were added to copper-containing 1/3 strength Tryptic Soy Broth, more than 99.5% of the copper ion was removed from the medium within 24 h. If copper solution was added to hog waste slurry, a reduction in the copper ion concentration could be detected only when the added bacteria started to grow in it, whereas in a mineral medium supplemented with glycerol-2-phosphate, both bacteria could remove about 50% of the copper ion from the medium within 24 h. When cell suspension of Pseudomonas sp. 41Y was autoclaved, no copper ion removal was observed. Different incubation temperatures, including 30 degrees C, 37 degrees C and 45 degrees C, had no effect on the percent of copper ion removed by both Pseudomonas sp. 41Y and P. pseudomallei 13-1. On the other hand, if the pH value of the solution was lowered from 8.2 to 6.0, there was a drastic decrease in copper removal. A similar reduction of copper ion removal ability was also observed with the addition of lead ion. When cells of Pseudomonas sp. 41Y were embedded in sodium alginate, there was a decrease in its ability to remove copper ion as compared to the free-living cells.