ROLE OF EXOPOLYMER AND ACID-TOLERANCE IN THE GROWTH OF BACTERIA IN SOLUTIONS WITH HIGH COPPER ION CONCENTRATION

When copper-resistant Escherichia coli HB101 cells were transferred from regular to copper-amended, 1/3 strength Tryptic Soy Broth (TSB), there was an increase in the amount of exopolymer produced. The copper binding abilities of exopolymer for Pseudomonas aeruginosa 7, P. pseudomallei 13-1 (both copper-resistant) and from P. putida 3 (copper-sensitive), were also determined. If treated with phenol, about 50 to 75% of the copper binding ability of these exopolymers was removed. Although the amount of copper ion bound by the exopolymer isolated from P. putida 3 was about the same as from the resistant organisms, it did not grow in medium containing 0.5ppm copper ion. When free copper ion concentration in 1/3 strength TSB increased to 0.5ppm, the pH value of the broth dropped from 6.8 to 4.9. We believe this was what prevented the growth of the P. putida 3 in the solution containing the high concentration of copper ion.