Copper bioremoval by novel bacterial isolates and their identification by 16S rRNA gene sequence analysis

Copper-tolerant bacteria were isolated from soil samples taken from a region where metal industries are located. After selecting 2 isolates with relatively higher bioremoval efficiency, the effects of increasing copper concentration, pH, and temperature on the bioremoval efficiency of the growing isolates were determined. Strain N1c and strain N5a showed maximal bioremoval efficiency of 82% and 75%, respectively, in 20 mg/L copper-containing medium at pH 6.8 and 30 °C. Although the isolates did not grow well at pH 5, a low amount of copper was removed at pH 5. Slow growth of N5a at pH 5 allowed for 26% copper removal at hour 80 of incubation. Optimal copper bioremoval of the cells occurred at pH 6.8 and 30 °C. When grown at 37 °C under aerated conditions, N1c showed 31.7% bioremoval in the presence of 100 mg/L copper, and N5a was much more resistant to copper compared to N1c and E. coli. The isolates were identified by 16S rRNA gene sequence analysis. The 16S rRNA gene sequence of N5a showed 96%-97% similarity to Pseudomonas stutzeri and other Pseudomonas spp. The 16S rRNA gene sequence of N1c was 96% similar to Achromobacter sp., Alcaligenes sp., and a novel genus, Collimonas.