Isolation of metal tolerant bacteria from polluted wastewater

Abstract

Screening of standing and flowing water sample from Malaysian gold mine environment yielded 24 single colonies and all isolates were assessed for their metal tolerance capability. A preliminary screening on Chloride Free Medium (CFM) agar plate supplemented with 5mM of Cu2+, Ag+ and Zn2+ showed that two isolates were tolerant towards Cu2+ ion, while two other isolates were tolerant towards Zn2+ ion and one single isolate was tolerant towards Ag+ ion. Partial identification by 16S rRNA determined that they are only two distinct species of bacteria, namely, Bacillus sp. and Achromobacter sp. The identification was supported by physical and biochemical characterizations which showed that Bacillus sp. was a positive rod while Achromobacter sp. was a gram negative coccus. Maximum tolerance concentrations (MTC) of Bacillus sp. and Achromobacter sp. were determined in liquid CFM medium and the results showed that Bacillus sp. could tolerate up to 20 μM Cu2+ ion and 2.5 mM Zn2+ ion, while Achromobacter sp. could tolerate up to 5 μM Ag+ and 20μM Cu2+ ion.