Phenotypic characterization and correlation analysis of heavy metal tolerant bacteria

Abstract

High concentrations of metals strongly influence the composition of soil microflora. Tanneries being one of major sources of metal pollution in Pakistan pose serious threat to the soil bacterial communities. Present study aimed to investigate the bacterial diversity from tannery effluents affected soil. Total Sixteen bacterial isolates were purified and characterized morphologically and biochemically. All selected isolates were facultative anaerobes and able to grow in wide pH ranges from 5-11. Only TS3, TS4, TS8, TS9, TS13 were resistant to Erythromycin. On the basis of phenotypic characters, cluster analysis was done to determine the similarities among selected bacterial isolates using Jaccord's (SJ) coefficients by UPGMA clustering algorithm. Two major clusters while eight subgroups of selected isolates were obtained on the basis of similarity indices. Bacterial isolates in present research were tolerant to the higher concentrations of lead, chromium and cadmium up to 1000μg/ml. Variable level of resistance was observed against nickel, manganese, copper and iron, while mercury, zinc and cobalt was toxic to these bacteria at higher concentrations. Pearson correlation analysis revealed a strong correlation among some heavy metals as well as antibiotics. Moreover, strong negative correlation was also observed between few antibiotics and heavy metals. The heavy metal profiling indicated the potential of these bacterial isolates to be used in bioremediation of heavy metal polluted soils after further research on their genetic mechanisms.