Identification and characterization of heavy metal-resistant bacteria selected from different polluted sources

The present study deals with the isolation, the identification, and the characterization of heavy metal-resistant bacteria selected from several polluted sources with the aim of using them as bioremediation agents of contaminated sites by heavy metals. Four protocols were used in a different way to select the maximum of isolates resistant to heavy metals. Isolates obtained, according to the fourth selection protocol by using the free nutrients medium, showed the highest values of minimum inhibitory concentration (MIC), and it can be deduced from this last result that when the bacteria are subjected to stressful conditions they develop a system that will enable them to withstand high levels of heavy metals. The study of the MIC at all resistant isolates allowed determining that the order of toxicity of the different metals was as follows: Cu > Cr > Cd > Ni > Zn > Co. These metals might exert varying effects depending on their adsorption and their complexation capacities to the bacterial cell wall. ...