Isolation and characterization of heavy metal resistant halophilic and halotolerant bacteria from the Lut desert

 Heavy metal pollution has increased worldwide. Bioremediation of toxic heavy metals in saline environments with conventional microbiological treatment processes is not feasible. Therefore, the use of halophilic and halotolerant bacteria need to be considered for the remediation of saline ecosystems. This study aimed to isolate and characterize toxic heavy metal-resistant and halophilic/halotolerant bacteria from the Lut desert.

 After sampling, halophilic/halotolerant bacteria were isolated on Moderate Halophilic media. Morphological and biochemical characterizations of isolates were carried out. Each isolate's heavy metal resistance was identified by an agar dilution method and the Minimum Inhibitory Concentrations (MIC ) of each heavy metal was determined. Then, sixteen strains were randomly selected and subjected to 16S rRNA gene identification.

 The least toxicities were found with selenite and arsenate on 74 selected isolates, while mercury exhibited the highest toxicity. The maximum MIC values of cadmium, copper, and  chromium were the same. Although, the MIC value of zinc was significantly less. The remarkable resistance toward lead, selenite, and arsenate was reported. Phylogenetic analysis revealed that most strains belong to the Bacillaceae family and Bacillus genus. 

Selected halophilic/halotolerant bacteria from the Lut desert had considerable  resistance to heavy metals. Therefore, these strains could be considered for further investigations of the mechanisms involved in heavy metal resistance of halophilic and halotolerant bacteria or for bioremediation of polluted saline environments.