Screening for the presence of the metallothionein gene in bacteria isolated from mines and industrial wastewater in Isfahan province, and investigating the biochemical and microbial characteristics of the isolated variants

BACKGROUND AND OBJECTIVESExcessive accumulation and circulation of heavy and toxic metals in the environment have raised environmental and health concerns. Nowadays, bioremediation processes utilizing natural microorganisms for detoxification of hazardous metals that pose threats to human health and the environment have gained attention. This study focuses on the detection of the metallothionein gene in bacteria isolated from mines in Isfahan. Evaluating the biochemical and microbiological characteristics of these bacteria can contribute to the identification of microbial strains with high bioremediation capabilities.MATERIALS AND METHODSSampling and cultivation were conducted from approximately ۹۰ different locations of iron smelting factories and stone mines in Isfahan. The colony PCR method was used for the detection of the metallothionein gene. The resistance level of the isolates to heavy metals was examined using MIC and MBC tests. All microbial characteristics, particularly drug resistance and biochemical properties, were evaluated. Ultimately, three highly resistant strains to cadmium, copper, and nickel were identified based on the ۱۶S rRNA gene sequence and registered in the genomic database.RESULTS AND DISCUSSIONThe highest resistance levels of the strains to cadmium, copper, and nickel were calculated as ۳.۸, ۲.۶, and ۱.۵ milligrams per milliliter, respectively. Moreover, the resistance pattern of the metal-resistant strains to antibiotics indicated that most of them were also resistant to common antibiotics. Finally, one Gram-negative bacillus strain belonging to the Pseudomonas genus and two Gram-positive bacillus strains belonging to the Bacillus genus, all exhibiting high resistance to antibiotics and heavy metals, were identified and registered. Additionally, some biochemical characteristics showed significant differences between the metal-resistant bacteria and other variants.CONCLUSIONSince microorganisms play a crucial role in bioremediation, tracking metallothionein-encoding genes in bacteria is of significant importance. High resistance to antibiotics in bacteria exhibiting higher resistance to heavy metals should be given attention.