Microbiologia Médica e Diagnóstico

Cow Milk Contamination with Heavy Metals (Mercury and Lead) and the Possibility of Heavy Metals Disintegration by the Human Intestinal Bacteria

Abstract

Nastaran Soltani and Marjan Shaheli

Metal pollution in the environment and human diet represents a perennial problem and is detrimental to human health. Developed countries are seeking ways to find a solution for this problem. However, in developing countries such as Iran largely due to the lack of appropriate infrastructures, all people are exposed to the risk of heavy metals and nobody pays due attention to this problem. Bioremediation projects, in which bacteria are used, are currently an active field to solve the problem. The present study aimed to identify bacteria that might be used for disintegration of heavy metals in foods (cow's milk) in the intestines of humans. First, the amount of mercury and lead in cow's milk was determined by atomic absorption spectrophotometry and then 25 bacterial strains from the human intestine were purified and identified. After that, MIC test was conducted on the basis of resistance against heavy metals for 25 samples. To confirm the disintegration of heavy metals, bacterial biomass was isolated, and the atomic absorptions were assessed. Finally, bacterial DNAs were extracted and sequenced. The collected milk samples were contaminated with mercury and lead and 2 out of 25 collected samples were able to disintegrate heavy metals. The DNAs for the two bacteria were isolated, sequenced, and compared with other sequences in the GeneBank. The results revealed that the two isolated bacteria were new strains of E. coli. Finally, the resulting species were labeled and registered with the name of the authors in the NCBI website. Our findings indicated that two strains of E. coli were able to disintegrate heavy metals (mercury and lead) from foodstuffs (cow milk) in the intestinal tract of humans.