Characterization of heavy metal and antibiotic-resistant bacteria isolated from polluted localities in Egypt

Objective The aim of this study was to isolate and identify heavy metal-resistant and antibiotics-resistant bacteria from contaminated samples (wastewater and soil) collected from different industrial areas in Egypt and determine their role in heavy metal removing. Materials and methods Samples were collected from Helwan and 10th of Ramadan city areas and enriched in culture broth containing 200, 100, and 10 ppm of arsenic (As), lead (Pb), and cadmium (Cd) as AsHNa 2 O 4 ·H 2 O, Pb(NO 3 ) 2 , and CdSO 4 , respectively. The highly resistant isolate (ST6) was selected and identified biochemically and also subjected to 16S rDNA sequencing. The growth parameters were optimized and the maximum tolerable concentration of the respective metals as well as the antibiotic resistance was determined. Result and conclusion After enrichment culture we isolated and purified 20 bacterial isolates resistant to the respective heavy metals As, Pb, and Cd. The morphological, biochemical, and phylogenetical characteristics of the most resistant bacterial isolates (ST6) were studied. The results showed that this isolate belongs to the species Pseudomonas stutzeri. The optimum temperature was 35°C, whereas the optimum pH was in the range of 6-7. Maximum tolerable concentration values for As, Pb, and Cd were 3500, 1750, and 50 ppm, respectively. Also, the isolate ST6 showed resistance against different antibiotics. The metal removal ability was 42.5, 57.1, and 52.9% of As, Pb, and Cd, respectively. It was concluded that the ST6 isolate was resistant and removed high concentrations of As, Pb, and Cd. Hence, this isolate may play a role in bioremediation processes of heavy metal in polluted areas.