Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 13 3 2021 06 05 372 380 Sepideh Asadi Department of Microbiology and Microbial Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran Neda Soleimani Department of Microbiology and Microbial Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran Zahra Khosravi Babadi Department of Microbiology and Microbial Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran Gholam Hossein Ebrahimipour Department of Microbiology and Microbial Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran 2020 08 26 2021 03 21 Background and Objectives: Cancer incidence and recurrence, antibiotic resistance, and overuse of antibiotics have become a global concern. The purpose of this study was to identify and isolate bacteria from the skin of the Rana ridibunda, Iranian swamp frog, which has produced antimicrobial compounds, and investigate its cytotoxic activity on the breast (MCF7) and glioblastoma (U87) cancer cell line. Materials and Methods: An antibiotic-producing bacterium was isolated from the frog skin. The bacterium was identified based on 16S rDNA sequencing and biochemical and morphological characteristics. Antimicrobial activity of the culture supernatant was examined by disc diffusion and MIC methods. Cytoplasmic and cell wall extracts of bacteria were prepared by sonication. SDS-PAGE was then used to examine protein contents of them. The cancer cell lines were treated with cytoplasmic and cell wall extracts at different concentrations. The effects of cytotoxicity were assessed by MTT assay at 24 and 48 h intervals. Finally, the results were analyzed by SPSS. Results: The isolated bacterium was identified as a new strain of Bacillus atrophaeus. MIC and disc diffusion methods showed that the Bacillus atrophaeus antimicrobial activity was broad spectrum. MTT assay showed IC50 values 30 μg/ml and 20 μg/ml for U87 and MCF7 cells after 24-48 h exposure, respectively. Conclusion: The cytoplasmic extracts of Bacillus atrophaeus has anticancer potential and can be used as an alternative or complementary candidate in the treatment of cancer. Further in vivo and in vitro mechanistic studies are suggested to confirm the biological activities. https://ijm.tums.ac.ir/index.php/ijm/article/view/2760 https://ijm.tums.ac.ir/index.php/ijm/article/download/2760/1355