Al-Mustansiriyah Journal of Science ISSN: 1814-635X (print), ISSN:2521-3520 (online) Volume 30, Issue 4, 2019 DOI: http://doi.org/10.23851/mjs.v30i4.685 29 Copyright © 2019 Authors and Al-Mustansiriyah Journal of Science. This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Research Article Open Access The Biological Activity of Protein Extracts of Bacillus spp. Isolated from Soil against Some Pathogenic Bacteria Haneen A. Ibrahim * , Neihaya H. Zaki Department of Biology, College of Science, Mustansiriyah University, IRAQ *Corresponding author email: haneen_ali90@yahoo.com A r t i c l e I n f o Abstract Received 26/06/2019 Accepted 05/08/2019 Published 15/01/2020 Forty soil samples were collected from different regions in Baghdad city. Among 52 isolates, only 38 (73.1 %) belonged to Bacillus spp. All bacterial isolates were submitted to the cultural, microscopical, biochemical examination and VITEK 2 System. Bacillus cereus was the predominant (21; 55.3%) followed by Bacillus subtilis (11; 28.9%), then Bacillus amyloliquefaciens (6;15.8%). B. cereus (B1) and B. subtilis (B16) isolates showed the highest level of antibacterial activity; therefore, their extracellular proteins were extracted, purified using ammonium sulfate (80%) saturation, and submitted to Sepharose-6B gel filtration column. SDS-polyacrylamide gel electrophoresis was used to determine the molecular weights of the proteins, in which one band of molecular weight 68 and 50kDa was found in B. cereus and B. subtilis respectively. These proteins revealed high antibacterial activity on Gram positive bacteria, and moderate effect on Gram negative bacteria, except Pseudomonas aeruginosa where no effect was reported. The antibiofilm activity of the extract showed increased effect against Streptococcus pyogens, while moderate effect against each of Staphylococcus aureus, Escherichia coli, Serratia marcescens, Klebsiella spp with no impact against P.aeruginosa. The results of cytotoxicity indicated that the purified extract had a higher cytotoxic effect on the breast cancer cell line MCF7 cells at 1000μg/ml concentration, than the crude extract that showed cytotoxic effect on the same cell line at 100μg/ml. Key words: Soil samples, Bacillus spp., Proteins, Antibacterial, Antibiofilm, Cytotoxcity. ال خلصـة             .   52  ،  3X ( M3;1 )   Bacillus spp .           VITEK 2 .   Bacillus cereus   ( 21   55;3 )  Bacillus subtilis ( 11 ؛2X;c ) ،  Bacillus amyloliquefaciens ؛15;X .)   B. cereus (B1)  B. subtilis (B16)       .  ،         ،        ( X0 ) ،         Sepharose-6B .      SDS- polyacrylamide gel electrophoresis     ،           6X  50     B. cereus  B. subtilis   .              ،        ، ء Pseudomonas aeruginosa      .      ء   ً  ً  Streptococcus pyogens ،             ،   ،     ،         P.aeruginosa .                  MCF7     1000  /                 100  /  . Introduction Antibiotics, naturally formed by microorganisms are responsible for the control and regulation of microbial population in soil, compost and water. The majority of antibiotics are toxic in nature and only a few are used in medicine for treatment of multiple diseases due to their high safety [1]. Bacterial secondary metabolites or bioactive compounds have structural diversity obtained from natural