Biochemical and molecular characterization of proteolytic bacterial strains isolated from Jazan region, KSA with the application as an antibacterial agent

Abstract

Objectives: Biochemical and molecular characterization of proteolytic bacterial strains isolated from Jazan region, KSA with the application as an antibacterial agent. Materials and Methods: Three samples were collected from extreme environment, Jazan, KSA. Skim milk nutrient agar medium was used for protease screening for several colonies by streaking method at 37°C. API biochemical kit was used to characterize the three isolates using some selective media. The genetic identification was done using 16S rRNA gene sequencing. The sensitivity of the tested strains;Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae against the extracellular crude protease enzyme produced from the three isolated bacteria and different antibiotics was done. Results: The isolates were identified as Bacillus subtilis, Bacillus licheniformis, and Bacillus cereus. B. cereus and B. licheniformis recorded high sensitivity (71%) against most antibiotics, in addition, B. subtilis showed resistance to Aztreonam only. It was found a considerable increase in the level of both of protease activity (units/ml) and bacterial growth (colony-forming units/ml) of the cultures that were directed by the B. subtilis and B. licheniformis up to 37°C then decreased at 45°C. On the contrary, the growth of B. cereus and its activity gradually increased up to 45°C. The enzyme activity and bacterial growth of B. subtilis and B. cereus strains were increased at alkaline medium. However, B. licheniformis gave the highest growth and activity at neutral pH. In addition, it was found that the enzyme activity and bacterial growth of B. subtilis were reached to the maximum at 5% NaCl. However, the maximum bacterial growth and enzyme activity for B. licheniformis and B. cereus was at 2% NaCl. It was found high effect on inhibiting the growth of pathogenic bacteria using 5 μl of crude enzyme with specific enzyme activity 73, 76, and 92 (units/ml)/(mg protein/ml) for B. subtilis, B. licheniformis, and B. cereus, respectively. All pathogenic bacteria were totally inhibited with 10 μl of crude enzyme. Conclusion: The potential Bacillus proteases can promote new industry as antimicrobial agents.