Antimicrobial, antiparasitic and antiproliferative effects of the extract of Bacillus safensis SG-32 isolated from a Brazilian oil reservoir

Strains previously isolated from offshore oil reservoirs in Campos Basin (RJ, Brazil) and Potiguar Basin (RN, Brazil) were tested for production of antimicrobial compounds. Sixteen bacteria produced compounds with antimicrobial activity. The strain chosen for further study was Bacillus safensis SG-32 based on its ability to inhibit 76% of the strains tested. The bacterium was grown in Marine Broth (MB) and the hexane extract was investigated for minimal inhibitory concentration (MIC) (highest activity 0.4 mg/mL against Staphylococcus aureus), antiproliferative activity against human cancer cell lines (highest activity TGI = 69.83 µg/mL against melanoma cell lines), and antiparasitic tests (maximum activity 22.49% against Trypanosoma cruzi). Bioactive extract from B. safensis SG-32 was purified using silica column chromatography. Fractions collected were tested by bioautography in order to select the fraction with antimicrobial activity. The active molecule was identified by Nuclear Magnetic Resonance (NMR) as a diterpene of the Cyathin family. In addition to the antimicrobial and antitumor activity, Cyathin type compounds are known to stimulate the synthesis of Nerve Growth Factor (NGF), a capacity that implicates their potential as therapeutic agents to treat neurodegenerative ailments such as Alzheimer’s or Parkinson’s disease. In conclusion, this study showed that B. safensis SG-32 produces metabolites with antibacterial, antiproliferative and antiparasitic activities, and opens perspectives for further study of its potential also for nerve protection.