Sahar Wefky Mostafa Hassan
Marine Microbiology Department, National Institute of Oceanography and Fisheries,
A total of 11 bacteria were isolated from sea water and screened for their antibacterial activity against five bacterial pathogens. The most potent isolate (S1) was identified as Bacillus cereus S1 using 16S rRNA sequence analysis. B. cereus S1 exhibited antibacterial potentiality against, Pseudomonas florescence, P. aeruginosa, Staphylococcus aureus, Vibrio damsela and Aeromonas hydrophila. The inhibition zones diameter were 11, 12, 12, 12 and 16 mm respectively. Maximization of the productivity with 1.3 fold increase was achieved using Plackett Burman experimental design. The optimized medium was formulated as (g/l): peptone, 7; beef extract, 1.5; sea water concentration (50%) with pH 5 and inoculum size (0.5ml for each 25 ml medium) and incubated for 12 h. Immobilization using adsorption on pumice improved the productivity by 1.6 fold compared to the basal medium while loss of antibacterial activity was up on using entrapment technique. The bioactive compounds were characterized by thermal stability even at 100 oC while they were inactivated up on exposing to ultraviolet radiation for 20 min. Moreover, the anticoagulant activity of B. cereus S1 was tested using activated Partial Thromboplastin Time (APTT) and Prothrombin Time (PT) tests. It succeed to prolong the clotting time to 40 sec and 253 sec respectively which represents about 3.3 fold and 7.2 fold compared to the control. Hexane extract was compared with other standard antibiotics and it was superior in its antibacterial effect. The crude extract of
B.cereus S1 was analyzed using gas chromatography–mass spectrometry (GC–MS). The
main constituents were Cycloheptasiloxane, tetradecamethyl-, cyclooctasiloxane
hexadecamethyl-, cyclononasiloxane octadecamethyl- , Heptasiloxane, hexadecamethyland
1,2-Benzenedicarboxylic acid, diisooctyl ester (phthalate).
Keywords: Antibacterial, Anticoagulant, Antiinflammatory, Bacillus cerus S1.