Pages: 20-28

Abstract

The aim of this study was to screen antibacterial, antifungal and cytotoxic activities of crude metabolites of a bacterium DADA-1AIMR-24 isolated from soil in Rajshahi division, Bangladesh. The antibacterial activity of crude extracts was tested by agar well diffusion technique against Bacillus cereus, Staphylococcus aureus ATCC-259233, Listeria monocytogenes, Agrobacterium spp., Escherichia coli FPFC-1407, Shigella dysenteriae AL-35587, Shigella sonnei and Shigella boydii. At the same time, antifungal activity was also conducted by disc diffusion method against Aspergillus niger, Tichoderma herzanium, and Microphomina phaseolina. The MIC values of the extract against Bacillus cereus, Staphylococcus aureus ATCC-259233, E. coli FPFC-1407, Shigella dysenteriae AL-35587, Shigella sonnei, Shigella boydii were 64, 64, 64, 64, 64 and 32 µg/ml respectively. The minimum bactericidal concentration (MBC) was also determined (Table 2). The MBC values of the extract were 128, 128, 128, 128, 128 and 64 µg/ml. As the MBC value was higher than the MIC value, it is clear that the extract was bacteriosatic not bactericidal. The approximate counts of bacteria in the MIC tubes were also determined (table 2). The brine shrimp lethality bioassay was conducted to determine the cytotoxic nature of crude extracts, which showed that the degree of lethality of extracts was directly proportional to the concentration (LC50 21.55 μg/ml) compounds in the crude extract but due to low production of metabolites, we could not extract sufficient amounts as it took long time to produce metabolites. Further work is necessary to isolate and characterize the active compounds.