Efficient inhibition of some multi-drug resistant pathogenic bacteria by bioactive metabolites from Bacillus amyloliquefaciens S5I4 isolated from archaeological soil in Egypt

Sixty-eight bacterial cultures were isolated from 5 archaeological soils in Egypt. It is necessary to characterize bacteria from ancient temples to develop protection programs for such archaeological places. Purified bacterial cultures were then tested for their capability to inhibit some multi-drug resistant (MDR) pathogenic bacteria including Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Escherichia coli and Klebsiella pneumoniae. Among the most active 10 antibacterial isolates, only one isolate designated as S5I4 was selected, characterized and identified as belonging to Bacillus amyloliquefaciens. The strain identification was confirmed by amplification of its 16S rRNA gene. The partial nucleotide sequence of the amplified 16S rRNA gene of the tested strain was submitted in GenBank with accession number AB813716. The physical and nutritional parameters were optimized to improve the production of antimicrobial agents by the B. amyloliquefaciens S5I4. The maximum antagonistic effect of this strain against the tested MDR pathogenic bacteria was achieved in presence of 1% galactose and 0.5% yeast extract at 37°C and pH 7.0 after 48 h incubation. The antibacterial compounds of B. amyloliquefaciens S5I4 were extracted, purified and characterized using spectroscopic analysis (IR, UV, proton NMR and MS). The compound having inhibitory activity was identified as butanedioic acid, octadecyl,1(1carboxy1methylethyl) 4octyl ester.