Antimicrobial Activity and GC-MS Analysis of Bioactive Constituents of Thermophilic Bacteria Isolated from Saudi Hot Springs

The bioactivity of thermophilic bacteria isolated from hot springs in the southern region of Saudi Arabia was investigated. Of the 84 bacterial isolates, the antimicrobial activity of 50 of them had an antagonistic effect against one or more of the tested human pathogens: Candida albican, Staphylococcus aureus, Proteus mirabilis, Klebsiella pneumonia and Shigella flexneri. Furthermore, four isolates exhibited the highest antagonistic ability against all pathogens. The molecular identification of selected promising isolates and phylogenetic analysis confirmed the accurate identity of the isolates as Bacillus sonorensis, Bacillus thermocopriae, Brevibacillus borstelensis and Brevibacillus parabrevis. GC-MS analysis of the cell-free extracts detected 40 secondary metabolites; each strain has its own secondary metabolites in addition to other compounds that are of industrial and pharmaceutical importance. The major secondary metabolites produced were cyclohexyl acrylate, imiloxan, tabtoxinine-beta-lactam, nicotinyl alcohol, mephenesin, etomidate, L-menthyl lactate, (3-aminopropyl) dibutylborane, filbertone, and 1-dotriacontanol. These findings suggest a need to raise awareness of the value hot springs in Saudi Arabia have as locations for isolating thermophilic bacteria that could possibly serve as reservoirs for new bioactive compounds of industrial and medical importance.