Abstract
In this research fifty Actinobacteria isolates were obtained from soil samples collected from desert sites in the Kingdom of Saudi Arabia. The isolates were purified and exposed to a variety of biochemical and physiological tests to determine their tentative taxonomy. Color group was determined for all 50 strains and a total of 13 different groups were allocated as follows: 24% gray, 10% chalky white, 12% light gray, 12% dark gray, 10% light brown, 2% yellow, 2% whitish pink, 2% whitish yellow, 2% dark red, 2% pale gray, 6% pale yellow, 6% pale white and 8% grayish white. Bioactive compounds were extracted from each isolate using methanol as solvent; these were then tested against Staphylococcus aureus ATCC 13076, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 2592, Pseudomonas aeruginosa ATCC 27583, Salmonella suis ATCC 13076, Shigella sonnei ATCC 11060 and Candida albicans ATCC 10231. Whole extracts of the isolates which exhibited inhibitory activities against the seven microorganisms were chosen for gas chromatography mass spectrometry (GC-MS) analysis. This showed that the predominant inhibitory compound in all extracts was 2, 3-butanediol, [R-(R*, R*)], while cyclobutanol and octadecanal were also present in most isolates. Based on the cultural, physiological and biochemical tests as well as scanning electron microscopy studies, all the selected isolates were members of the Genus Streptomycetes.