A strain of Bacillus methylotrophicus was isolated from a soil sample collected in Aswan eastern desert, which is known for its extremely arid climate. After fermentation of the strain in liquid culture and subsequent extraction, a bioassay-guided isolation procedure yielded five compounds: 2-benzyl-4H-pyran-4-one, named bacillopyrone (1), pyrophen (2), macrolactin A (3) and the cyclopeptides malformin A1 (4), and bacillopeptin A (5). The structures were determined by interpretation of nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HR-MS) data. This is the first report on the isolation of compounds 1 and 2 from Bacillus species; compound 1 was reported previously as synthetic product. Bacillopyrone (1) exhibited moderate activity against the Gram-negative Chromobacterium violaceum with minimum inhibitory concentration 266.6 μg/mL, while macrolactin A (3) and malformin A1 (4) inhibited Staphylococcus aureus (minimum inhibitory concentrations 13.3 and 133.3 μg/mL, respectively).
Soleiman E. Helaly gratefully acknowledges the Alexander von Humboldt Foundation for funding this study. The authors are grateful to Wera Collisi for conducting the bioassays and Christel Kakoschke for recording the NMR spectroscopic measurements. The authors are grateful also to Prof. Abdel-Aziz Tantawy, the director of the Unit of Environmental Studies and Development at Aswan University, for providing facilities in the unit laboratories.
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The online version of this article offers supplementary material (https://doi.org/10.1515/znc-2018-0093).
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