Crystallization of an Isoprenoid from Host-Independent Bdellovibrio bacteriovorus for X-Ray Diffraction Analysis
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Gram-negative Bdellovibrio bacteriovorus in its host-dependent (HD) phenotype is a predator bacterium that invades other Gram-negative bacteria. Following a facile, rapid selection method developed in our laboratory, host-independent (HI) Bdellovibrio bacteriovorus is obtained by spotting an aliquot of a traditional host-dependent Bdellovibrio prey lysate (with E. coli prey) on filter paper over nutrient-rich agar. These HI bdellovibrios, which do not need prey to survive and which exhibit pleiomorphic morphology, appear yellow. Thus, an extraction protocol was created to isolate the membrane-bound natural products. The extraction protocol leads finally to a supernatant that contains the isoprenoid among other compounds. Previous structural measurements in our laboratory have shown (NMR, LC-MS, high resolution MS-MS) that (1) the structure has a polar end connected to a linear chain of seven isoprenoid units, (2) the mass is 726.5548 amu, and (3) the empirical formula is C44H74N2O6. In this investigation, the remaining supernatant is further treated in order to form small, single crystals for X-ray analysis. Such analysis would finalize the structure determination thus far obtained by NMR and would also provide stereochemical information. Preliminary results for crystal formation will be presented. Although the biological role of this isoprenoid in the HI phenotype remains unknown, we speculate that it may serve as a biosurfactant or increase membrane fluidity.