The extremely halophilic archaebacterium, Halobacterium halobium, has the capability to synthesize intracellular gas-filled vesicles for buoyancy to regulate the availability of light and oxygen. The mutation rate for gas vesicle synthesis (Vac) is the highest of several phenotypic hypervariabilities observed in H. halobium. The Vac mutation rate (1%) is 100-fold higher than for the well-characterized purple membrane mutations which are the result of insertional inactivation of the bacterio-opsin (bop gene (DasSarma, et al., unpublished), we are now in an ideal position to study the mutation, structure, and regulation of the gvh gene using standard methods of molecular genetics. We plan to: (a) examine the physical and transcriptional state of the gvh gene region in many Vac mutants by Southern and Northern hybridizations; and (b) complete the DNA sequence of the gvh gene region and determine the structure of the mRNA by mapping with S1 nuclease and capping enzyme.
