GAS VESICLE GENES IDENTIFIED IN BACILLUS-MEGATERIUM AND FUNCTIONAL EXPRESSION IN ESCHERICHIA-COLI

Gas vesicles are intracellular, protein-coated, and hollow organelles found in cyanobacteria and halophilic archaea. They are permeable to a mbient gases by diffusion and provide buoyancy, enabling cells to move upwards in liquid to access oxygen and/or light. In halobacteria, gas vesicle production is encoded in a 9-kb cluster of 14 genes (4 of kno wn function). In cyanobacteria, the number of genes involved has not b een determined. We now report the cloning and sequence analysis of an 8,142-bp cluster of 15 putative gas vesicle genes (gvp) from Bacillus megaterium VT1660 and their functional expression in Escherichia coli. Evidence includes homologies by sequence analysis to known gas vesicl e genes, the buoyancy phenotype off. coli strains that carry this grp gene cluster, the presence of pressure-sensitive, refractile bodies in phase contrast microscopy, structural details in phase-constrast micr oscopy, structural details in direct interference-contrast microscopy, and shape and size revealed by transmission electron microscopy. In B . megaterium, the gvp region carries a cluster of 15 putative genes ar ranged in one orientation; they are open reading frame 1 and gvpA, -P, -Q, -B, -R, -N, -F, -G, -L, -S, -K, -J, -T, and -U, of which the last II genes, in a 5.7-kb gene cluster, are the maximum required for gas vesicle synthesis and function in E. coli. To our knowledge, this Is t he first example of a functional gas vesicle gene cluster in nonaquati c bacteria and the first example of the interspecies transfer of genes resulting in the synthesis of a functional organelle.