Halobacterium sp. gas vesicle gene cluster and thin-sections. (A) Genetic map of the gas vesicle gene cluster from Halobacterium sp. NRC-1 pNRC100 is shown with genes transcribed rightward colored red and genes transcribed leftward colored blue . The scale is noted above (divided into kilobase pairs) and the positions of the gvpC deletion (Δ) and kappa insertion (κ) are indicated. (B) and (C) Thin sections of Halobacterium sp. NRC-1 (B) and SD109 (pFM104gvpC::κ1) mutant (C) viewed by transmission electron microscopy (bar, which is 325 nm long, applies to both B and C). Gas vesicles are visible as empty oval or spindle-shaped regions. Shapes observed reflect different planes of sectioning.