Gas vesicles are small, hollow, gas filled protein structures found in several cyanobacterial and archaebacterial microorganisms [<cite idref="PUB00000481"/>]. They allow thepositioning of the bacteria at the favorable depth for growth. Gas vesiclesare hollow cylindrical tubes, closed by a hollow, conical cap at each end.Both the conical end caps and central cylinder are made up of 4-5 nm wideribs that run at right angles to the long axis of the structure. Gas vesiclesseem to be constituted of two different protein components: GVPa and GVPc.GVPc is a minor constituent of gas vesicles and seems to be located on theouter surface. Structurally, cyanobacterial GVPc consists of four or fivetandem repeats of a 33 residue sequence flanked by sequences of 18 and 10residues at the N- and C-termini, respectively.