Analysis of pressure-collapse curves of Halobacterium cells containing gas vesicles and of gas vesicles released from such cells by hypotonic lysis shows that the isolated gas vesicles are considerably weaker than those present within the cells: their mean critical collapse pressure was around 0.049-0.058 MPa, as compared to 0.082-0.095 MPa for intact cells. The hypotonic lysis procedure, which is widely used for the isolation of gas vesicles from members of the Halobacteriaceae, thus damages the mechanical properties of the vesicles. The phenomenon can possibly be attributed to the loss of one or more structural gas vesicle proteins such as GvpC, the protein that strengthens the vesicles built of GvpA subunits: Halobacterium GvpC is a highly acidic, typically "halophilic" protein, expected to denature in the absence of molar concentrations of salt.
Bibliographical noteFunding Information:
We are grateful to A.E. Walsby (University of Bristol) and to two anonymous reviewers for helpful comments. We further thank the staff of the Interuniversity Institute for Marine Sciences of Eilat for logistic support. This study was supported by the Israel Science Foundation (Grant No. 504/03).
- Gas vesicles