Glutaraldehyde Treatment of Proteinaceous Gas Vesicles from Cyanobacterium Anabaena flos-aquae

As potential gas microcarriers, gas vesicles (GVs) were isolated from cultures of the fAilamentous cyanobacterium Anahaena flos-aquae and treated with glutaraldehyde. The effects of glutaraldehyde treatment on the stability of GVs, against elevated temperatures (40-121 °C) and protein-stripping agents such as urea and sodium dodecyl sulfate (SDS), were then examined with the pressure collapse curves generated using pressure nephelometry. The treatment was very beneficial to GVs against the exposure to SDS and urea; however, it did not make the evolution-optimized vesicle structure stronger or more temperature-resistant. In the presence of these proteinstripping agents, the treated vesicles had higher median (50%) collapse pressures (by >1 atm) than the untreated ones, at both room temperature and 40 °C. This increase has been presumably attributed to the cross-linking of the large GvpC protein to the ribbed GvpA shell, thereby resisting the stripping of GvpC that provides the primary mechanical strength to the vesicle wall. The glutaraldehyde treatment also restored the strength of GVs weakened by a 5-week storage in a refrigerator and, therefore, is expected to improve the stability of GVs for long-term storage. GVs could not be autoclaved. If necessary for the intended applications, glutaraldehyde treatment may also serve to chemically sterilize the vesicles, with the glutaraldehyde subsequently removed by dialysis.