Evaluation of oxygen permeability of gas vesicles from cyanobacterium Anabaena flos-aquae

The enhancement of oxygen permeability in aqueous medium by addition of cyanobacterial gas vesicles (GVs) has been examined. The GVs were isolated from cultures of Anabaena flos-aquae that had been cultivated in photobioreactors and harvested by dark flotation. Prior to the permeability experiments, the collected GVs were treated with glutaraldehyde for improved stability. Measurements of oxygen permeability were made with a polarographic oxygen electrode in suspensions of various GV volume fractions (0-2.1%). The experimental results were compared with the values predicted theoretically (Fricke's equation) assuming different permeability through the GVs (PmGV), ranging from 0 to 8.30 x 10(-4) mol m-1 atm-1 s-1. The former corresponded to impermeable vesicles, the latter to air at 22 degrees C as if there were no vesicle wall. The best-fit value of PmGV was 9.9 x 10(-7) mol m-1 atm-1 s-1, ca. 36-fold higher than that in water. GVs were therefore very permeable to oxygen. However, the value was much lower than that predicted for air, implying the existence of wall resistance.