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

The enhancement of oxygen permeability in aqueous medium by addition of cya nobacterial gas vesicles (GVs) has been examined. The GVs were isolated fro m cultures of Anabaena flos-aquae that had been cultivated in photobioreact ors 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 exper imental results were compared with the values predicted theoretically (Fric ke's equation) assuming different permeability through the GVs (Pm,,), rang ing from 0 to 8.30 x 10(-4) mol m(-1) atm(-1) s(-1). The former corresponde d to impermeable vesicles, the latter to air at 22 degrees C as if there we re no vesicle wall. The best-fit value of Pm-GV was 9.9 x 10(-7) mol m(-1) atm(-1) s(-1) ca. 36-fold higher than that in water. GVs were therefore ver y permeable to oxygen. However, the value was much lower than that predicte d for air, implying the existence of wall resistance. (C) 2000 Elsevier Sci ence B.V. All rights reserved.