Bubble formation properties of hydrophobic particles in water and cells of Tetrahymena.

It is generally assumed that hydrophobic surfaces play a role in bubble formation in vivo, but no tests of this assumption seem to exist. Model systems for both in vitro and in vivo study of the bubble nucleation properties of hydrophobic surfaces were developed. First, aqueous suspensions of particles were exposed to gas supersaturations, and the numbers of bubbles that formed were determined. Although the supersaturation thresholds for spontaneous bubble nucleation in pure water exceeds 175 atmospheres gas tension, gas tensions of only a few atmospheres caused the profuse formation of bubbles with the most effective particles. Some or most of this latter effect seemed to be caused by gas trapped in irregularities on the particles. Second, particles that were especially effective bubble promoters were added to suspensions of ciliates. Upon their ingestion, all of the particles lost their ability to induce bubble formation in the cells with supersaturations equal to or exceeding the threshold for spontaneous nucleation in water. These results indicate that intracellular bubble formation may not occur readily in vivo.