Gas Compartments Research Articles

Reactions of the flagellate Astasia longa in gradients of dissolved carbon dioxide.

An apparatus is described for the study of micro-organisms in a gradient of concentrations of a dissolved gas. The organisms are mounted in a thin layer of water bounded above and below by glass. A gradient is set up from side to side across the film, between two gas compartments flushed with different gas mixtures. Astasia longa accumulates at a ‘preferred’ tension of dissolved carbon dioxide. The ‘preferred’ tension depends on the alkali reserve of the medium, and can be interpreted in terms of a preference for a pH of between 5·3 and 6·3. There is no direct relation between the behaviour of Astasia and the concentration of CO 2 , H 2 CO 3 , HCO' 3 , or CO'' 3 .