Adaptation of the Cyanobacterium Anabaena variabilis to Low CO2 Concentration in Their Environment

Abstract

The rate of adaptation of high CO₂ (5% v/v CO₂ in air)-grown Anabaena to a low level of CO₂ (0.05% v/v in air) was determined as a function of O₂ concentration. Exposure of cells to low (2.6%) O₂ concentration resulted in an extended lag in the adaptation to low CO₂ concentration. The rate of adaptation following the lag was not affected by the concentration of O₂. The length of the lag period is markedly affected by the O₂/CO₂ concentration ratio, indicating that the signal for adaptation to low CO₂ may be related to the relative rate of ribulose-1,5-bisphosphate carboxylase/oxygenase activities, rather than to CO₂ concentration proper. This suggestion is supported by the observed accumulation of phosphoglycolate following transfer of cells from high to low CO₂ concentration.