Distinct Adaptivity During Phosphate Uptake by the Cyanobacterium Anabaena variabilis Reflects Information Processing About Preceding Phosphate Supply

Abstract

Using a phosphate deficient population of the cyanobacterium Anabaena variabilis Kützing the adaptation of the phosphate uptake system to pulsewise increases in the external phosphate concentration has been studied. The following observations have been made:

1.	For an adaptation to occur, the external concentration had to be raised to micromolar levels. No adaptation was observed in the nanomolar concentration range.
2.	During adaptation the uptake system was transformed within a few minutes from a more active into a less active state in which uptake behavior obeyed a linear flow-force relationship over a wide concentration range.
3.	Novel adaptations were influenced in a distinct way by the outcome of previous adaptations. In consequence, adaptive alterations in kinetic and energetic properties of the phosphate uptake system, revealed during pulsewise increases in the external phosphate concentration, depend on the pattern of previous phosphate fluctuations to which the population had been exposed. This succession of adaptive events is interpreted as a primitive form of information processing about the mode of phosphate supply, performed by the growing cells.
4.	Information about nutrient fluctuations experienced by the cells of a population was transferred after cell division to daughter cells. This was shown by exposing two reference cultures, originating from the same batch of phosphate deficient cyanobacteria, to the same amount of phosphate in two different supply modes. During subsequent growth these two cultures developed distinct adaptive potentials, which were maintained over several generations, even if they were further cultivated under identical conditions. This distinct adaptive potential affected significantly the phosphate storage capacity of daughter cells.

Keywords:

• Adaptive behavior
• Anabaena variabilis
• Cyanobacteria
• Information storage
• Epigenetic inheritance
• Phosphate uptake system

Acknowledgments

The authors are grateful to the Austrian Science Fund for financial support and to the interdisciplinary workshop on “Adaptivity and Learning”, organized by FEST (Heidelberg), for stimulating discussions.