The optimal strategy for the metabolism of reserve materials in micro-organisms

Hanna Parnas*, Dan Cohen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

A model of the optimal policy for the metabolism of storage materials in micro-organisms in different environments is presented, assuming that it maximizes long term survival. (1) Deterministic environments: an environment in which pulses of low and high substrate concentrations alternate, the optimal level of storage materials increases when the variability of the environment increases. In an environment in which a substrate pulse is followed by starvation, the optimal level of storage materials increases when the death rate or the duration of starvation increases. The optimal level decreases with increasing duration of the pulse and with increasing level of rRNA before the starvation period. The dominant optimal policy is to synthesize enough storage materials for complete survival during the starvation period. In an environment in which a substrate pulse appears, the concentration falls gradually, and starvation follows only after a period of low and falling concentration, the optimal level of storage materials is usually that needed for complete survival during starvation. The synthesis will take place toward the end of the growing period, since the decrease in concentration is a signal for the coming starvation. (2) Probabilistic environments: even when the probability for starvation is quite low, it is optimal to synthesize enough storage materials to provide for a complete survival during the starvation period. The current hypothesis, that storage materials are synthesized only when there is a surplus of energy at the time, irrespective of the future needs of the cells, is criticized. The evidence supports the hypothesis that the synthesis of storage materials is according to an optimal policy which takes into account both the present cost and the future requirements for energy.

Original languageEnglish
Pages (from-to)19-55
Number of pages37
JournalJournal of Theoretical Biology
Volume56
Issue number1
DOIs
StatePublished - Jan 1976

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