TY - JOUR
T1 - The optimal strategy for the metabolism of reserve materials in micro-organisms
AU - Parnas, Hanna
AU - Cohen, Dan
PY - 1976/1
Y1 - 1976/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0017073575&partnerID=8YFLogxK
U2 - 10.1016/S0022-5193(76)80044-6
DO - 10.1016/S0022-5193(76)80044-6
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C2 - 772317
AN - SCOPUS:0017073575
SN - 0022-5193
VL - 56
SP - 19
EP - 55
JO - Journal of Theoretical Biology
JF - Journal of Theoretical Biology
IS - 1
ER -