A theoretical study on the amount of ATP required for synthesis of microbial cell material |
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Authors: | A H Stouthamer |
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Institution: | (1) Biological Laboratory, Free University, de Boelelaan 1087, Amsterdam, the Netherlands |
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Abstract: | The amount of ATP required for the formation of microbial cells growing under various conditions was calculated. It was assumed
that the chemical composition of the cell was the same under all these conditions. The analysis of the chemical composition
of microbial cells of Morowitz (1968) was taken as a base. It was assumed that 4 moles of ATP are required for the incorporation
of one mole of amino acid into protein. The amount of ATP required on account of the instability and frequent regeneration
of messenger RNA was calculated from data in the literature pertaining to the relative rates of synthesis of the various classes
of RNA molecules in the cell. An estimate is given of the amount of ATP required for transport processes. For this purpose
it was assumed that 0.5 mole of ATP is necessary for the uptake of 1 g-ion of potassium or ammonium, and 1 mole of ATP for
the uptake of 1 mole of phosphate, amino acid, acetate, malate etc. The results of the calculations show that from preformed
monomers (glucose, amino acids and nucleic acid bases) 31.9 g cells can be formed per g-mole of ATP when acetyl-CoA is formed
from glucose. When acetyl-CoA cannot be formed from glucose and must be formed from acetate, Y
ATP
MAX
is only 26.4. For growth with glucose and inorganic salts a Y
ATP
MAX
value of 28.8 was found. Addition of amino acids was without effect on Y
ATP
MAX
but addition of nucleic acid bases increased the Y
ATP
MAX
value to that for cells growing with preformed monomers. Under these conditions 15–20% of the total ATP required for cell
formation is used for transport processes. Much lower Y
ATP
MAX
values are found for growth with malate, lactate or acetate and inorganic salts. During growth on these substrates a greater
part of the ATP required for cell formation is used for transport processes. The calculated figures are very close to the
experimental values found.
The interrelations between Y
ATP
MAX
and YATP, the specific growth rate (μ), the maintenance coefficient (me) and the P/O rate are given. From a review of the literature evidence is presented that these parameters may vary under different
growth conditions. It is concluded that in previous studies on the relation between ATP production and formation of cell material
these effects have unjustly been neglected. |
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Keywords: | |
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