U. Von Stockar et Js. Liu, Does microbial life always feed on negative entropy? Thermodynamic analysis of microbial growth, BBA-BIOENER, 1412(3), 1999, pp. 191-211
Schrodinger stated in his landmark book, What is Life?, that life feeds on
negative entropy. In this contribution, the validity of this statement is d
iscussed through a careful thermodynamic analysis of microbial growth proce
sses. In principle, both feeding on negative entropy, i.e. yielding product
s of higher entropy than the substrates, and generating heat can be used by
microorganisms to rid themselves of internal entropy production resulting
from maintenance and growth processes. Literature data are reviewed in orde
r to compare these two mechanisms. It is shown that entropy-neutral, entrop
y-driven, and entropy-retarded growth exist. The analysis of some particula
rly interesting microorganisms shows that enthalpy-retarded microbial growt
h may also exist, which would signify a net uptake of heat during growth. H
owever, the existence of endothermic life has never been demonstrated in a
calorimeter. The internal entropy production in live cells also reflects it
self in the Gibbs energy dissipation accompanying growth, which is related
quantitatively to the biomass yield. An empirical correlation of the Gibbs
energy dissipation in terms of the physico-chemical nature of the growth su
bstrate has been proposed in the literature and can be used to predict the
biomass yield approximately. The ratio of enthalpy change and Gibbs energy
change can also be predicted since it is shown to be approximately equal to
the same ratio of the relevant catabolic process alone. (C) 1999 Elsevier
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