Ag. Degermendzhi et al., A NEW EXPERIMENTAL-METHOD TO REVEAL DENSITY-DEPENDENT CHEMICAL FACTORS INVOLVED IN MICROBIAL-POPULATION GROWTH-CONTROL, Microbiology, 62(3), 1993, pp. 308-313
Experiments based on an earlier developed theory with a culture of Esc
herichia coli 0-124 were undertaken to determine the feedback strength
(FBS) in growth control. FBS is defined as the change in growth accel
eration brought about by a discontinuous reduction in microbial concen
tration under conditions of constant chemical composition of the mediu
m, and is an over-all measure of the regulatory influence of all chemi
cal factors dependent on biomass concentration. FBS was determined for
batch cultivation with glucose. In various growth phases the culture
was diluted by its own filtrate and then the change in growth accelera
tion as compared to the control was measured. FBS was reliably differe
nt from zero at the end of the exponential phase and in the phase of d
ecelerated growth and was of the order of -20 to -200 (h.g/liter)(-1).
The feedback component due to glucose alone was estimated using the o
btained relation between specific growth rate and glucose concentratio
n (mu(max) = 0.55 +/- 0.05 h(-1), K-s = 2.5 +/- 0.7 mg/liter). The glu
cose-dependent regulatory contribution to FBS was found to be as low a
s 0.5 to 40%, which suggests the presence of other growth control fact
ors. Upon accuracy improvements, this method may develop into an accep
ted microbiological tool for identifying major density-dependent facto
rs involved in microbial growth control.