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Appl. Environ. Microbiol., Sep 1996, 3319-3324, Vol 62, No. 9
C Guillou and JF Guespin-Michel
The variations in the maximal specific growth rate of the psychrotrophic
bacterium Pseudomonas fluorescens MF0 with respect to temperature were
studied between 0 and 30 degrees C (optimal for growth). The Arrhenius plot
showed a drastic change in slope at the intermediate temperature of 17
degrees C. Over the cold domain from 0 to 17 degrees C, the temperature
characteristic was twofold higher than over the suboptimal domain from 17
to 30 degrees C. The macromolecular composition of exponentially growing
cells was invariant over the entire range from 0 to 30 degrees C.
Variations of temperature and growth rate were independently investigated
through chemostat experiments in order to characterize their respective
effects on cell macromolecular composition and size. The effect of growth
rate in this psychrotrophic strain is identical to that of all other
bacteria assayed so far. In contrast, an original biphasic variation of
total protein concentration was demonstrated in strain MF0 with respect to
temperature, with a maximum at 17 to 20 degrees C. Indeed, increasing the
temperature in the chemostat resulted in a biphasic decrease in the net
protein production rate: a very slight decrease below 17 degrees C and a
much larger decrease from 17 to 28 degrees C. These results could signify
an increase in the cellular protein degradation rate with increasing
temperature, especially above 17 degrees C.
Copyright © 1996, American Society for Microbiology
Evidence for two domains of growth temperature for the psychrotrophic bacterium Pseudomonas fluorescens MF0
Laboratoire de Microbiologie du Froid, Evreux, France.
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