ISSN:
1432-072X
Keywords:
Molar growth yields
;
Thermoacidophile
;
Respiratory chain energy conservation
;
Membrane permeability
;
Temperature and pH
;
Bacillus acidocaldarius
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The molar yield coefficients (Y glucose, Y O 2) of glucose-limited continuous cultures of the thermoacidophile Bacillus acidocaldarius have been measured as a function of dilution rate as well as over a range of temperature and pH (51°C to 64°C, pH 2.8–5.5) at a fixed dilution rate of approximately 0.1 h-1. The highest growth yields were observed at 51°C and pH〉4.3 (Y glucose 54.8 g cells · mol glucose-1, Y O 2 15.0 g cells · mol O 2 -1 ), but were very much lower than those of mesophilic neutrophiles of similar respiratory chain composition to B. acidocaldarius. Even lower growth yields were observed when the temperature was raised or when the pH was lowered, lowest yields occurring at 64°C and pH 2.8 (Y glucose 23.4 g cells · mol glucose-1, Y O 2 5.9 g cells · mol O 2 -1 ). These decreases in growth yield could be correlated with increases in the permeability of the cytoplasmic membrane to protons, i.e. cells needed to catalyse enhanced rates of substrate oxidation in order to avoid a potentially lethal acidification of the cytoplasm. This strategy appears to be successful in that the specific death rates in situ were very low for all cultures except those growing under the most extreme conditions (64°C, pH 2.8).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00413481
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