ISSN:
1432-072X
Keywords:
Respiration
;
Molar growth yields
;
Thermophile
;
Energy conservation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Whole cells of the extreme thermophile Thermus thermophilus HB8 contained a membrane-bound respiratory chain (comprised of nicotinamide nucleotide transhydrogenase, NADH dehydrogenase, menaquinone, and cytochromes b, c, aa3, o), which exhibited a maximum→H+/O quotient of approximately 8 g-ion H+·g-atom O-1 for the oxidation of endogenous substrates. Whole cell respiration at 70° at the expense of endogenous substrates or ascorbate-TMPD generated a transmembrane protonmotive force (Δp) of up to 197 mV and an intracellular phosphorylation poteintial (ΔGp), measured under similar conditions, of approximately 43.9 kJ·mol-1. The measured ΔGp/Δp ratio thus indicated an→H+/ATP quotient of approximately 2.3 g-ion H+·mole ATP-1. Glucose-limited continuous cultures of T. thermophilus at 60°, 70° and 78.5° exhibited extremely low moler growth yields (Y O2 max ≤27.6 g cells·mol O 2 -1 ; Y glucose max ≤64.4 g cells ·mol glucose-1) compared with mesophilic bacteria of similar respiratory chain composition and proton translocation efficiency. These low yields are probably at least partly explained by the extremely high permeability of the cytoplasmic membrane to H+, which thus causes the cells to respire rapidly in order to maintain the protonmotive force at a level commensurate with cell growth.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00451497
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