THE RESPIRATORY CHAIN AND BIOENERGETICS IN ALKALOPHILIC BACTERIA (BACILLUS, FIRMUS, ALCALOPHILUS).
Item
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Title
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THE RESPIRATORY CHAIN AND BIOENERGETICS IN ALKALOPHILIC BACTERIA (BACILLUS, FIRMUS, ALCALOPHILUS).
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Identifier
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AAI8312357
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identifier
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8312357
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Creator
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LEWIS, RICHARD JAY.
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Contributor
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Terry Ann Krulwich | Ruth Abramson
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Date
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1983
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biophysics, General
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Abstract
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Bacillus firmus RAB and Bacillus alcalophilus grow optimally at pH 10.5-11.0. Certain bioenergetic problems that are also found in other organisms are thus exaggerated in these obligate alkalophiles. Maintaining an acidic cytoplasmic pH relative to the external milieu is accomplished through electrogenic Na('+)/H('+) antiport whose operation is one of the peculiar energy demands of alkalophiles. In addition, the energy requirement for ATP synthesis is somewhat greater due to a higher (DELTA)G(DEGREES) at elevated pH's.;Difference spectroscopy revealed extraordinary levels of a-, b- and c-type cytochromes in alkalophile membranes (> 5 nmol heme/mg protein). Non-alkalophilic mutants derived from the alkalophiles had greatly reduced quantities of membrane cytochromes (< 2 nmol heme/mg protein). Redox potentiometry revealed an abundance of different cytochrome species in the alkalophiles. Cytochromes from B. alcalophilus vesicles prepared at pH 9.0 (typical cytoplasmic pH of whole cells) had the following midpoint potentials: cytochromes a and a(,3), +240 mV; cytochrome b's, +20, -120, -240 and -320 mV; cytochrome c, +70 mV. One a-type cytochrome and at least one b-type cytochrome exhibited pH-dependent midpoint potentials. Alkalophile vesicles contained an unusually low potential Reiske FeS (EPR signal g = 1.90) protein. A cytochrome a, Em(,7) + 100 mV, one cytochrome b, Em(,7) -120 mV and a cytochrome c Em(,7) +140 mV were identified in the non-alkalophilic mutant. No Rieske protein was distinguished. Analogous results were obtained in B. firmus RAB and its non-alkalophilic mutant. Both alkalophiles have high molar growth yields (Ymal (TURN)40 g dry weight/mole malate consumed) and conventional oxygen utilization rates. The above data raised the possibility that special properties of the alkalophile respiratory chain make them particularly efficient in energy transduction; this possibility was supported by H('+)/O determinations at alkaline but not neutral pH. A very rapid initial phase of respiration-linked proton ejection by cells of B. firmus RAB at pH 9.0 had a stoichiometry of at least 9. No such fast phase was seen at H 7.0 or in the non-alkalophilic mutant, whose H('+)/O stoichiometry was approximately 4. Furthermore, growth yields for non-alkalophilic derivatives of both species were much lower (Ymal (TURN)20) than those of the wild type parents. The results indicated that the function of respiratory chains of the mutants are severely compromised. This is also true of the wild type respiratory chain operating at neutral pH and may be related to the inability of alkalophiles to grow at pH 7.0.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biomedical Sciences
