Keeping a neutral cytoplasm; the bioenergetics of obligate acidophiles

Matin, Abdul

doi:10.1111/j.1574-6968.1990.tb04104.x

Cited by 40 publications

(19 citation statements)

References 36 publications

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“…The activity of sugar uptake in the presence of DNP below 500 pM either indicates that the cell is resistant to the effects of DNP, or that a pH gradient is maintained despite permeabilization of the membrane with transport continuing to operate with an inside-positive Ary. The complete loss of activity at 1 mM DNP could be due to non-specific effects on the cell and/or cell membrane as described in previous studies (Matin, 1990b). However, if non-specific effects are responsible they would affect all systems equally and this did not happen as only partial inhibition of high-affinity maltose transport (50-60 YO) occurred.…”

Section: Sugar Transport Experimentsmentioning

confidence: 58%

“…This positive dry balances the influx of H+ ions and maintains cytoplasmic pH as well as the pH gradient, even in non-viable cells. A similar effect is thought to occur in the presence of protonophores (Matin, 1990b;Bakker, 1990). As H+ conductance of the cell membrane is increased with addition of the protonophore so the Ary becomes insidepositive and limits the influx of HS ions.…”

Section: Sugar Transport Experimentsmentioning

confidence: 80%

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Nutrient utilization and transport in the thermoacidophilic archaeon Sulfolobus shibatae

Yallop

Charalambous

1996

Microbiology

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Growth of the thermoacidophilic archaeon Sulfolobus shibatae was tested on a range of carbon and nitrogen sources. Optimal defined and complex growth media were developed and growth conditions in both shake flask and fermenter cultures were optimized. Better growth was observed on maltose in particular and disaccharides in general than on monosaccharides. Moreover, maltose utilization was not repressed in the presence of glucose which suggests that glucose is not the preferred substrate of S. shibatae. Uptake studies putatively identified two saturable, constitutive maltose transport systems, a high-aff inity, possible membrane-binding system with a Km of 20 pM and a V-of 218 nmol min-l (mg protein)-l, and a low-aff inity, protondependent system with a Km of 158 pM and a VmuI of 680 nmol min-l (mg protein)-l. Both systems showed differential responses to treatment with 2,4 dinitrophenol and arsenate, and differed from other maltose transport mechanisms described in being constitutive under all conditions tested and not repressed by glucose.

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Section: Sugar Transport Experimentsmentioning

confidence: 58%

Section: Sugar Transport Experimentsmentioning

confidence: 80%

Nutrient utilization and transport in the thermoacidophilic archaeon Sulfolobus shibatae

Yallop

Charalambous

1996

Microbiology

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“…The obligately acidophilic organism T. ferrooxidans has an internal pH of about 6.5, and when cells are growing on Fe 2ϩ at pH 2.0, they maintain a ⌬pH of 4.5 U (7). Unlike other bacteria, acidophilic bacteria with a large ⌬pH have a positive inside membrane potential rather than a negative inside membrane potential, which subtracts from the H ϩ gradient instead of augmenting it (16). Nevertheless, in spite of the fact that it originated from a bacterium that has a positive inside membrane potential, the T. ferrooxidans ArsB arsenite efflux pump membrane was functional in E. coli.…”

Section: Discussionmentioning

confidence: 99%

The Chromosomal Arsenic Resistance Genes of Thiobacillus ferrooxidans Have an Unusual Arrangement and Confer Increased Arsenic and Antimony Resistance to Escherichia coli

Butcher

Deane

Rawlings

2000

Appl Environ Microbiol

182

115

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The chromosomal arsenic resistance genes of the acidophilic, chemolithoautotrophic, biomining bacterium Thiobacillus ferrooxidans were cloned and sequenced. Homologues of four arsenic resistance genes, arsB, arsC, arsH, and a putative arsR gene, were identified. The T. ferrooxidans arsB (arsenite export) and arsC (arsenate reductase) gene products were functional when they were cloned in an Escherichia coli ars deletion mutant and conferred increased resistance to arsenite, arsenate, and antimony. Therefore, despite the fact that the ars genes originated from an obligately acidophilic bacterium, they were functional in E. coli. Although T. ferrooxidans is gram negative, its ArsC was more closely related to the ArsC molecules of gram-positive bacteria. Furthermore, a functional trxA (thioredoxin) gene was required for ArsC-mediated arsenate resistance in E. coli; this finding confirmed the gram-positive ArsC-like status of this resistance and indicated that the division of ArsC molecules based on Gram staining results is artificial. Although arsH was expressed in an E. coli-derived in vitro transcription-translation system, ArsH was not required for and did not enhance arsenic resistance in E. coli. The T. ferrooxidans ars genes were arranged in an unusual manner, and the putative arsR and arsC genes and the arsBH genes were translated in opposite directions. This divergent orientation was conserved in the four T. ferrooxidans strains investigated.Thiobacillus ferrooxidans is an acidophilic (optimum pH, 1.8 to 2.5), obligately chemolithotrophic bacterium that obtains its energy through oxidation of ferrous iron to ferric iron or oxidation of reduced inorganic sulfur compounds to sulfuric acid. It is a member of a consortium of bacteria (which includes Thiobacillus caldus and Leptospirillum ferrooxidans) that is used in commercial biooxidation processes to recover gold from arsenopyrite ores (22). Although recent analysis of microbial populations in continuous-flow biooxidation tanks has revealed that T. ferrooxidans may not be as dominant as was once thought, this organism is nevertheless usually present in such tanks (21). Total arsenic levels greater than 13 g liter Ϫ1 may be present in arsenopyrite biooxidation tanks, and therefore the microorganisms present must have a mechanism of resistance to arsenic (8).Plasmid-associated arsenic efflux resistance mechanisms have been known for many years and have been extensively reviewed (5,23,(30)(31)(32)35). Although the number of components of these systems varies, in the case of Escherichia coli plasmids R773 and R46, as well as Acidiphilium multivorum plasmid pKW301 (34), as many as five genes (arsRDABC) are present. In the case of R773, the genes are transcribed in a single operon. The arsR and arsD genes encode repressors that control the basal and upper levels of ars operon expression, while the arsABC genes encode the structural components of the arsenic resistance mechanism. ArsA is an ATPase which forms a complex with ArsB, the transmembrane arsenite efflux p...

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“…Microorganisms that thrive in acidic environments are uniquely characterized by the ability to conserve energy through cellular processes that maintain a high transmem-brane pH (⌬pH) gradient (8,11,22,23,28). Extracytoplasmic oxidation of sulfur and metal sulfides has been linked to the generation of energy through chemiosmotic coupling in chemolithotrophic acidophiles (8).…”

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confidence: 99%

Bioenergetic Response of the Extreme Thermoacidophile Metallosphaera sedula to Thermal and Nutritional Stresses

Peeples¹,

Kelly

1995

Appl Environ Microbiol

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The bioenergetic response of the extremely thermoacidophilic archaeon Metallosphaera sedula to thermal and nutritional stresses was examined. Continuous cultures (pH 2.0, 70؇C, and dilution rate of 0.05 h ؊1) in which the levels of Casamino Acids and ferrous iron in growth media were reduced by a step change of 25 to 50% resulted in higher levels of several proteins, including a 62-kDa protein immunologically related to the molecular chaperone designated thermophilic factor 55 in Sulfolobus shibatae (J. D. Trent, J. Osipiuk, and T. Pinkau, J. Bacteriol. 172:1478-1484, 1990), on sodium dodecyl sulfate-polyacrylamide gels. The 62-kDa protein was also noted at elevated levels in cells that had been shifted from 70 to either 80 or 85؇C. The proton motive force (⌬p), transmembrane pH (⌬pH), and membrane potential (⌬) were determined for samples obtained from continuous cultures (pH 2.0, 70؇C, and dilution rate of 0.05 h ؊1) and incubated under nutritionally and/or thermally stressed and unstressed conditions. At 70؇C under optimal growth conditions, M. sedula was typically found to have a ⌬p of approximately ؊190 to ؊200 mV, the result of an intracellular pH of 5.4 (extracellular pH, 2.0) and a ⌬ of ؉40 to ؉50 mV (positive inside). After cells had been shifted to either 80 or 85؇C, ⌬ decreased to nearly 0 mV and internal pH approached 4.0 within 4 h of the shift; respiratory activity, as evidenced by iron speciation in parallel temperature-shifted cultures on iron pyrite, had ceased by this point. If cultures shifted from 70 to 80؇C were shifted back to 70؇C after 4 h, cells were able to regain pyrite oxidation capacity and internal pH increased to nearly normal levels after 13 h. However, ⌬ remained close to 0 mV, possibly the result of enhanced ionic exchange with media upon thermal damage to cell membranes. Further, when M. sedula was subjected to an intermediate temperature shift from 73 to 79؇C, an increase in pyrite dissolution (ferric iron levels doubled) over that of the unshifted control at 73؇C was noted. The improvement in leaching was attributed to the synergistic effect of chemical and biological factors. As such, periodic exposure to higher temperatures, followed by a suitable recovery period, may provide a basis for improving bioleaching rates of acidophilic chemolithotrophs.

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Keeping a neutral cytoplasm; the bioenergetics of obligate acidophiles

Cited by 40 publications

References 36 publications

Nutrient utilization and transport in the thermoacidophilic archaeon Sulfolobus shibatae

Nutrient utilization and transport in the thermoacidophilic archaeon Sulfolobus shibatae

The Chromosomal Arsenic Resistance Genes of Thiobacillus ferrooxidans Have an Unusual Arrangement and Confer Increased Arsenic and Antimony Resistance to Escherichia coli

Bioenergetic Response of the Extreme Thermoacidophile Metallosphaera sedula to Thermal and Nutritional Stresses

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