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  • 1
    Electronic Resource
    Electronic Resource
    Alkali production by oral bacteria and protection against dental caries (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 193 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: pH is a key environmental factor affecting the physiology, ecology and pathogenicity of the oral biofilms colonizing the hard tissues of the human mouth. Much attention has been focused on the production of organic acids through the metabolism of carbohydrates by pathogenic oral bacteria. Now, evidence is emerging that alkali generation, particularly through ammonia production from arginine and urea, plays major roles in pH homeostasis in oral biofilms and may moderate initiation and progression of dental caries. This short review highlights recent progress on understanding molecular genetic and physiologic aspects of ammonia generation by prominent oral bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09393.x
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  • 2
    Electronic Resource
    Electronic Resource
    Fluoride and organic weak acids as modulators of microbial physiology (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 26 (2003), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fluoride is widely used as an anticaries agent in drinking water and a variety of other vehicles. This use has resulted in major health benefits. However, there are still open questions regarding the mechanisms of anticaries action and the importance of antimicrobial effects in caries reduction. Fluoride acts in multiple ways to affect the metabolism of cariogenic and other bacteria in the mouth. F−/HF can bind directly to many enzymes, for example, heme-containing enzymes or other metalloenzymes, to modulate metabolism. Fluoride is able also to form complexes with metals such as aluminum or beryllium, and the complexes, notably AlF4− and BeF3−·H2O, can mimic phosphate with either positive or negative effects on a variety of enzymes and regulatory phosphatases. The fluoride action that appears to be most important for glycolytic inhibition at low pH in dental plaque bacteria derives from its weak-acid properties (pKa=3.15) and the capacity of HF to act as a transmembrane proton conductor. Since many of the actions of fluoride are related to its weak-acid character, it is reasonable to compare fluoride action to those of organic weak acids, including metabolic acids, food preservatives, non-steroidal anti-inflammatory agents and fatty acids, all of which act to de-energize the cell membrane by discharging ΔpH. Moreover, with the realization that the biofilm state is the common lifestyle for most microorganisms in nature, there is need to consider interactions of fluoride and organic weak acids with biofilm communities. Hopefully, this review will stimulate interest in the antimicrobial effects of fluoride or other weak acids and lead to more effective use of the agents for disease control and other applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.2003.tb00627.x
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  • 3
    Electronic Resource
    Electronic Resource
    Mineralization and responses of bacterial spores to heat and oxidative agents (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 14 (1994), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Mineralization of bacterial spores with Ca2+ and a variety of other mineral cations enhances resistance to heat damage. Part of the enhancement is associated with increased dehydration of the mineralized protoplast or spore core, while part is independent of dehydration and effective for resistance even to dry heat. Spore mineralization was found also to enhance resistance to oxidative damage caused by agents such as tertiary butyl hydroperoxide or H202. In contrast, mineral cations in the environment increased oxidative damage, presumably by catalyzing radical formation. Metal ion chelators such as o-phenanthroline protected spores against such damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.1994.tb00111.x
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  • 4
    Electronic Resource
    Electronic Resource
    Quasi-irreversible inhibition of enolase of Streptococcus mutans by flouride (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 119 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Fluoride at concentrations greater than 0.01 mM was found to be a quasi-irreversible inhibitor of enolase of permeabilized cells of Streptococcus mutans GS-5 and also of isolated yeast enolase. The inhibition appeared to be of the type that has been described for P-ATPases, but was not dependent on added Al3+ or Be2+ ions. Fluoride inhibition of enolase was not reversed by repeatedly washing the permeabilized cells in chilled fluoride-free medium but could be reversed by the product, phosphoenolpyruvate, or by very high levels of the substrate, 2-phosphoglycerate. Irreversible inhibition of glycolysis was not evident after fluoride treatment of intact cells, washing to remove unbound or loosely bound fluoride and addition of glucose, presumably because intracellular levels of phosphoenolpyruvate were sufficiently high to preclude irreversible fluoride inhibition of enolase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb06902.x
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  • 5
    Electronic Resource
    Electronic Resource
    Acid adaptation in Streptococcus mutans UA159 alleviates sensitization to environmental stress due to RecA deficiency (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 126 (1995), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A RecA-deficient stain of Streptococcus mutans, isolated previously, was found to be more susceptible than the prototroph organism to acid killing and also showed reduced colony-forming ability on sucrose-containing medium. The deficient strain was able to grow in chemostat culture at a low pH value of 5 and did not show reduced capacity to produce acid in standard pH-drop experiments with excess glucose. Moreover, it was able to undergo an adaptive response when grown at a low pH to become more resistant to acid killing and also to killing by ultraviolet radiation or hydrogen peroxide. In fact, after adaptation, it was nearly as resistant as the prototroph strain. These findings were interpreted, in part, in terms of an acid-inducible DNA repair system which functions independently of RecA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1995.tb07427.x
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  • 6
    Electronic Resource
    Electronic Resource
    Hydroperoxide inactivation of enzymes within spores of Bacillus megaterium ATCC19213 (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 142 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Hydroperoxide inactivation of the protoplast enzymes enolase, aldolase and glucose-6-phosphate dehydrogenase in intact spores of Bacillus megaterium ATCC19213 was assessed by first treating the cells with lethal levels of H2O2, then germinating them in the presence of chloramphenicol prior to permeabilization and enzyme assays. Glucose-6-phosphate dehydrogenase proved to be more sensitive to H2O2than enolase or aldolase, in agreement with findings for isolated enzymes. Average D values (time for 90% inactivation) for spores treated with 0.50% H2O2 were 173 min for enolase, 67 min for aldolase and 32 min for glucose-6-phosphate dehydrogenase, compared with a D value of 34 min for spore killing. H2O2 killing of spores was found to be conditional in that recoveries of survivors were greater on complex medium than on minimal medium. Overall, it appeared that oxidative inactivation of enzymes may be important for hydroperoxide killing of spores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08444.x
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  • 7
    Electronic Resource
    Electronic Resource
    Sporicidal activity of tertiary butyl hydroperoxide (1994)
    Springer
    Archives of microbiology 161 (1994), S. 184-190 
    Details
    ISSN: 1432-072X
    Keywords: Organic hydroperoxides ; Bacterial spores ; Oxidative killing ; Antioxidants ; Minerals ; Bacillus megaterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tertiary butyl hydroperoxide (t-BOOH) was found to be sporicidal for Bacillus megaterium ATCC19213. Sporicidal action was very temperature dependent, and the potency of t-BOOH increased about tenfold for each increase in temperature of 15 °C over the range from 30° to 70 °C. At still higher temperatures, heat and μmolar levels of t-BOOH were mutually potentiating for killing. Vegetative cells and germinated spores were some thousand times less resistant to t-BOOH than dormant spores. The order of resistance for spores was: Bacillus stearothermophilus ATCC7953 〉 Bacillus subtilis var. niger = Bacillus megaterium ATCC33729 〉 Bacillus megaterium ATCC19213. Killing was not enhanced by decoating and occurred without germination or loss of refractility of the spores. Spore resistance to t-BOOH was lower at more acid pH values and was decreased also by demineralization. Spores could be protected by the chelator o-phenanthroline, especially in association with Fe2+. Overall, it seemed that killing was associated with nonmetabolic formation of alkyl peroxyl radicals, which are thought to be responsible for killing of vegetative cells by organic hydroperoxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276481
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  • 8
    Electronic Resource
    Electronic Resource
    Inhibition of proton-translocating ATPases of Streptococcus mutans and Lactobacillus casei by fluoride and aluminum (1990)
    Springer
    Archives of microbiology 155 (1990), S. 22-27 
    Details
    ISSN: 1432-072X
    Keywords: Fluoride ; Aluminum ; F1F0 ATPase ; Oral bacteria ; Streptococcus mutans ; Lactobacillus casei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One of the major effects of fluoride on oral bacteria is a reduction in acid tolerance, and presumably also in cariogenicity. The reduction appears to involve transport of protons across the cell membrane by the weak acid HF to dissipate the pH gradient, and also direct inhibition of the F1F0, proton-translocating ATPases of the organisms, especially for Streptococcus mutans. This direct inhibition by fluoride was found to be dependent on aluminum. The dependence on aluminum was indicated by the protection against fluoride inhibition afforded by the Al-chelator deferoxamine and by loss of protection after addition of umolar levels of Al3+, which were not inhibitory for the enzyme in the absence of fluoride. The F1 form of the enzyme dissociated from the cell membrane previously had been found to be resistant to fluoride in comparison with the F1F0 membrane-associated form. However, this difference appeared to depend on less aluminum in the F1 preparation in that the sensitivity of the F1 enzyme to fluoride could be increased by addition of umolar levels of Al3+. The effects of Al on fluoride inhibition were apparent when enzyme activity was assayed in terms of phosphate release from ATP or with an ATP-regenerating system containing phosphoenolpyruvate, pyruvate kinase, NADH and lactic dehydrogenase. Also, Be2+ but not other metal cations, e.g. Co2+, Fe2+, Fe3+, Mn2, Sn2+, and Zn2+, served to sensitize the enzyme to fluoride inhibition. The differences in sensitivities of enzymes isolated from various oral bacteria found previously appeared also to be related to differences in levels of Al. Even the fluoride-resistant enzyme of isolated membranes of Lactobacillus casei ATCC 4646 could be rendered fluoride-sensitive through addition of Al3+. Thus, the F1F0 ATPases of oral bacteria were similar to E1E2 ATPases of eukaryotes in being inhibited by Al-F complexes, and the inhibition presumably involved formation of ADP-Al-F inf3 sup- complexes during catalysis at the active sites of the enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291269
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  • 9
    Electronic Resource
    Electronic Resource
    Sporicidal activity of tertiary butyl hydroperoxide (1994)
    Springer
    Archives of microbiology 161 (1994), S. 184-190 
    Details
    ISSN: 1432-072X
    Keywords: Key words: Organic hydroperoxides – Bacterial spores – Oxidative killing – Antioxidants – Minerals –Bacillus megaterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Tertiary butyl hydroperoxide (t-BOOH) was found to be sporicidal for Bacillus megaterium ATCC19213. Sporicidal action was very temperature dependent, and the potency of t-BOOH increased about tenfold for each increase in temperature of 15 °C over the range from 30° to 70 °C. At still higher temperatures, heat and µmolar levels of t-BOOH were mutually potentiating for killing. Vegetative cells and germinated spores were some thousand times less resistant to t-BOOH than dormant spores. The order of resistance for spores was: Bacillus stearothermophilus ATCC7953〉Bacillus subtilis var. niger=Bacillus megaterium ATCC33729〉Bacillus megaterium ATCC19213. Killing was not enhanced by decoating and occurred without germination or loss of refractility of the spores. Spore resistance to t-BOOH was lower at more acid pH values and was decreased also by demineralization. Spores could be protected by the chelator o-phenanthroline, especially in association with Fe2+. Overall, it seemed that killing was associated with nonmetabolic formation of alkyl peroxyl radicals, which are thought to be responsible for killing of vegetative cells by organic hydroperoxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276481
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  • 10
    Electronic Resource
    Electronic Resource
    Magnesium and calcium ions enhance barotolerance of streptococci (1971)
    Springer
    Archives of microbiology 79 (1971), S. 80-92 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Magnesium and calcium ions were found to enhance barotolerance of Streptococcus faecalis ATCC strain 9790 growing in a complex, glucose-containing medium. Enhancement was indicated both by higher growth rates and yields at 408 atm, and also by an increase in the maximum pressure permitting growth from 550 to 700 atm. The optimum concentration of either ion was ca. 50 mM, and both ions appeared to be equipotent in affecting the same processes by chemically specific interactions. Sodium, potassium, strontium, manganous, chloride, bromide or sulfate ions were all ineffective or only marginally effective in enhancing barotolerance. Mg++ and Ca++ also enhanced growth of compressed, ribose-degrading cultures. Pressure increased the sensitivity of streptococcal growth to low pH, and there appeared to be two distinct effects of Mg++ and Ca++ on barotolerance. First, the rate of exponential growth was enhanced prior to the time at which culture acidity began to limit growth. Second, growth was possible in more acid conditions under pressure when the ions were present, and enhanced yields from compressed cultures were related to this partial reversal of the potentiating effect of high pressure on acid inhibition of growth. Barotolerance of Escherichia coli or Saccharomyces cerevisiae was not enhanced by these ions; while tolerance of two types of chain-forming cocci freshly isolated from a rotting mussel was enhanced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00412043
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