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1.
Activation of heat shock response was observed after an alkaline shift of extracellular pH: it peaked at 5 to 10 min, as was previously reported for the heat-induced response, and was dependent on a functional rpoH gene, which is the positive regulator of the heat shock response. An induction of over sixfold was observed for dnaK and groE. The response was induced by the alkalization of extracellular pH but not by the alkalization of intracellular pH. An acidic shift of extracellular pH failed to activate the heat shock response, showing that the response is specific to the alkaline shift. 相似文献
2.
3.
The metabolism of sulfide, sulfur, and acetate by Beggiatoa alba was investigated under oxic and anoxic conditions. B. alba oxidized acetate to carbon dioxide with the stoichiometric reduction of oxygen to water. In vivo acetate oxidation was suppressed by sulfide and by several classic respiratory inhibitors, including dibromothymoquinone, an inhibitor specific for ubiquinones. B. alba also carried out an oxygen-dependent conversion of sulfide to sulfur, a reaction that was inhibited by several electron transport inhibitors but not by dibromothymoquinone, indicating that the electrons released from sulfide oxidation were shuttled to oxygen without the involvement of ubiquinones. Intracellular sulfur stored by B. alba was not oxidized to sulfate or converted to an external soluble form under aerobic conditions. On the other hand, sulfur stored by filaments of Thiothrix nivea was oxidized to extracellular soluble oxidation products, including sulfate. Sulfur stored by filaments of B. alba, however, was reduced to sulfide under short-term anoxic conditions. This anaerobic reduction of sulfur was linked to the endogenous oxidation of stored carbon and to hydrogen oxidation. 相似文献
4.
Sulfide induction of synthesis of a periplasmic protein in the cyanobacterium Oscillatoria limnetica. 下载免费PDF全文
Two proteins which may play a role in the induction of anoxygenic photosynthesis in Oscillatoria limnetica have been demonstrated by comparing the pattern of labeling during pulses of [35S]methionine of cells incubated under inducing conditions [anaerobic conditions plus 3-(3,4-dichlorophenyl)-1,1-dimethylurea, light, and sulfide) with that of cells incubated under noninducing conditions (without sulfide). The major inducible protein has an apparent molecular mass of 11.5 kilodaltons and is associated with a less strongly labeled 12.5-kilodalton protein. The synthesis of both proteins commences within the first 30 min of induction and continues throughout the 2-h induction period. Since these proteins are not synthesized in the presence of dithionite without sulfide, low redox potential alone is insufficient as an inducer of these proteins. Lysozyme treatment and/or osmotic shock of intact cells results in the release of the sulfide-induced proteins. Our data thus indicate that these proteins are located in the periplasmic space of the cells. 相似文献
5.
Isaksson Axel Philips Anna–Carin Göransson Eva Björkenfeldt Henrik 《Acta veterinaria Scandinavica》1987,28(3-4):455-457
The electrical conductivity (EC) of milk is mainly a function of the electrolyte concentration in the milk and therefore raised in mastitis. The present investigation was aimed at elaborating, if possible, a diagnostic model for screening purposes based on EC determinations and consistent with the diagnostic procedures and interpretations commonly used in laboratory milk diagnosis in the Nordic countries (Klastrup 1975). According to this diagnosis (here called reference diagnosis) cell numbers above 300,000/ml (cell count or the corresponding CMT-score) in foremilk quarter samples during the main part of the lactation period and significantly above the lowest value on within-udder comparison during late lactation are considered indicative of mastitis and bacteriological examinations are made when called for. 相似文献
6.
Yosepha Shahak Christof Klughammer Ulrich Schreiber Etana Padan Inge Herrman Günter Hauska 《Photosynthesis research》1994,39(2):175-181
The reduction by sulfide of exogenous ubiquinone is compared to the reduction of cytochromes in chromatophores of Rhodobacter capsulatus. From titrations with sulfide values for Vmax of 300 and 10 moles reduced/mg bacteriochlorophyll a·h, and for Km of 5 and 3 M were estimated, for decyl-ubiquinone-and cytochrome c-reduction, respectively. Both reactions are sensitive to KCN, as has been found for sulfide-quinone reductase (SQR) in Oscillatoria limnetica, which is a flavoprotein. Effects of inhibitors interfering with quinone binding sites suggest that at least part of the electron transport from sulfide in R. capsulatus employs the cytochrome bc
1-complex via the ubiquinone pool.Abbreviations BChl a
bacteriochlorophyll a
- DAD
diaminodurene
- decyl-UQ
decyl-ubiquinone
- LED
light emitting diode
- NQNO
2-n-nonyl-4-hydroxyquinoline-N-oxide
- PQ-1
plastoquinone 1
- SQR
sulfide-quinone reductase (E.C. 1.8.5.'.)
- UQ
ubiquinone 10
- Qc
the quinone reduction site on the cytochrome b
6
f/bc
1, complex (also termed Qi or Qr or Qn)
- Qs
the quinone reduction site on SQR
- Qz
quinol oxidation site on the b
6
f/bc
1, complex (also termed Qo or Qp) 相似文献
7.
Occurrence of facultative anoxygenic photosynthesis among filamentous and unicellular cyanobacteria. 总被引:7,自引:0,他引:7 下载免费PDF全文
Eleven of 21 cyanobacteria strains examined are capable of facultative anoxygenic photosynthesis, as shown by their ability to photoassimilate CO2 in the presence of Na2S, 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 703-nm light. These include different cyanobacterial types (filamentous and unicellular) of different growth histories (aerobic, anaerobic, and marine and freshwater). Oscillatoria limnetica, Aphanothece halophytica (7418), and Lyngbya (7104) have different optimal concentrations of Na2S permitting CO2 photoassimilation, above which the rate decreases: 3.5, 0.7, and 0.1 mM, respectively. In A. halophytica, for each CO2 molecule photoassimilated two sulfide molecules are oxidized to elemental sulfur, which is excreted from the cells.The ecological and evolutionary significance of anoxygenic photosynthesis in the cyanobacteria is discussed. 相似文献
8.
Induction of anaerobic, photoautotrophic growth in the cyanobacterium Oscillatoria limnetica. 下载免费PDF全文
Anaerobic photoautotrophic growth of the cyanobacterium Oscillatoria limnetica was demonstrated under nitrogen in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (5micron), a constant concentration of Na2S (2.5 mM), and constant pH (7.3). The photoanaerobic growth rate (2 days doubling time) was similar to that obtained under oxygenic photoautotrophic growth conditions. The potential of oxygenic photosynthesis is constitutive in the cells; that of anoxygenic photosynthesis is rapidly (2 h) induced in the presence of Na2S in the light in a process requiring protein synthesis. The facultative anaerobic phototrophic growth physiology exhibited by O. limnetica would seem to represent an intermediate physiological pattern between the obligate anaerobic one of photosynthetic bacteria and the oxygenic one of eucaryotic algae. 相似文献
9.
Overproduction and purification of a functional Na+/H+ antiporter coded by nhaA (ant) from Escherichia coli. 总被引:2,自引:0,他引:2
A Na+/H+ antiporter coded by the nhaA (ant) gene of Escherichia coli has been overproduced and purified. The amino-terminal sequence of the protein has been determined and shown to correlate with initiation at a GUG codon, 75 bases upstream from the previously suggested AUG initiation codon. The purified protein, when reconstituted into proteoliposomes, has Na+/H+ antiport activity. It can mediate sodium uptake when a transmembrane pH gradient is applied. Downhill sodium efflux is shown to be highly dependent on pH and is accelerated by a transmembrane pH gradient. An imposed membrane potential negative inside accelerates Na+ efflux at all pH values tested. These findings suggest that the antiporter is electrogenic both at acid and alkaline pH. The activation at alkaline pH values (2000-fold increase) is consistent with the proposed role of the antiporter in regulation of internal pH at the alkaline pH range. 相似文献
10.
Sulfide inhibition of photosystem II in cyanobacteria (blue-green algae) and tobacco chloroplasts. 总被引:1,自引:0,他引:1
The present study shows that in the presence of 600 nm light, sulfide acts as a specific inhibitor of photosynthetic electron transport between water and Photosystem II in the cyanobacteria Aphanothece halophytica and Synechococcus 6311 as well as in tobacco chloroplasts. In the presence of 600 nm light sulfied affects the fast fluorescence transients as does a low concentration (10 mM) of hydroxylamine; the fluorescence yield decreases in the presence of either chemical and can be restored by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. In chloroplasts, however, NH2OH, an electron donor at high concentrations (40 mM), relieves the sulfide effect. In the dark, sulfide affects the cyanobacterial fluorescence transients through decrease of oxygen tension. The fluorescence yield increases in a similar pattern to that observed under nitrogen flushing. Upon omission of sulfide in A. halophytica, the characteristic aerobic fluorescence transients return, consistent with the ease of alternation between oxygenic and sulfide-dependent anoxygenic photosynthesis in many cyanobacteria. 相似文献