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1.
The ultrastructure of cells of Acidiphilium rubrum, which is an acidophilic aerobic photosynthetic bacterium containing zinc-complexed bacteriochlorophyll a, was studied by electron microscopy with the rapid substitution technique. Thin-section electron microscopy indicated that
any type of internal photosynthetic membranes was not present in this organism despite a relatively high content of the photopigment.
The majority of cells had poly-β-hydroxybutyrate granules and electron-dense spherical bodies identified as being polyphosphate
granules. When the organism was grown chemotrophically with 0.1% FeSO4, it produced another group of electron-dense granules that were associated with the inner part of the cytoplasmic membrane.
An energy-dispersive X-ray analysis showed that these membrane-bound, electron-dense granules contained iron.
Received: 24 November 1999 / Accepted: 5 January 2000 相似文献
2.
Poly-beta-hydroxybutyrate Utilization by Soybean (Glycine max Merr.) Nodules and Assessment of Its Role in Maintenance of Nitrogenase Activity 总被引:1,自引:0,他引:1
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Soybean (Glycine max) nodule bacteroids contain high concentrations of poly-β-hydroxybutyrate and possess a depolymerase system that catalyzes the hydrolysis of the polymer. Changes in poly-β-hydroxybutyrate content and in activities of nitrogenase, β-hydroxybutyrate dehydrogenase, and isocitrate lyase in nodule bacteroids were investigated under conditions in which the supply of carbohydrate from the soybean plants was interrupted. The poly-β-hydroxybutyrate content of bacteroids did not decrease appreciably until the carbohydrate supply from the host plants was limited by incubation of excised nodules, incubation of plants in the dark, or by senescence of the host plant. Isocitrate lyase activity in bacteroids was not detected until poly-β-hydroxybutyrate utilization appeared to begin. The presence of a supply of poly-β-hydroxybutyrate in nodule bacteroids was not sufficient for maintenance of high nitrogenase activity under conditions of limited carbohydrate supply from the host plant. An unusually high activity of β-hydroxybutyrate dehydrogenase was observed in bacteroid extracts but no significant change in the activity of this enzyme was observed as a result of apparent utilization of poly-β-hydroxybutyrate by nodule bacteroids. 相似文献
3.
Induction of Encystment and Poly-β-Hydroxybutyric Acid Production by Azotobacter chroococcum MAL-201
Azotobacter chroococcum MAL-201, when grown under nitrogen-free conditions with excess glucose, accumulated poly-β-hydroxybutyric acid amounting
to 75% of cell dry weight at the late exponential phase. This led to induction of encystment, which increased steadily with
concomitant intracellular degradation of the polymer. Increase in encystment and PHB production were parallel up to 0.5% (wt/vol)
glucose. Further increase in glucose reduced cyst formation but enhanced PHB accumulation. Replacement of glucose by n-butyl alcohol and metabolically related compounds identified crotonate as the best encystment inducer followed by β-hydroxybutyrate
and butyrate, but PHB production was inhibited in general. Supplementation of medium with these compounds enhanced the onset
of encystment, and only β-hydroxybutyrate increased PHB accumulation significantly.
Received: 23 April 1997 / Accepted: 31 May 1997 相似文献
4.
Bruce H. Bleakley Murray H. Gaskins David H. Hubbell Stephan G. Zam 《Applied microbiology》1988,54(12):2986-2995
Azospirillum lipoferum RG6xx was grown under conditions similar to those resulting in encystment of Azotobacter spp. A. lipoferum produced cells of uniform shape when grown on nitrogen-free β-hydroxybutyrate agar. Cells accumulated poly-β-hydroxybutyrate and often grew as chains or filaments that eventually lost motility and formed capsules. Within 1 week, vegetative A. lipoferum inocula were converted into microflocs arising from filaments or chains. Cells within microflocs were pleomorphic, contained much poly-β-hydroxybutyrate, and were encapsulated. Some cells had a cystlike morphology. Up to 57% of the dry weight of encapsulated flocs was poly-β-hydroxybutyrate, whereas vegetative cells grown in broth with combined nitrogen had only 3% of their dry weight as poly-β-hydroxybutyrate. Neither encapsulated cells in flocs nor nonencapsulated vegetative cells were significantly desiccation resistant. Under starvation conditions (9 days) only 25% of encapsulated cells remained viable, whereas vegetative cells multiplied severalfold. In short-term germination experiments with encapsulated flocs, nitrate, ammonium, and soil extract promoted formation of motile vegetative cells. Most cells in treatments lacking combined nitrogen eventually depleted their visible poly-β-hydroxybutyrate reserves without germinating. The remaining cells retained the reserve polymer and underwent size reduction. 相似文献
5.
Vargas-García MC López MJ Elorrieta MA Suárez F Moreno J 《Journal of industrial microbiology & biotechnology》2002,29(3):129-133
The relationship between exopolysaccharide (EPS) production by Azotobacter vinelandii ATCC 12837 from 4-hydroxybenzoic acid as sole carbon source and other physiological parameters was investigated. In relation
to growth, Azotobacter needed more time in 4-hydroxybenzoic acid to reach levels of biomass similar to those obtained when sugars were used, although
the phenolic compound led to a more extensive exponential phase. The encystment process was initiated after cells had grown
for 24 h, in which small amounts of EPS were synthesized and poly-β-hydroxybutyrate (PHB) accumulation began. Both polymers,
EPS and PHB, showed a similar evolution with time, as well as the formation of cysts, which points out the existence of a
relation between these parameters. This was corroborated by a statistical study, in which significant correlations (P<0.05) were observed when each parameter was compared to the two others. Journal of Industrial Microbiology & Biotechnology (2002) 29, 129–133 doi:10.1038/sj.jim.7000288
Received 01 February 2002/ Accepted in revised form 13 June 2002 相似文献
6.
Gómez MA Rodelas B Sáez F Pozo C Martínez-Toledo MV Hontoria E González-López J 《Applied microbiology and biotechnology》2005,68(5):680-685
Xanthobacter autotrophicus strains with the ability to reduce nitrate and nitrite to either nitrous oxide or molecular nitrogen were isolated from submerged
fixed-film reactors. Isolated strains were Gram-negative rods able to grow on methanol, ethanol and sucrose. The yellow cellular
pigmentation, pleomorphic appearance, and the presence of poly-β-hydroxybutyrate granules suggest that the organisms might
belong to the genus Xanthobacter. Comparison of 16S rDNA gene sequences demonstrated the affiliation of the strains to X. autotrophicus species. The results show that X. autotrophicus may play a role in inorganic nitrogen removal from a denitrifying submerged filter used for the treatment of contaminated
groundwater. To our knowledge, no data on denitrifying activity in X. autotrophicus strains have been reported previously. 相似文献
7.
Esther Imperlini Carmelina Bianco Enza Lonardo Serena Camerini Michele Cermola Giancarlo Moschetti Roberto Defez 《Applied microbiology and biotechnology》2009,83(4):727-738
We evaluated the effects of the main auxin phytohormone, indole-3-acetic acid (IAA), on the central metabolism of Sinorhizobium meliloti 1021. We either treated S. meliloti 1021 wild-type cells with 0.5 mM IAA, 1021+, or use a derivative, RD64, of the same strain harboring an additional pathway
for IAA biosynthesis (converting tryptophan into IAA via indoleacetamide). We assayed the activity of tricarboxylic acid cycle
(TCA) key enzymes and found that activity of citrate synthase and α-ketoglutarate dehydrogenase were increased in both 1021+
and RD64 as compared to the wild-type strain. We also showed that the intracellular acetyl-CoA content was enhanced in both
RD64 and 1021+ strains when compared to the control strain. The activity of key enzymes, utilizing acetyl-CoA for poly-β-hydroxybutyrate
(PHB) biosynthesis, was also induced. The PHB level measured in these cells were significantly higher than that found in control
cells. Moreover, 4-week-long survival experiments showed that 80% of 1021 cells died, whereas 50% of RD64 cells were viable.
Medicago truncatula plants nodulated by RD64 (Mt-RD64) showed an induction of both acetylene reduction activity and stem dry weight production. 相似文献
8.
Enzymes of the Poly-beta-Hydroxybutyrate and Citric Acid Cycles of Rhizobium japonicum Bacteroids
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The activities of several enzymes of the citric acid and poly-β-hydroxybutyrate cycles were measured in Rhizobium japonicum 3I1B-143 bacteroids which had been isolated from soybean nodules by sucrose gradient centrifugation. During the period of developing nitrogenase activity, the specific activity of fumarase, hydroxybutyrate dehydrogenase, β-ketothiolase, and pyruvate dehydrogenase complex increased whereas acetoacetate-succinyl-CoA transferase and isocitrate dehydrogenase decreased. Malate dehydrogenase activity remained constant. The amount of available acetyl-CoA, based on pyruvate dehydrogenase activity, should be sufficient to support both metabolic cycles concurrently. The temporal relationship between nitrogenase activity and poly-β-hydroxybutyrate accumulation has been reexamined. 相似文献
9.
Summary A series of investigations were conducted with the objective of elucidating natural pathways of electron transport from respiratory
processes to the site of N2 fixation in nodule bacteroids. A survey of dehydrogenase activities in a crude extract of soybean nodule bacteroids revealed
relatively high activities of NAD-specific β-hydroxybutyrate and glyceraldehyde-3-phosphate dehydrogenases. Moderate activities
of NADP-specific isocitrate and glucose-6-phosphate dehydrogenases were observed. By use of the ATP-dependent acetylene reduction
reaction catalyzed by soybean bacteroid nitrogenase, and enzymes and cofactors from bacteroids and other sources, the following
sequences of electron transport to bacteroid nitrogenase were demonstrated: (1) H2 to bacteroid nitrogenase in presence of a nitrogenase-free extract ofC. pasteurianum; (2) β-hydroxybutyrate to bacteroid nitrogenase in a reaction containing β-hydroxybutyrate dehydrogenase, NADH dehydrogenase,
NAD and benzyl viologen; (3) β-hydroxybutyrate dehydrogenase, to nitrogenase in reaction containing NADH dehydrogenase, NAD
and either FMN or FAD; (4) light-dependent transfer of electrons from ascorbate to bacteroid nitrogenase in a reaction containing
photosystem I from spinach chloroplasts, 2,6-dichlorophenolindophenol, and either azotoflavin from Azotobacter or non-heme
iron protein from bacteroids; (5) glucose-6-phosphate to bacteroid nitrogenase in a system that included glucose-6-phosphate
dehydrogenase, NADP, NADP-ferredoxin reductase from spinach, azotoflavin from Azotobacter and bacteroid non-heme iron protein.
The electron transport factors, azotoflavin and bacteroid non-heme iron protein, failed to function in the transfer of electrons
from an NADH-generating system to bacteroid nitrogenase. When FMN or FAD were added to systems containing azotoflavin and
bacteroid non-heme iron protein, electrons apparently were transferred to the flavin-nucleotides and then nitrogenase without
involvement of azotoflavin and bacteroid non-heme iron protein.
Evidence is available indicating that nodule bacteroids contain flavoproteins analogous to Azotobacter, azotoflavin, and spinach
ferredoxin-NADP reductase. It is concluded that physiologically important systems involved in transport of electrons from
dehydrogenases to nitrogenase in bacteroids very likely will include relatively specific electron transport proteins such
as bacteroid non-heme iron protein and a flavoprotein from bacteroids that is analogous to azotoflavin. 相似文献
10.
Cold stress resulted in a decrease in the poly-β-hydroxybutyrate (PHB) content of non-cold-acclimated Rhizobium DDSS69 cultures. Analysis of the specific activity of β-ketothiolase and β-hydroxybutyrate dehydrogenase revealed that decrease
in PHB levels was a result of the inhibition of synthesis of PHB rather than an increase in its breakdown. Rhizobium ATR1, a cold-acclimated strain, revealed the presence of a stable PHB metabolism that did not show any significant differences
either in PHB levels or in the activity of enzymes of the PHB metabolism under cold stress, suggesting that PHB is not involved
in cold tolerance. Analysis of specific activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase
of the pentose phosphate pathway showed the upward regulation of alternate pathways of carbohydrate metabolism under cold
stress to rapidly generate energy to overcome the stress. There is diversity in the switching mechanisms of carbon metabolism
among cold-acclimated and non-cold-acclimated Rhizobium isolates. Upward regulation of malate dehydrogenase in both isolates suggests that it is a critical input for cold tolerance.
Received: 26 June 2000 / Accepted: 31 July 2000 相似文献
11.
Rodrigues MF Valentin HE Berger PA Tran M Asrar J Gruys KJ Steinbüchel A 《Applied microbiology and biotechnology》2000,53(4):453-460
Burkholderia sp. accumulates polyhydroxyalkanoates (PHAs) containing 3-hydroxybutyrate and 3-hydroxy-4-pentenoic acid when grown on mineral
media under limited phosphate or nitrogen, and using sucrose or gluconate as a carbon and energy source. Solvent fractionation
and NMR spectroscopic characterization of these polyesters revealed the simultaneous accumulation of two homopolyesters rather
than a co-polyester with random sequence distribution of the monomers [Valentin HE, Berger PA, Gruys KJ, Rodrigues MFA, Steinbüchel
A, Tran M, Asrar J (1999) Macromolecules 32: 7389–7395]. To understand the genetic requirements for such unusual polyester
accumulation, we probed total genomic DNA from Burkholderia sp. by Southern hybridization experiments using phaC-specific probes. These experiments indicated the presence of more than one PHA synthase gene within the genome of Burkholderia sp. However, when total genomic DNA from Burkholderia sp. was used to complement a PHA-negative mutant of Ralstonia eutropha for PHA accumulation, only one PHA synthase gene was obtained resembling the R. eutropha type of PHA synthases, based on amino acid sequence similarity. In addition to the PHA synthase gene, based on high sequence
homology, genes encoding a β-ketothiolase and acetoacetyl-CoA reductase were identified in a gene cluster with the PHA synthase
gene. The arrangement of the three genes is quite similar to the R. eutropha poly-β-hydroxybutyrate biosynthesis operon.
Received: 3 September 1999 / Received revision: 29 October 1999 / Accepted: 5 November 1999 相似文献
12.
13.
Rhizobium meliloti 300hl3 reached the stationary phase of growth very quickly and had an early death when 8.6 μM parathion was added to the
growth medium at the start of the culture. Cells also changed their quantitative composition: total carbohydrate content and
poly-β-hydroxybutyrate accumulation diminished, proteins and phospholipids of cellular membranes increased, and some alterations
in the proportion of membrane fatty acids were noticed. 相似文献
14.
J. S. Potekhina N. G. Sherisheva L. P. Povetkina A. P. Pospelov T. A. Rakitina F. Warnecke G. Gottschalk 《Applied microbiology and biotechnology》1999,51(5):639-646
In acetate-limited chemostat cultures of Acinetobacter johnsonii 210A at a dilution rate of 0.1 h−1 the polyphosphate content of the cells increased from 13% to 24% of the biomass dry weight by glucose (100 mM), which was
only oxidized to gluconic acid. At this dilution rate, only about 17% of the energy from glucose oxidation was calculated
to be used for polyphosphate synthesis, the remaining 83% being used for biomass formation. Suspensions of non-growing, phosphate-deficient
cells had a six- to tenfold increased uptake rate of phosphate and accumulated polyphosphate aerobically up to 53% of the
biomass dry weight when supplied with only orthophosphate and Mg2+. The initial polyphosphate synthesis rate was 98 ± 17 nmol phosphate min−1 mg protein−1. Intracellular poly-β-hydroxybutyrate and lipids served as energy sources for the active uptake of phosphate and its subsequent
sequestration to polyphosphate. The H+-ATPase inhibitor N,N′-dicyclohexylcarbodiimide caused low ATP levels and a severe inhibition of polyphosphate formation, suggesting the involvement
of polyphosphate kinase in polyphosphate synthesis. It is concluded that, in A. johnsonii 210A, (i) polyphosphate is accumulated as the energy supply is in excess of that required for biosynthesis, (ii) not only
intracellular poly-β-hydroxybutyrate but also neutral lipids can serve as an energy source for polyphosphate-kinase-mediated
polyphosphate formation, (iii) phosphate-deficient cells may accumulate as much polyphosphate as activated sludges and recombinants
of Escherichia coli designed for polyphosphate accumulation.
Received: 23 October 1998 / Received revision: 18 January 1999 / Accepted: 22 January 1999 相似文献
15.
The energy charge ofAzotobacter vinelandii was measured and found to be poised at a value of 0.3. This value was expected in view of the rate of oxygen consumption
observed in these resting cells. Adenine nucleotides and poly-β-hydroxybutyric acid were also determined and the relative
amounts of these were used as a basis for speculation on long term survival ofAzotobacter cysts in soil. *** DIRECT SUPPORT *** A01R4012 00003 相似文献
16.
Vecherskaya M Dijkema C Stams AJ 《Journal of industrial microbiology & biotechnology》2001,26(1-2):15-21
Poly-β-hydroxybutyrate (PHB) formation under aerobic conditions via incorporation of [13C-2]acetate as a cosubstrate and its intracellular degradation under anaerobic conditions in a Type II methanotroph was studied
by 13C NMR. During PHB synthesis in the presence of labelled acetate, low levels of β-hydroxybutyrate, butyrate, acetone, isopropanol,
2,3-butanediol and succinate were observed. Subsequent anaerobic PHB breakdown showed enhanced levels of these products at
the expense of PHB. Fermentative metabolism occurring during anaerobic PHB degradation was confirmed in experiments with fully
13C-enriched cells, which were grown on 13C-labelled methane. β-hydroxybutyrate, butyrate, acetate, acetone, isopropanol, 2,3-butanediol and succinate were detected
as multiple 13C-labelled compounds in the culture medium. Our results suggest that intracellular PHB degradation can be used as a reserve
energy source by methanotrophs under anoxic conditions. Journal of Industrial Microbiology & Biotechnology (2001) 26, 15–21. 相似文献
17.
Klucas RV 《Plant physiology》1974,54(4):612-616
Soybean Glycine max. L. Merr. nodule senescence was studied using the loss of acetylene reduction by intact tap root nodules as its indication. Tap root nodules from two varieties (Calland and Beeson) of field-grown soybeans were used. The specific activities of nitrogenase (micromoles/minute gram fresh weight of nodules) as measured by the acetylene reduction assay decreased abruptly between 58 to 65 and 68 to 75 days after planting the Beeson and Calland soybeans, respectively. Major changes were not detected in dry weight, total nitrogen, and leghemoglobin levels during the period when in vivo nitrogenase activity declined. Ammonium levels in the cytosol of nodules and poly-β-hydroxybutyrate increased moderately just prior to or coincidental with the loss of nitrogenase activity. Neither enzymes that have been postulated to be involved in ammonium assimilation nor NADP+-specific isocitrate dehydrogenase exhibited any large changes in specific activities during the initial period when nitrogenase activity declined. 相似文献
18.
Summary When grown with glucose, S. discophorus synthesized large amounts of poly--hydroxybutyrate which accumulated intracellularly as sudanophilic granules. The rate of endogenous oxygen consumption by such cells was markedly increased by Mn++ and even more by Mg++. It has been shown that these inorganic ions stimulate the oxidation of the intracellular poly--hydroxybutyrate.Dedicated by the senior author to Prof. C. B. van Niel on the occasion of his 70th birthday with gratitude for many unforgettable years of association, instruction and stimulation. 相似文献
19.
The intracellular concentration of CoA metabolites and nucleotides was determined in batch cultures of Methylobacterium rhodesianum grown on methanol and shifted to growth on fructose. The intracellular concentration of CoA decreased from a high value of
0.6 nmol/mg poly(β-hydroxybutyrate)-free bacterial dry mass during growth on methanol to a low value of 0.03 nmol/mg poly(β-hydroxybutyrate)-free
bacterial dry mass after a shift to fructose as a carbon source. The levels of NADH, NADPH, and acetyl-CoA were also lower.
Under these conditions, acetyl-CoA was metabolized by both citrate synthase and β-ketothiolase, and poly(β-hydroxybutyrate)
synthesis and growth occurred simultaneously during growth on fructose. Moreover, the level of ATP was approximately 50% lower
during growth on fructose, supporting the hypothesis of a bottleneck in the energy supply during the growth of M. rhodesianum with fructose.
Received: 15 July 1997 / Accepted: 10 November 1997 相似文献
20.
Bradyrhizobium japonicum, the nitrogen-fixing symbiotic partner of soybean, was grown on various carbon substrates and assayed for the presence of
the glyoxylate cycle enzymes, isocitrate lyase and malate synthase. The highest levels of isocitrate lyase [165–170 nmol min–1 (mg protein)–1] were found in cells grown on acetate or β-hydroxybutyrate, intermediate activity was found after growth on pyruvate or galactose,
and very little activity was found in cells grown on arabinose, malate, or glycerol. Malate synthase activity was present
in arabinose- and malate-grown cultures and increased by only 50–80% when cells were grown on acetate. B. japonicum bacteroids, harvested at four different nodule ages, showed very little isocitrate lyase activity, implying that a complete
glyoxylate cycle is not functional during symbiosis. The apparent K
m of isocitrate lyase for d,l-isocitrate was fourfold higher than that of isocitrate dehydrogenase (61.5 and 15.5 μM, respectively) in desalted crude extracts
from acetate-grown B. japonicum. When isocitrate lyase was induced, neither the V
max nor the d,l-isocitrate K
m of isocitrate dehydrogenase changed, implying that isocitrate dehydrogenase is not inhibited by covalent modification to
facilitate operation of the glyoxylate cycle in B. japonicum.
Received: 10 October 1997 / Accepted: 16 January 1998 相似文献