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1.
Nucleotide sequence and biochemical analysis of d-β-hydroxybutyrate dehydrogenase (EC 1.1.1.30), isolated from Rhodobacter sp., indicate functional oligomers composed of subunits of 257 amino acids with a calculated M
r of 26,800 and a pI of 5.90. Compared to mammalian short-chain alcohol dehydrogenases, the bacterial enzyme lacks a C-terminal
lipid anchor domain and was found to be highly active upon expression in Escherichia coli even without lipid supplement. The recombinant enzyme could be highly enriched using a single chromatography step and was
shown to be stable over a broad range of pH and temperature.
Received: 1 April 1999 / Received last revision: 11 June 1999 / Accepted: 11 June 1999 相似文献
2.
Biofilm formation by bacterial cells can be used to modify the subsurface permeability for the purpose of microbial enhanced
oil recovery, bio-barrier formation, and in situ bioremediation. Once injected into the subsurface, the bacteria undergo starvation due to a decrease in nutrient supply and
diffusion limitations in biofilms. To help understand the starvation response of bacteria in biofilms, the relationship between
exopolymer formation and cell culturability was examined in a batch culture. The average cell diameter was observed to decrease
from 0.8 μm to 0.35 μm 3 days after starvation began. Cell chain fragmentation was also observed during starvation. Cells
that underwent starvation in the presence of insoluble exopolymers showed a slower rate of decrease in cell diameter and in
cell chain length than cells without insoluble exopolymers. The rate of decrease in the average cell diameter and cell chain
length were determined using a first order decay model. Cells starved in the presence of exopolymers showed greater culturability
than cells starved without exopolymers. After 200 days starvation, 2.5 × 10−3% cells were culturable, but no increase in cell number was observed. During starvation, the exopolymer concentration remained
constant, an indication that the exopolymer was not consumed by the starving bacteria as an alternative carbon or energy source.
Received: 8 April 1999 / Received revision: 16 July 1999 / Accepted: 6 August 1999 相似文献
3.
A Gram-negative bacterium producing a heat-stable nitrilase highly active on aliphatic dinitriles 总被引:8,自引:0,他引:8
J. E. Gavagan R. DiCosimo A. Eisenberg S. K. Fager P. W. Folsom E. C. Hann K. J. Schneider R. D. Fallon 《Applied microbiology and biotechnology》1999,52(5):654-659
A Gram-negative bacterial strain, identified as Acidovorax facilis strain 72W, has been isolated from soil by enrichment using 2-ethylsuccinonitrile as the sole nitrogen source. This strain
grows on a variety of aliphatic mono- and dinitriles. Experiments using various heating regimes indicate that nitrile hydratase,
amidase and nitrilase activities are present. The nitrilase is efficient at hydrolyzing aliphatic dinitriles to cyanoacid
intermediates. It has a strong bias for C3–C6 dinitriles over mononitriles of the same chain length. Whole, resting cell hydrolysis of 2-methylglutaronitrile results in
4-cyanopentanoic acid and 2-methylglutaric acid as the major products. Heating, at least 20 min at 50 °C, eliminates nitrile
hydratase and amidase activities, resulting in greater than 97% selectivity to 4-cyanopentanoic acid. The nitrilase activity
has good heat stability, showing a half-life of 22.7 h at 50 °C and a temperature optimum of at least 65 °C for activity.
The strain has been deposited as ATCC 55746.
Received: 26 January 1999 / Received revision: 10 June 1999 / Accepted: 27 June 1999 相似文献
4.
We have developed a method for measurement of plasma membrane water permeability (P
f) in intact cells using laser scanning confocal microscopy. The method is based on confocal recording of the fluorescence
intensity emitted by calcein-loaded adherent cells during osmotic shock. P
f is calculated as a function of the time constant in the fluorescence intensity change, the cell surface-to-volume ratio and
the fractional content of the osmotically active cell volume. The method has been applied to the measurement of water permeability
in MDCK cells. The cells behaved as linear osmometers in the interval from 100 to 350 mosM. About 57% of the total cell volume
was found to be osmotically inactive. Water movement across the plasma membrane in intact MDCK cells was highly temperature
dependent. HgCl2 had no effect on water permeability, while amphotericin B and DMSO significantly increased P
f values. The water permeability in MDCK cells transfected with aquaporin 2 was an order of magnitude higher than in the intact
MDCK cell line. The water permeability of the nuclear membrane in both cell lines was found to be unlimited. Thus the intranuclear
fluid belongs to the osmotically active portion of the cell. We conclude that the use of confocal microscopy provides a sensitive
and reproducible method for measurement of water permeability in different types of adherent cells and potentially for coverslip-attached
tissue preparations.
Received: 12 June 1999 / Revised version: 21 February 2000 / Accepted: 25 February 2000 相似文献
5.
Pollutant degradation in biotrickling filters for waste air treatment is generally thought to occur only in the biofilm.
In two experiments with toluene degrading biotrickling filters, we show that suspended microorganisms in the recycle liquid
may substantially contribute to the overall pollutant removal. Two days after reactor start up, the overall toluene elimination
capacity reached a maximum of 125 g m−3 h−1, which was twice that found during prolonged operation. High biodegradation activity in the recycle liquid fully accounted
for this short-term peak of pollutant elimination. During steady-state operation, the toluene degradation in the recycle liquid
was 21% of the overall elimination capacity, although the amount of suspended biomass was only 1% of the amount of immobilized
biomass. The results suggest that biotrickling filter performance may be improved by selecting operating conditions allowing
for the development of an actively growing suspended culture.
Received: 16 June 1999 / Received revision: 17 November 1999 / Accepted: 15 December 1999 相似文献
6.
Identification and partial characterization of proteins and proteoglycans encrusting the secondary cell walls of flax fibres 总被引:3,自引:0,他引:3
Four proteins were isolated from depectinised elementary fibres of flax (Linum usitatissimum L.), using either alkali or cellulase digestion treatments. All the four proteins were characterized by a deficiency or low
contents of hydroxyproline and by high levels of glutamic acid/glutamine and/or aspartic acid/asparagine. The two proteoglycans
solubilized with cellulase strongly reacted with β-glucosyl Yariv reagent but not with α-glucosyl Yariv reagent and contained
appreciable amounts of alanine, glycine, serine and threonine, suggesting a relationship with cell wall hydroxyproline-deficient
arabinogalactan-proteins. The two alkali-extracted proteins did not show any reaction with β-glucosyl Yariv dye. Due to the
harsh treatment, they might only partially represent the original proteins. Due to its high level of glycine (41%), one of
these proteins might be classified as a glycine-rich protein. The latter polypeptide, of low molecular molar mass, contained
14.6% leucine and might consist of a domain related to leucine-rich proteins. The data show that these proteins and arabinogalactan-protein-like
proteoglycans were strongly associated with the secondary walls of flax fibres. Their presence in small amounts (0.1–0.4%),
raises the problem of their putative structural role.
Received: 22 October 1999 / Accepted: 17 January 2000 相似文献
7.
Methyl ent-17-hydroxy-16β-kauran-19-oate was fed to a 2-day-old culture of the fungus Rhizopus stolonifer, fermenting at room temperature (25 °C) in an orbital shaker (2 l). After 11 days, both broth and mycelia were extracted
with ethyl acetate. Two novel compounds were isolated from this experiment: methyl ent-9α,17-dihydroxy-16β-kauran-19-oate and methyl ent-7α,17-dihydroxy-16β-kauran-19-oate. Their structures were fully confirmed by spectroscopic methods.
Received: 22 July 1999 / Received revision: 2 November 1999 / Accepted: 12 November 1999 相似文献
8.
Kim HS Yoon BD Choung DH Oh HM Katsuragi T Tani Y 《Applied microbiology and biotechnology》1999,52(5):713-721
One yeast strain, SY16, was selected as a potential producer of a biosurfactant, and identified as a Candida species. A biosurfactant produced from Candida sp. SY16 was purified and confirmed to be a glycolipid. This glycolipid-type biosurfactant lowered the surface tension of
water to 29 dyne/cm at critical micelle concentration of 10 mg/l (1.5 × 10−5 M), and the minimum interfacial tension was 0.1 dyne/cm against kerosene. Thin-layer and high-pressure liquid chromatography
studies demonstrated that the glycolipid contained mannosylerythritol as a hydrophilic moiety. The hydrophilic sugar moiety
of the biosurfactant was determined to be β-d-mannopyranosyl-(1 → 4)-O-meso-erythritol by nuclear magnetic resonance (NMR) and fast atom bombardment mass–spectroscopy analyses. The hydrophobic moiety,
fatty acids, of the biosurfactant was determined to be hexanoic, dodecanoic, tetradecanoic, and tetradecenoic acid by gas
chromatography–mass spectroscopy. The structure of the native biosurfactant was determined to be 6-O-acetyl-2,3- di-O-alkanoyl-β-d-mannopyranosyl-(1 → 4)-O-meso-erythritol by NMR analyses. We newly determined that an acetyl group was linked to the C-6 position of the d-mannose unit in the hydrophilic sugar moiety.
Received: 18 December 1999 / Received last revision: 2 June 1999 / Accepted: 4 June 1999 相似文献
9.
An extremely halotolerant mannan-degrading bacterium (strain NN) was isolated from the Great Salt Lake, Utah, USA. Strain
NN grew at salinities from 0 to 20% NaCl with optimal growth at 0% NaCl. When grown on 0.2% (w/v) locust bean gum as the carbon
source at 10% NaCl, both β-mannanase and β-mannosidase activities were produced. β-Mannosidase activity was shown to be cell-associated,
while at least 23% of the total β-mannanase activity was extracellular. The optimum temperature and pH for β-mannanase activity
were 70 °C and 7.6, and for β-mannosidase 25 °C and 7.0. The β-mannanase system retained full activity after 24 h of incubation
at 60 °C and 10% NaCl. β-Mannanase activity was maximal at 1% NaCl and β-mannosidase activity at 0.5% NaCl. Despite these
low salinity optima, 50% and 100% respectively of the initial β-mannanase and β-mannosidase activities remained after 48 h
of incubation at 20% NaCl, indicating a high degree of halostability. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis
revealed the presence of at least eight different mannan-degrading proteins in the cell-free culture supernatant of cultures
grown on locust bean gum.
Received: 19 March 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998 相似文献
10.
During the glyoxysomal β-oxidation of long-chain acyl-CoAs, short-chain intermediates accumulate transiently (Kleiter and
Gerhardt 1998, Planta 206: 125–130). The studies reported here address the underlying factors. The studies concentrated upon
the aspects of (i) chain length specificity and (ii) metabolic regulation of the glyoxysomal β-oxidation of sunflower (Helianthus annuus L.) cotyledons. (i) Concentration-rate curves of the β-oxidation of acyl-CoAs of various chain lengths showed that the β-oxidation
activity towards long-chain acyl-CoAs was higher than that towards short-chain acyl-CoAs at substrate concentrations <20 μM.
At substrate concentrations >20 μM, long-chain acyl-CoAs were β-oxidized more slowly than short-chain acyl-CoAs because the
β-oxidation of long-chain acyl-CoAs is subject to substrate inhibition which had already started at 5–10 μM substrate concentration
and results from an inhibition of the multifunctional protein (MFP) of the β-oxidation reaction sequence. However, low concentrations
of free long-chain acyl-CoAs are rather likely to exist within the glyoxysomes due to the acyl-CoA-binding capacity of proteins.
Consequently, the β-oxidation rate towards a parent long-chain acyl-CoA will prevail over that towards the short-chain intermediates.
(ii) Low concentrations (≤5 μM) of a long-chain acyl-CoA exerted an inhibitory effect on the β-oxidation rate of butyryl-CoA.
Reversibility of the inhibition was observed as well as metabolization of the inhibiting long-chain acyl-CoA. Regarding the
activities of the individual β-oxidation enzymes towards their C4 substrates in the presence of a long-chain acyl-CoA, the MFP activity exhibited strong inhibition. This inhibition appears
not to be due to the detergent-like physical properties of long-chain acyl-CoAs. The results of the studies, which are consistent
with the observation that short-chain intermediates accumulate transiently during complete degradation of a long-chain acyl-CoA,
suggest that the substrate concentration-dependent chain-length specificity of the β-oxidation and a metabolic regulation
at the level of MFP are factors determining this transient accumulation.
Received: 2 February 1999 / Accepted: 14 April 1999 相似文献
11.
Osmotic water permeability of isolated vacuoles 总被引:5,自引:0,他引:5
We measured the osmotic water permeability (P
os) of vacuoles isolated from onion (Allium cepa L.), rape (Brassica napus L.), petunia (Petunia hybrida Hook.) and red beet (Beta vulgaris L.). For all the vacuolar types investigated, P
os values were in the range 200–1000 μm s−1. The change in membrane surface area induced by an osmotic gradient was smaller than 2–6%. The vacuolar P
os values for red beet and onion were reduced by 1 mM HgCl2, to 14% and 30% of the control values, respectively, but were partially restored to 51% and 76% by 5 mM β-mercaptoethanol.
These results suggest that aquaporins were present in all the vacuoles tested. In HgCl2-treated onion vacuoles, the reduced P
os (56 μm s−1) had a low activation energy (approx. 6 kJ mol−1), indicating that water permeation was still occurring mainly via aquaporins, and that the water permeability of the lipid
part of the vacuolar membrane is probably very low.
Received: 18 February 1999 / Accepted: 21 June 1999 相似文献
12.
Warwicker J 《Planta》2001,212(3):343-347
Sequence comparison indicates that auxin-binding protein 1 (ABP1) belongs to a family of proteins with the core β-barrel
structure of the vicilins. Previous modelling within this family correctly predicted metal-ion binding and oligomeric properties
of oxalate oxidase. ABP1 also contains a putative metal-ion-binding cluster of amino acids, adjacent to a tryptophan side
chain, leading to a proposed auxin-binding site that incorporates metal-ion interaction with the auxin carboxylate. Modelling
implicates W44 (Zea mays ABP1) in auxin binding, rather than W136 or W151. Reduced sequence similarity for the C-terminal region prevents model building.
It is proposed that one of these C-terminal tryptophans, along with a neighbouring negatively charged side chain, occupies
the binding pocket in the absence of auxin, thereby linking auxin binding to conformational change and C-terminal involvement
in signalling.
Received: 10 December 1999 / Accepted: 4 August 2000 相似文献
13.
Torres R Ramón F de la Mata I Acebal C Castillón MP 《Applied microbiology and biotechnology》1999,53(1):81-84
At 28 °C, Streptomyces lavendulae produced high levels of penicillin V acylase (178 IU/l of culture) when grown on skim milk as the sole nutrient source for
275 h. The enzyme showed catabolite repression by glucose and was produced in the stationary phase of growth. Penicillin V
was a good inducer of penicillin V acylase formation, while phenoxyacetic acid, the side-chain moiety of penicillin V, did
not alter enzyme production significantly. The enzyme was stable between pH 6 and 11 and at temperatures from 20 °C to 55 °C.
This extracellular enzyme was able to hydrolyse natural penicillins and unable to hydrolyse penicillin G.
Received: 22 March 1999 / Received revision: 16 June 1999 / Accepted: 20 June 1999 相似文献
14.
Synthesis and degradation of a 28-kDa pod storage protein in French bean (Phaseolus vulgaris) plants
Pod storage protein (PSP) accumulated in developing pods of French bean (Phaseolus vulgaris L.) plants, and increasing the PSP mRNA level by pod removal resulted in the enhancement of PSP accumulation in pods that
formed later. Pod storage protein was detected in flowers, young leaves and young stem internodes in addition to pods. Accumulation
of PSP and its mRNA was induced by sink-removal in an organ-specific manner. In addition, wounding induced PSP accumulation
systemically in leaves. Methyl jasmonate did not induce PSP synthesis but enhanced the synthesis that was induced by wounding.
In senescing pods, PSP was degraded, and degradation products with molecular masses of 20 and 17 kDa were detected in the
pods. The amount of 20-kDa degradation product was greater than that of the 17 kDa product.
Received: 26 May 1999 / Accepted: 24 June 1999 相似文献
15.
M. H. Dicko M. J. F. Searle-van Leeuwen G. Beldman O. G. Ouedraogo R. Hilhorst A. S. Traoré 《Applied microbiology and biotechnology》1999,52(6):802-805
Curculigo pilosa is traditionally used in the manufacture of sorghum beer in West Africa. β-Amylase was purified 100-fold with 38% yield from
a crude extract, giving final specific activities of 4850 U/mg and 5650 U/mg using soluble starch and p-nitrophenyl maltopentaoside, respectively, as substrates. The molecular mass of the monomeric enzyme was 64 kDa and its pI
4.2. Both activity and thermostability are higher than reported for other plant β-amylases. The catalytic efficiency was lower
for amylose than for starches and amylopectin. In contrast to other plant amylases, the β-amylase from C. pilosa is able to degrade raw starches from wheat, corn, potato and rice. In this respect, it resembles β-amylases from microbial
origin. This property, and its high activity and stability, explain its traditional use in the manufacture of infant food
and sorghum beer in Burkina Faso and could make it applicable for other biotechnological purposes.
Received: 4 March 1999 / Received revision: 6 August 1999 / Accepted: 13 August 1999 相似文献
16.
J. Q. Liu S. Ito T. Dairi N. Itoh S. Shimizu H. Yamada 《Applied microbiology and biotechnology》1998,49(6):702-708
Low-specificity l-threonine aldolase, catalyzing the reversible cleavage/condensation reaction between l-threonine/l-allo-threonine and glycine plus acetaldehyde, was purified to homogeneity from Pseudomonas sp. NCIMB 10558. The enzyme has an apparent molecular mass of approximately 145 kDa and consists of four identical subunits
with a molecular mass of 38 kDa. The enzyme, requiring pyridoxal- 5′-phosphate as a coenzyme, is strictly l-specific at the α position, whereas it can not distinguish between threo and erythro forms at the β position. Besides the reversible cleavage/condensation of threonine, the enzyme also catalyzes the reversible
interconversion between glycine plus various aldehydes and l-β-hydroxy-α-amino acids, including l-β-(3,4-dihydroxyphenyl)serine, l-β-(3,4-met‐hylenedioxyphenyl)serine and l-β-phenylserine, providing a new route for the industrial production of these important amino acids.
Received: 10 November 1997 / Received revision: 7 January 1998 / Accepted 30 January 1998 相似文献
17.
Ermel FF Follet-Gueye ML Cibert C Vian B Morvan C Catesson AM Goldberg R 《Planta》2000,210(5):732-740
The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen
(Populus tremula L. × P. tremuloides Michx.) using biochemical and immunocytochemical methods. Comparisons were also made between active and resting tissues.
Active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. Use of antibodies
raised against arabinan side chains of rhamnogalacturonan 1 (LM6), as well as biochemical analysis, revealed an obvious decrease
from the cortex to the differentiating xylem. Galactan side chains, detected with LM5 antibodies, were present mainly in the
cambial zone and enlarging xylem cells. In contrast, they were totally absent from sieve-tube cell walls. Image analysis of
LM5 immunogold labelling in the cambial zone showed a clustered distribution of galactan epitopes in the radial walls, a distribution
which might result from the association of two different periodic processes, namely the exocytosis of galactan and wall expansion.
Cessation of cambial activity was characterized by cell wall thickening accompanied by a sharp decrease in the relative amount
of pectin and a lowering of the degree of methylesterification. The data provide evidence that the walls of phloem and xylem
cells differ in their pectin composition even at a very early stage of commitment. These differences offer useful tools for
identifying the initial cells among their immediate neighbours.
Received: 12 June 1999 / Accepted: 20 October 1999 相似文献
18.
Cappello S Liu NX Musselli C Brezicka FT Livingston PO Ragupathi G 《Cancer immunology, immunotherapy : CII》1999,48(9):483-492
Fucosyl-GM1 (Fuc-GM1) [Fucα1 → 2Galβ1 → 3GalNAcβ1 → 4(NeuAcα2-3)Galβ1 → 4Glcβ1 → O-Cer] is a small-cell-lung-cancer (SCLC)-associated ganglioside initially defined by the murine monoclonal antibody F12. On
the basis of its known distribution, Fuc-GM1 is a potential target for active immunotherapy in SCLC patients. Fuc-GM1 has
been extracted and purified from bovine thyroid. The immunogenicity of Fuc-GM1 was tested in mice either alone, mixed with
carrier protein keyhole limpet hemocyanin (KLH) or covalently linked with KLH, plus immunological adjuvant QS-21. The Fuc-GM1-KLH
conjugate plus QS-21 adjuvant was found to be optimal. It induced consistent IgM and IgG enzyme-linked immunosorbent assay
(ELISA) titers against Fuc-GM1. These antibodies were strongly reactive with the strongly Fuc-GM1-positive rat hepatoma cell
line H4-II-E, and they were moderately reactive with the moderately positive human SCLC cell line H146 by flow cytometry and
complement-mediated lysis. Both ELISA and fluorescence-activated cell sorting (FACS) reactions were inhibited with Fuc-GM1or
H4-II-E but not with the structurally related ganglioside GM1 or Fuc-GM1-negative colon cancer cell line LS-C. On the basis
of these results, a vaccine comprising Fuc-GM1-KLH plus QS-21 is being prepared for testing in patients with SCLC.
Received: 25 March 1999 / Accepted: 5 August 1999 相似文献
19.
Genetically transformed plants of a phalaenopsis orchid [Doritaenopsis Coral Fantasy×Phalaenopsis (Baby Hat×Ann Jessica)] were regenerated after cocultivation of cell clumps with Agrobacterium tumefaciens strains LBA4404 (pTOK233) and EHA101 (pIG121Hm) that harbored genes for β-glucuronidase (GUS) and hygromycin resistance.
The efficiency of transformation was markedly increased by 10 h cocultivation of cell clumps with A. tumefaciens that had been induced with 200 μm acetosyringone, and by inclusion of 500 μm acetosyringone in the cocultivation medium. Hygromycin-resistant cell clusters (0.5–3 mm in diameter) were selected from
the infected cell clumps after 4–6 weeks of culture on agar (8 g/l)-solidified new Dogashima medium (NDM) containing 20 g/l
sucrose, 0.1 mg/l naphthaleneacetic acid, 1.0 mg/l benzyladenine (BA), 50 mg/l hygromycin and 300 mg/l cefotaxime. The cell
clusters proliferated 4 weeks after transfer onto the same medium. To induce callus greening, the carbon source was changed
from sucrose to maltose. The green calli obtained produced protocorm-like bodies (PLBs) after 4 weeks of culture on phytohormone-free
NDM medium. Regeneration of transgenic plantlets was enhanced by incubating PLBs on NDM medium supplemented with 0.1 mg/l
abscisic acid, followed by partial desiccation for 10–30 min. Successful transformation was confirmed by histochemical GUS
assay, PCR analysis and Southern hybridization of transformants. With this transformation system, more than 100 hygromycin-resistant
phalaenopsis plantlets were produced about 7 months following infection of the cell aggregates.
Received: 10 November 1998 / Revision received: 4 June 1999 / Accepted: 22 June 1999 相似文献
20.
Screening and characterization of bioflocculant produced by isolated Klebsiella sp. 总被引:18,自引:0,他引:18
Sixteen strains of polymer-producing bacteria were isolated from the activated sludge samples taken from two seafood processing
plants in Southern Thailand. Their culture broths possessed the ability to flocculate kaolin suspension in the presence of
1% CaCl2. Based on the flocculating activity, the strain S11 was selected and identified to be a Klebsiella sp. using the partial 16S rRNA sequencing method. The growth of the isolated Klebsiella sp. was maximal (1.026 g l−1 dry cell mass) after 1 day cultivation while the highest polymer yield (0.973 g l−1) was achieved after 5 days cultivation. The flocculating activity of the culture broth, however, was highest after 2 days
cultivation. The polymer was identified to be an acidic polysaccharide containing neutral sugar and uronic acid as its major
and minor components, respectively. Results on the properties of the partially purified polysaccharide from Klebsiella sp. S11 revealed that it consisted of galactose, glucose and mannose in an approximate ratio of 5:2:1. It was soluble in
acidic or basic solutions but not in organic solvents. Its molecular mass was greater than 2 × 106 Da. Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl groups in its molecules. Differential scanning
calorimetry of the polysaccharide indicated the crystalline melting point (T
m) at 314 °C. The optimum dosage of polysaccharide to give the highest flocculating activity was 15 mg l−1 in the presence of 1% CaCl2.
Received: 8 February 1999 / Received last revision: 4 June 1999 / Accepted: 4 June 1999 相似文献