共查询到20条相似文献,搜索用时 15 毫秒
1.
R. L. Wolff Bernard Comps Anne M. Marpeau Laurent G. Deluc 《Trees - Structure and Function》1997,12(2):113-118
The fatty acid compositions of the seed oils from ten pine species have been established by capillary gas-liquid chromatography
of the methyl esters. With regard to either normal fatty acids or Δ5-olefinic acids, the general pattern of fatty acids did
not differ from that of other pine seed oils reported previously. The main fatty acid was linoleic (9,12–18:2) acid (44.4–57.1%),
followed by either oleic (9–18:1) acid (13.4–24.5%) or pinolenic (5,9,12–18:3) acid (1.5–25.2%). When applying multivariate
analyses to the chemometric data (13 variables) of 49 pine species (ca. 40% of the living pine species), it was possible to
distinguish between several sections: Pinea, Longifolia, Halepensis, Ponderosa-Banksiana, Sylvestris, and Cembra. The latter section was clearly divided into two sub-groups. A few species that presented a low overall content of Δ5-olefinic
acids, and that grow in warm-temperate regions, were isolated from the bulk of other pine species. It is hypothesized that
Δ5-olefinic acids might be related to cold-acclimation.
Received: 5 June 1997 / Accepted: 17 August 1997 相似文献
2.
Phase behaviour and crystallinity of plant cuticular waxes studied by Fourier transform infrared spectroscopy 总被引:1,自引:0,他引:1
The phase behaviour of cuticular waxes from leaves of Hedera helix L. and Juglans regia L. was studied by Fourier transform infrared spectroscopy. For this purpose reconstituted waxes, isolated cuticular membranes,
dewaxed polymer matrix membranes and whole leaves were studied in the horizontal attenuated total reflection and transmission
modes. Melting curves of cuticular waxes were derived from temperature-dependent changes in the absorption maximum of the
symmetric stretching mode of CH2 groups (νs, at approx. 2856–2848 cm−1). With increasing temperature absorption band doublets due to CH2 scissoring (δsciss) and rocking (δrock) movements (at approx. 1473–1471 and 730–720 cm−1, respectively) indicative of an orthorhombic arrangement of alkyl chains merged into a single peak. The area ratio of the
peaks at approx. 720 and 730 cm−1 was used as a measure for aliphatic crystallinity of plant cuticular waxes at a given temperature. The investigations of
reconstituted cuticular waxes and those still embedded in isolated cuticles or in situ on the leaf produced comparable results.
The findings are discussed in terms of the properties of the cuticular transport barrier.
Received: 21 March 1997 / Accepted: 25 April 1997 相似文献
3.
T. C. Tricas J. G. New 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):89-101
Elasmobranch fishes localize weak electric sources at field intensities of <5 ηV cm−1, but the response dynamics of electrosensory primary afferent neurons to near threshold stimuli in situ are not well characterized.
Electrosensory primary afferents in the round stingray, Urolophus halleri, have a relatively high discharge rate, a regular discharge pattern and entrain to 1-Hz sinusoidal peak electric field gradients
of ≤20 ηV cm−1. Peak neural discharge for units increases as a non-linear function of stimulus intensity, and unit sensitivity (gain) decreases
as stimulus intensity increases. Average peak rate-intensity encoding is commonly lost when peak spike rate approximately
doubles that of resting, and for many units occurs at intensities <1 μV cm−1. Best neural sensitivity for nearly all units is at 1–2 Hz with a low-frequency slope of 8 dB/decade and a high-frequency
slope of −23 dB/decade. The response characteristics of stingray electrosensory primary afferents indicate sensory adaptations
for detection of extremely weak phasic fields near 1–2 Hz. We argue that these properties reflect evolutionary adaptations
in elasmobranch fishes to enhance detection of prey, communication and social interactions, and possibly electric-mediated
geomagnetic orientation.
Accepted: 20 June 1997 相似文献
4.
Tetrahydrofolate was shown to function as a methyl acceptor in the anaerobic demethylation of dimethylsulfoniopropionate
to methylthiopropionate in cell extracts of the sulfate-reducing bacterium strain WN. Dimethylsulfoniopropionate-dependent
activities were 0.56 μmol methyltetrahydrofolate min–1 (mg protein)–1 and were higher than required to explain the growth rate of strain WN on dimethylsulfoniopropionate. The reaction did not
require ATP or reductive activation by titanium(III)-nitrilotriacetic acid. Preincubation of the extract under air significantly
decreased the activity (35% loss in 3 h). Three other dimethylsulfoniopropionate-demethylating sulfate reducers, Desulfobacterium niacini, Desulfobacterium vacuolatum, and Desulfobacterium strain PM4, had dimethylsulfoniopropionate:tetrahydrofolate methyltransferase activities of 0.16, 0.05, and 0.24 μmol min–1 (mg protein)–1, respectively. No methyltransferase activity to tetrahydrofolate was found with betaine as a substrate, not even in extracts
of betaine-grown cells of these sulfate reducers. Dimethylsulfoniopropionate demethylation in cell extracts of strain WN was
completely inhibited by 0.5 mM propyl iodide; in the light, the inhibition was far less strong, indicating involvement of
a corrinoid-dependent methyltransferase.
Received: 24 June 1997 / Accepted: 29 August 1997 相似文献
5.
Xanthobacter tagetidis grew as a chemolithotrophic autotroph on thiosulfate and other inorganic sulfur compounds, as a heterotroph on thiophene-2-carboxylic
acid, acetic acid and α-ketoglutaric acid, and as a mixotroph on thiosulfate in combination with thiophene-2-carboxylic acid
and/or acetic acid. Autotrophic growth on one-carbon organosulfur compounds, and intermediates in their oxidation are also
reported. Thiosulfate enhanced the growth yields in mixotrophic cultures, presumably by acting as a supplementary energy source,
since ribulose bisphosphate carboxylase was only active in thiosulfate-grown cells and was not detected in mixotrophic cultures
using thiosulfate with thiophene-2-carboxylic acid. Bacteria grown on thiophene-2-carboxylic acid also oxidized sulfide, thiosulfate
and tetrathionate, indicating these as possible sulfur intermediates in thiophene-2-carboxylic acid degradation. Thiosulfate
and tetrathionate were oxidized completely to sulfate and, consequently, did not accumulate as products of thiophene-2-carboxylic
acid oxidation in growing cultures. K
m and V
max values for the oxidation of thiosulfate, tetrathionate or sulfide were 13 μM and 83 nmol O2 min–1 (mg dry wt.)–1, respectively; thiosulfate and tetrathionate became autoinhibitory at concentrations above 100 μM. The true growth yield
(Ymax) on thiophene-2-carboxylic acid was estimated from chemostat cultures (at dilution rates of 0.034–0.094 h–1) to be 112.2 g mol–1, with a maintenance coefficient (m) of 0.3 mmol thiophene-2-carboxylic acid (g dry wt.)–1 h–1, and the maximum specific growth rate (μmax) was 0.116 h–1. Growth in chemostat culture at a dilution rate of 0.041 h–1 indicated growth yields [g dry wt. (mol substrate)–1] of 8.1 g (mol thiosulfate)–1, 60.9 g (mol thiophene-2-carboxylic acid)–1, and 17.5 g (mol acetic acid)–1, with additive yields for growth on mixtures of these substrates. At a dilution rate of 0.034 h–1, yields of 57.8 g (mol α-ketoglutaric acid)–1 and 60.7 g (mol thiophene-2-carboxylic acid)–1 indicated some additional energy conservation from oxidation of the thiophene-sulfur. SDS-PAGE of cell-free preparations
indicated a polypeptide (M
r, 21.0 kDa) specific to growth on thiophene-2-carboxylic acid for which no function can yet be ascribed: no metabolism of
thiophene-2-carboxylic acid by cell-free extracts was detected. It was shown that X. tagetidis exhibits a remarkable degree of metabolic versatility and is representative of facultatively methylotrophic and chemolithotrophic
autotrophs that contribute significantly to the turnover of simple inorganic and organic sulfur compounds (including substituted
thiophenes) in the natural environment.
Received: 1 July 1997 / Accepted: 3 November 1997 相似文献
6.
Despite the well-characterized function of the green-algal eyespot apparatus as a combined absorption/reflection screen for
the photoreceptor for phototaxis, little is known about the proteins involved in the formation of this complex organelle.
We therefore purified the carotenoid-rich lipid globules, which are the most conspicuous component of the eyespot sensu strictu
from Spermatozopsis similis Preisig et Melkonian. Electron microscopy and an average carotenoid:chlorophyll ratio of 51, confirmed the high purity of
the fraction. The diameter of isolated globules (approx. 112 nm) fell within their in vivo range (90–120 nm). Absorption spectra
in aqueous media peaked at 535 nm. The predominant carotenoids were β,ψ-, β, β- and δ-carotene. Freeze-fracture studies with
cells and whole-mount electron microscopy of isolated globules demonstrated regularly arranged particles at the globule surface.
Sodium dodecyl sulfate–polyacrylamide gel electrophresis revealed specific enrichment of 10 tightly bound major proteins and
several minor proteins with the globules. Proteases were used to analyze their topology and function. Upon treatment with
thermolysin, globules were released from a fraction enriched in isolated eyespot apparatuses. Major proteins of these globules,
and those treated with thermolysin after isolation, were identical. However, the purified proteins were sensitive to thermolysin,
indicating that domains of them are normally hidden in the globule matrix. In contrast, pronase degraded all globule-associated
proteins in situ. These globules were not stable and easily fused, whereas thermolysin-treated globules were relatively stable.
Lipase did not affect globule stability. These results indicate that the five thermolysin-resistant proteins (apparent M
r values: 56, 52, 32, 29, 27 kDa) are close to the surface and might be crucial for globule stabilization, whereas the thermolysin-accessible
proteins are probably involved in globule/globule interactions and/or globule/eyespot-membrane interactions.
Received: 19 June 2000 / Accepted: 4 October 2000 相似文献
7.
The ability of Alcaligenes eutrophus to grow and produce polyhydroxyalkanoates (PHA) on plant oils was evaluated. When olive oil, corn oil, or palm oil was fed
as a sole carbon source, the wild-type strain of A. eutrophus grew well and accumulated poly(3-hydroxybutyrate) homopolymer up to approximately 80% (w/w) of the cell dry weight during
its stationary growth phase. In addition, a recombinant strain of A. eutrophus PHB−4 (a PHA-negative mutant), harboring a PHA synthase gene from Aeromonas caviae, was revealed to produce a random copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate from these plant oils with a high
cellular content (approximately 80% w/w). The mole fraction of 3-hydroxyhexanoate units was 4–5 mol% whatever the structure
of the triglycerides fed. The polyesters produced by the A. eutrophus strains from olive oil were 200–400 kDa (the number-average molecular mass). The results demonstrate that renewable and inexpensive
plant oils are excellent carbon sources for efficient production of PHA using A. eutrophus strains.
Received: 3 September 1997 / Received revision: 10 November 1997 / Accepted: 16 November 1997 相似文献
8.
P. J. M. Teunissen H. J. Swarts J. A. Field 《Applied microbiology and biotechnology》1997,47(6):695-700
Ligninolytic basidiomycetes were screened for their ability to produce the tetrachlorinated hydroquinone metabolites drosophilin
A (DA, tetrachloro-4-methoxyphenol) and drosophilin A methyl ether (DAME, tetrachloro-1,4-dimethoxybenzene). Five fungal strains
produced these metabolites in detectable amounts, including strains from Bjerkandera and Peniophora, which are genera not previously known for DA or DAME production. Phellinus fastuosus ATCC26.125 had the highest and most reliable production of DA and DAME in peptone medium, respectively 15–60 μM and 4–40 μM.
This fungus was used to study culture conditions that could increase DAME production. A fourfold increase in DAME production
was found after the addition of hydroquinone to growing cultures of P. fastuosus. Therefore, hydroquinone is postulated to be a possible biosynthetic precursor of DAME in the fungus. Antagonising P. fastuosus by adding filter-sterilised culture fluid of a competing fungus, Phlebia radiata, increased DAME production significantly by tenfold. This result suggests that DAME production is elicited by compounds present
in the culture fluid of P. radiata, indicating that DAME has an antibiotic function in P. fastuosus.
Received: 17 September 1996 / Received revision: 7 February 1997 / Accepted: 15 February 1997 相似文献
9.
10.
T. Sasamura T. Kobayashi S. Kojima H. Qadota Y. Ohya I. Masai Y. Hotta 《Molecular & general genetics : MGG》1997,254(5):486-494
We have isolated eight genes from Drosophila, small GTPases. They can be classified into three rab family genes (Drab2, Drab5, Drab11) and five rho family genes (Drac1a, Drac1b, Drac3, Dcdc42, DrhoA). While Drac3 is a novel type of rac gene, others are homologues of known mammalian genes for small GTPases. Northern blot analyses showed that all the genes
are expressed throughout all developmental stages from embryo to adult. In situ hybridization to embryos revealed that Drab2, Drac1b, and Drac3 are highly expressed in the nervous system, in the trunk mesoderm, and in the cephalic mesoderm, respectively. Since hemocytes
are derived from the cephalic mesoderm, we carried out double stainings using a hemocyte marker – anti-peroxidasin antibody
– and Drac3 in situ hybridization. We found that Drac3 is expressed in hemocyte precursor cells. In the Drac3 deficiency embryos, the hemocyte precursor cells start to differentiate normally, but never develop into mature hemocytes,
indicating that Drac3 is essential for their maturation. The DrhoA and Dcdc42 genes complemented S. cerevisiae rho1 and cdc42 mutations in the same manner as human rhoA and CDC42, respectively. These results suggest functional similarity between Drosophila and mammalian small GTPase genes.
Received: 7 May 1996 / Accepted: 6 January 1997 相似文献
11.
Boris Zarda D. Hahn Antonis Chatzinotas Wilhelm Schönhuber Alexander Neef Rudolf I. Amann Josef Zeyer 《Archives of microbiology》1997,168(3):185-192
In situ hybridization with rRNA-targeted, fluorescent (Cy3-labeled) oligonucleotide probes was used to analyze bacterial community
structure in ethanol- or paraformaldehyde-fixed bulk soil after homogenization of soil samples in 0.1% pyrophosphate by mild
ultrasonic treatment. In ethanol-fixed samples 37 ± 7%, and in paraformaldehyde 41 ± 8% of the 4′, 6-diamidino-2-phenylindole(DAPI)-stained
cells were detected with the bacterial probe Eub338. The yield could not be increased by enzymatic and/or chemical pretreatments
known to enhance the permeability of bacterial cells for probes. However, during storage in ethanol for 7 months, the detectability
of bacteria increased in both ethanol- and paraformaldehyde-fixed samples to up to 47 ± 8% due to an increase in the detection
yield of members of the α-subdivision of Proteobacteria from 2 ± 1% to 10 ± 3%. Approximately half of the bacteria detected
by probe Eub338 could be affiliated to major phylogenetic groups such as the α-, β-, γ-, and δ-subdivisions of Proteobacteria,
gram-positive bacteria with a high G+C DNA content, bacteria of the Cytophaga-Flavobacterium cluster of the CFB phylum, and the planctomycetes. The analysis revealed that bacteria of the α- and δ-subdivision of Proteobacteria
and the planctomycetes were predominant. Here, members of the α-subdivision of Proteobacteria accounted for approximately
10 ± 3% of DAPI-stained cells, which corresponded to 44 ± 16 × 108 cells (g soil, dry wt.)–1, while members of the δ-subdivision of Proteobacteria made up 4 ± 2% of DAPI-stained cells [17 ± 9 × 108 cells (g soil, dry wt.)–1]. A large population of bacteria in bulk soil was represented by the planctomycetes, which accounted for 7 ± 3% of DAPI-stained
cells [32 ± 12 × 108 cells (g soil, dry wt.)–1]. The detection of planctomycetes in soil confirms previous reports on the occurrence of planctomycetes in soil and indicates
a yet unknown ecological significance of this group, which to date has never been isolated from terrestrial environments.
Received: 29 March 1997 / Accepted: 28 May 1997 相似文献
12.
A yeast artificial chromosome (YAC) contig from the C57BL/6 (H2
b
) mouse was created from the major histocompatibility complex (Mhc, H2 in mouse) class Ib subregion, H2-M. It spans approximately 1.2 megabase (Mb) pairs and unites the previous >1.5-Mb YAC contigs (Jones et al. 1995) into a single
contig, which includes 21 Mhc class I genes distal to H2-T1. A bacterial artificial chromosome (BAC) contig from the 129 (H2
bc
) mouse, spanning approximately 600 kilobases, was also built from Znf173 (Afp, a gene for acid finger protein), through Tctex5 (t-complex testis expressed-5) and Mog (myelin oligodendrocyte glycoprotein), to H2-M2. Twenty-four sequence-tagged site (STS) markers were newly developed, and 35 markers were mapped in the YAC/BAC contigs,
which define the marker order as Cen –Znf173–Tctex5 – Mog–D17Tu42–D17Mit232–H2-M3–D17Leh525–H2-M2– Tel. The gene order of Znf173 – Tctex5 – Mog – D17Tu42 is conserved between mouse and human, showing that the middle H2-M region corresponds to the subregion of the human Mhc surrounding HLA-A.
Received: 25 July 1997 / Revised: 10 September 1997 相似文献
13.
Takuya Uehara Hideshi Naka Shigeru Matsuyama Tetsu Ando Hiroshi Honda 《Applied Entomology and Zoology》2012,47(3):227-232
The sex pheromones of two species of hawk moth, Deilephila elpenor lewisii (Butler) and Theretra oldenlandiae oldenlandiae (Fabricius), were analyzed using gas chromatography–electroantennographic detection (GC–EAD) and GC–mass spectrometry (GC–MS). Two and three EAD-active components were found in D. elpenor lewisii and T. oldenlandiae oldenlandiae, respectively. GC–MS analyses using authentic compounds and extracts derivatized by dimethyl disulfide and 4-methyl-1,2,4-triazoline-3,5-dione identified the two components in D. elpenor lewisii as (E)-11-hexadecenal (E11–16:Ald) and (10E,12E)-10,12-hexadecadienal (E10,E12–16:Ald), and the three in T. oldenlandiae oldenlandiae as E11–16:Ald, E10,E12–16:Ald, and (10E,12Z)-10,12-hexadecadienal (E10,Z12–16:Ald). In field-trap tests, no males of either species were attracted to any single components. Male moths of D. elpenor lewisii were specifically attracted to a binary blend of E11–16:Ald and E10,E12–16:Ald at a ratio of 85:15, whereas males of T. oldenlandiae oldenlandiae were attracted to a ternary blend of E11–16:Ald, E10,Z12–16:Ald and E10,E12–16:Ald at a ratio of 30:40:30. We therefore conclude that the sex pheromone of D. elpenor lewisii is a mixture of E11–16:Ald and E10,E12–16:Ald and that of T. oldenlandiae oldenlandiae is E11–16:Ald, E10,Z12–16:Ald and E10,E12–16:Ald. 相似文献
14.
Telomeric length and telomerase activity vary with age in peripheral blood cells obtained from normal individuals 总被引:21,自引:0,他引:21
Hiroshi Iwama K. Ohyashiki Junko H. Ohyashiki Shigifumi Hayashi Naoyuki Yahata Keiko Ando Keisuke Toyama Akinori Hoshika Masaru Takasaki Mayumi Mori Jerry W. Shay 《Human genetics》1998,102(4):397-402
The telomerase activity and length of telomeres of peripheral blood mononuclear cells obtained from 124 healthy individuals
aged 4–95years was measured. Telomerase activity level was semiquantitatively assessed by a fluorescent-telomeric repeat amplification
protocol (fluorescent-TRAP) using an internal telomerase assay standard, fluorescent primers and an automated laser fluorescent
DNA sequencer. Telomeric length, measured by assay of terminal restriction fragments (TRFs), was determined in HinfI-digested DNA by Southern blot analysis using a (TTAGGG)4 probe. TRF length was determined in 80 individuals and age-related progressive reduction of size was observed. TRF length
in peripheral blood mononuclear cells obtained from normal individuals (aged 4–39years) decreased by approximately 84bp per
year, while in individuals aged ≥40years it decreased by 41bp per year. In contrast, telomerase activity showed an apparent biphasic pattern with aging. Individuals
aged 4–39years showed a progressive decrease in telomerase activity, whereas 65% of those aged ≥40years showed relatively stable but very low telomerase activity, and the remaining individuals aged ≥40years had no detectable telomerase activity. These data obtained from normal individuals might in the future be of value
to help risk stratify and manage the care of patients with leukemia.
Received: 18 August 1997 / Accepted: 10 December 1997 相似文献
15.
Mucor circinelloides LU M40 and Penicillium aurantiogriseum P 35 produce extracellular β-glycosidases that are active on the cyanogenic glycoside amygdalin. From the culture broths
of M. circinelloides, only one β-glycosidase could be identified, while two different enzymes – both having amygdalase activity – were found in
culture broths of P. aurantiogriseum. The study of the mechanism of hydrolysis of the β-bis-glycoside amygdalin with purified enzymes from the two organisms indicated
a possible sequential (two-step) reaction. In all cases, the first step of hydrolysis from amygdalin to prunasin was very
rapid, while the second step from prunasin to cyanohydrin was much slower. No cyanohydrin lyase activity was found in the
culture broths of either fungus.
Received: 16 May 1997 / Accepted: 11 September 1997 相似文献
16.
A dense accumulation of the phototrophic consortium “Pelochromatium roseum” in a small, eutrophic, freshwater lake (Dagowsee, Brandenburg, Germany) was investigated. Within the chemocline, the number
of epibionts of the consortia represented up to 19% of the total number of bacteria. Per “P. roseum” a mean value of 20 epibionts was determined. Similar to other aquatic habitats, consortia in the Dagowsee were found only
at low light intensities (< 7 μmol quanta m–2 s–1) and low sulfide concentrations (0–100 μM). In dialysis cultures of “P. roseum”, bacterial cells remained in a stable association only when incubated at light intensities between 5 and 10 μmol quanta
m–2 s–1. Intact consortia from natural samples had a buoyant density of 1046.8 kg m–3, which was much higher than that of ambient chemocline water (995.8 kg m–3). Under environmental conditions and without motility, this density difference would result in rapid sedimentation of consortia
toward the lake bottom. Our results indicate that (1) consortia are adapted to a very narrow regime of light intensities and
sulfide concentrations, (2) motility and tactic responses must be of ecological significance for the colonization of the free
water column of lakes, and (3) phototrophic growth of consortia can be explained only by a cycling of sulfur species in the
chemocline, possibly within the consortia themselves.
Received: 27 May 1997 / Accepted: 16 September 1997 相似文献
17.
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
18.
19.
Detection of Microbial Pathogens in Shellfish with Multiplex PCR 总被引:16,自引:0,他引:16
Cynthia W. Brasher Angelo DePaola Daniel D. Jones Asim K. Bej 《Current microbiology》1998,37(2):101-107
Multiplex PCR amplification of uidA, cth, invA, ctx, and tl genes was developed enabling simultaneous detection in shellfish of Escherichia coli, an indicator of fecal contamination and microbial pathogens, Salmonella typhimurium, Vibrio vulnificus, V. cholerae, and V. parahaemolyticus, respectively. Each of the five pairs of oligonucleotide primers was found to support PCR amplifications of only its targeted
gene. The optimized multiplex PCR reaction utilized a PCR reaction buffer containing 2.5 mM MgCl2 and primer annealing temperature of 55°C. Oyster tissue homogenate seeded with these microbial pathogens was subjected to
DNA purification by the Chelex™ 100 (BioRad) method. The sensitivity of detection for each of the microbial pathogens was
≤101–102 cells following a “double” multiplex PCR amplification approach. Amplified target genes in a multiplex PCR reaction were
subjected to a colorimetric GeneComb™ (BioRad) DNA-DNA hybridization assay. This assay was rapid and showed sensitivity of
detection comparable to the agarose gel electrophoresis method. The colorimetric GeneComb™ assay avoids use of hazardous materials
inherent in conventional gel electrophoresis and radioactive-based hybridization methods. Multiplex PCR amplification, followed
by colorimetric GeneComb™ DNA-DNA hybridization, has been shown to be an effective, sensitive, and rapid method to detect
microbial pathogens in shellfish.
Received: 17 November 1997 / Accepted: 17 February 1998 相似文献
20.
Overexpression of a cytosolic hydroxymethylglutaryl-CoA reductase leads to squalene accumulation in yeast 总被引:4,自引:0,他引:4
The enzyme 3-hydroxy-3-methylglutaryl-coenzyme-A (HMG-CoA) reductase is known as the rate-limiting enzyme in early sterol
biosynthesis in eukaryotic cells. To eliminate this regulation in the yeast Saccharomyces cerevisiae, a truncated HMG1 gene, producing a form of the enzyme that lacks the membrane-binding region (i.e. amino acids 1–552), was constructed and
overexpressed in this yeast. The transformed strains accumulated large amounts of the sterol precursor squalene, while the
levels of ergosterol and a number of other sterol compounds were only slightly elevated. These findings suggest that HMG-CoA
reductase is not the only rate-limiting step in sterol synthesis and its overexpression cannot significantly influence this
pathway beyond the sterol precursor squalene.
Received: 9 June 1997 / Received revision: 1 September 1997 / Accepted: 19 September 1997 相似文献