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1.
An exhaustive qualitative and quantitative profiling of the photosynthetic glycerolipids in three strains of the marine diatom
Skeletonema sp. was carried out by ultra performance liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry.
In the diatom thylakoid membrane, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) account for about
45–70% and 5–15% of the total membrane lipids, respectively. The anionic sulfoquinovosyldiacylglycerol (SQDG) as well as the
likewise anionic phosphatidylglycerol (PG) contribute between 10–40% and 4–10% each. The predominant species of MGDG were
those with C16:3/C16:3, C20:5/16:1, and C20:5/C16:3. Three main molecular species of DGDG contained C20:5/C16:1, C20:5/C16:2, and C16:1/C16:1. The major molecular species of SQDG were those containing combinations of C14:0/C14:0, C14:0/C16:0, C14:0/C16:1, and C14:0/C16:3. All the PG classes contained the C18:1/C18:1 as the main molecular species. Based on the fatty acid species in sn-2 position, it is indicated that MGDG and DGDG are biosynthesized through prokaryotic pathway exclusively within the chloroplast,
whereas PG and SQDG have a typical mixed biosynthetic pathway (both prokaryotic pathway and eukaryotic pathways). The chemical
characteristics of photosynthetic glycerolipids related with ecological physiology are discussed. 相似文献
2.
The antibiotic resistance and lipid composition of rhodococci grown in rich organic media with gaseous or liquidn-alkanes were studied. Hydrocarbon-grown rhodococci exhibited an increased resistance to a wide range of antibiotics (aminoglycosides,
linkosamides, macrolides, β-lactams, and aromatic compounds). The enhanced antibiotic resistance of rhodococci grown onn-alkanes correlated with an increased content of total cell lipids (up to 14–28%) and saturated straight-chain fatty acids
(C16:0, C18:0, C21:0) and was accompanied by the appearance of cardiolipin and phosphatidylglycerol in cells. These lipid compounds are supposed
to promote the formation of nonspecific antibiotic resistance in rhodococci by decreasing the permeability of their cell envelope
to antibiotics. 相似文献
3.
Huang HY Chen YG Wang YX Liu JH Tang SK Peng Q Wen ML Yu H Cui XL 《Extremophiles : life under extreme conditions》2008,12(6):829-835
A novel Gram-negative, slightly halophilic, catalase- and oxidase-positive, obligately aerobic bacterium, strain YIM-C248T, was isolated from a sediment sample collected from a salt-lake in the Qaidam Basin in Qinghai, north-west China. Cells were
non-sporulating short rods, occurring singly or as doublets, motile with peritrichous flagella. Growth occurred with 1–15%
(w/v) NaCl [optimum 2–4% (w/v) NaCl], at pH 6.0–10.0 (optimum pH 7.5) and at 4–35°C (optimum 25–30°C). The major cellular
fatty acids were C18:1
ω7c, C12:0 3-OH, cyclo C19:0
ω8c, C16:0 and C16:1. The predominant respiratory quinone was Q-9 and the genomic DNA G + C content was 58.6 mol%. Phylogenetic analysis based
on 16S rRNA gene sequences indicated that strain YIM-C248T should be assigned to the genus Halomonas. The sequence similarities between the isolate and the type strains of members of the genus Halomonas were in the range of 92.5–97.5%. The combination of phylogenetic analysis, DNA–DNA hybridization data, phenotypic characteristics
and chemotaxonomic differences supported the view that strain YIM-C248T represents a new species of the genus Halomonas, for which the name Halomonas sediminis sp. nov. is proposed, with YIM-C248T (=CCTCC AA 207031 = KCTC 22167) as the type strain.
The GenBank/EMBL/DBBJ accession number for the 16S rRNA gene sequence of strain YIM-C248T is EU135707. 相似文献
4.
An alga known as “Nannochloropsis”, isolated from a prawn farm in Hainan, China, has been critically investigated and identified as Chlorella, a member of the Chlorophyceae based on fatty acid composition, ultrastructure, and 18S rDNA. Cells of this alga were spherical,
measured by 1–6 μm in diameter and were enclosed in thin walls of approximately 0.04 μm thickness. They contained several
small mitochondria, two to three thylakoids and had no vacuoles. There were many pyrenoids in the algal cells and their thylakoid
lamellae were sparse and not translucent. Many lipid droplets were present in the cytoplasm. The total lipid content of this
alga was 3% per gram dry weight and its major fatty acids were C16:0, C18:0, C18:1, C18:2, C18:3 and C20:0. Eicosapentaenoic acid (C20:5, EPA) was not detected. The length of its 18S rDNA sequence was 1,712 bp. 18S rDNA sequence analyses indicated that this
alga was a species of Chlorella. 相似文献
5.
Laboratory degradation studies of two indigeneously produced linear alkyl benzenes byNocardia amarae MB-11 isolated from soil showed an overall degradation of linear alkyl benzenes isomers to the extent of 57–70%. Degradation
of 2-phenyl isomers of linear alkyl benzenes was complete and faster than that of other phenyl position (C3–C7) isomers which
were degraded to the extent of 40–72% only. Length of alkyl side chains (C10–C14) had little or no impact on the degradation pattern. Major metabolities detected were 2-, 3-and 4-phenyl butyric acids, phenyl
acetic acid and cis, cis-muconic acid. Minor metabolites weretrans-cinnamic acid, 4-phenyl 3-butenoic acid and 3-phenyl pentanoic acid along with two unidentified hydroxy acids. On the basis
of the formation pattern of these metabolities, three catabolic pathways of linear alkyl benzenes isomers inNocardia amarae MB-11 were postulated. All the phenyl position (C2–C7) isomers of C10, C12, and C14 linear alkyl benzenes along with 3-phenyl and 5-phenyl isomers of C11 and C13 linear alkyl benzenes were degraded viacis,cis-muconic acid pathway. Other phenyl position isomers of C11 and C13 linear alkyl benzenes with phenyl substitution at even number carbon atoms were principally degraded via phenyl acetic acid
pathway whiletrans-cinnamic acid formation provided a minor pathway 相似文献
6.
Da-Chun Zhuang Yi-Guang Chen Yu-Qin Zhang Shu-Kun Tang Xiao-Lei Wu Zhou-Cai Tan Wen-Jun Li Xiao-Long Cui 《Antonie van Leeuwenhoek》2009,96(3):295-301
A novel Gram-negative, catalase- and oxidase-positive, non-sporulating, rod-shaped, aerobic bacterium, designated strain JSM
078120T, was isolated from sea water collected from a tidal flat of Naozhou Island, South China Sea. Growth occurred with 1–15% (w/v)
total salts (optimum, 2–4%), at pH 6.0–10.0 (optimum, pH 7.5) and at 4–35°C (optimum, 25–30°C). The major cellular fatty acids
were C18:1
ω9c, C16:0, C12:0 3-OH and C16:1
ω7c. The predominant respiratory quinone was ubiquinone Q-9, and the genomic DNA G + C content was 60.6 mol%. Phylogenetic analysis
based on 16S rRNA gene sequences indicated that strain JSM 078120T should be assigned to the genus Marinobacter, being related most closely to the type strains of Marinobacter segnicrescens (sequence similarity 98.2%), Marinobacter bryozoorum (97.9%) and Marinobacter gudaonensis (97.6%). The sequence similarities between the novel isolate and the type strains of other recognized Marinobacter species ranged from 96.7 (with Marinobacter salsuginis) to 93.3% (with Marinobacter litoralis). The levels of DNA–DNA relatedness between strain JSM 078120T and the type strains of M. segnicrescens, M. bryozoorum and M. gudaonensis were 25.3, 20.6 and 18.8%, respectively. The combination of phylogenetic analysis, DNA–DNA relatedness, phenotypic characteristics
and chemotaxonomic data supported the view that strain JSM 078120T represents a novel species of the genus Marinobacter, for which the name Marinobacter zhanjiangensis sp. nov. is proposed. The type strain is JSM 078120T (= CCTCC AB 208029T = DSM 21077T = KCTC 22280T).
The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain JSM 078120T is FJ425903. 相似文献
7.
Analysis of Root Growth by Impedance Spectroscopy (EIS) 总被引:1,自引:0,他引:1
Electrical impedance spectroscopy (EIS) is investigated as a non-destructive method for monitoring root growth of tomato.
This paper aims to (i) review the basic principles of EIS applied to the characterisation of the different parts of the soil–root–stem-electrode
continuum, (ii) experiment the validity of the relationship between root weight and root capacitance taking into account the
influence of the soil and plant electrodes position, (iii) describe an EIS analysis of the root growth of tomato plants. All
experiments were carried out in 50 dm3 containers either in hydroponics at 930 μS for the test of root fresh or dry weight and root capacitance relationships, or
in a potting mix (oxisol) for electrode placement tests and EIS estimation of root growth. Electrical measurements of the
soil–root–stem-electrode continuum were done with a two-electrode measuring system using unpolarisable Ag–AgCl electrodes.
A ‘root cutting’ and a ‘progressively immersed root system’ experiments were carried out in order to validate the relationship
between root capacitance and root mass at 1 kHz. The effects of soil electrode and plant electrode placement were also tested,
pointing out the sensitivity of the method to the insertion height of the “plant electrode” into the stem. For the root growth
experiment, Impedance Spectra (IS) measurements were made just before harvesting the roots for dry weight and length determination.
Measurements were made 14, 22, 26 and 39 days after planting, until flowering. The IS of the soil–root–stem-electrode continuum
was modelled by a lumped electric circuit consisting of a series resistor R
0 for the soil and of four parallel resistance (R
i
)-capacitance (C
i
) circuits for the other components of the circuit. The model had nine parameters whose values were estimated by Complex Nonlinear
Least Squares curve fitting. A stepwise ascendant regression was used to identify the electrical parameters that better correlated
with root dry mass or length increment: C
3 and C
4 were well correlated with root dry mass with a r
2 of 0.975, whereas root length was explained by the combination of 1/R
3, C
3, 1/R
2 and 1/R
1 with a r
2 of 0.986. This work may be considered as a new methodological contribution to the understanding of root electrical properties
in the non-destructive diagnosis of root systems. 相似文献
8.
Pratiksha Bhadauriya Radha Gupta Surendra Singh Prakash Singh Bisen 《World journal of microbiology & biotechnology》2008,24(1):139-141
n-Alkanes pattern in response to NaCl stress has been studied in the cyanobacterium Anabaena cylindrica. Saturated hydrocarbons were separated and identified by gas chromatography-mass spectrometry (GC-MS) using serially coupled
capillary column. Light chain n-alkanes in the range of C9–C17 (43%) and heavy chain n-alkanes in range of C17–C23 (34%) and C23–C31 (23%) were identified as the major components of total hydrocarbons in the NaCl adapted cells of A. cylindrica. In contrast, NaCl-untreated cells of A. cylindrica had dominance of only long chain n-alkanes in the range of C23–C31 comprising about 94% of its total n-alkanes. The persistence of high level (43%) of short chain n-alkanes (C9–C17) in NaCl adapted cells of A. cylindrica as compared to its negligible level (0.2%) in NaCl untreated counterpart clearly indicates that NaCl stress causes the A. cylindrica to shift towards the synthesis of short chain n-alkanes. 相似文献
9.
We have investigated the role of polyunsaturated fatty acids in photosynthesis using a triple mutant of Arabidopsis thaliana that lacks trienoic fatty acids (fad 3-2 fad 7-2 fad 8). Though this mutant is male sterile, vegetative growth and development under normal conditions are largely unaffected (McConn
and Browse, 1996 Plant Cell 8: 403–416). At 0.2–1.0 kPa vapor pressure deficit (low VPD), maximum photosynthetic rates of
wild-type and mutant plants were similar while stomatal conductance rates were up to 2 times higher in mutant plants. However,
light-saturated rates of carbon assimilation and stomatal conductance in the mutant were lower than in wild-type plants when
measured at ambient (35 Pa) CO2 and 2.0–2.8 kPa vapor pressure deficit (high VPD). The limitation to photosynthesis in the mutant plants at high VPD was
overcome by saturating partial pressures of CO2 suggesting a stomatal limitation. Chlorophyll fluorescence measurements indicate that differences observed in maximum assimilation
rates were not due to limitations within the photochemical reactions of photosynthesis. Stomatal response to VPD and intrinsic
water use efficiency was drastically different in mutant versus wild-type plants. The results of this investigation indicate
that for Arabidopsis, polyunsaturated fatty acids may be an important determinant of responses of photosynthesis and stomatal conductance to environmental
stresses such as high VPD.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
The cytochrome b
6
f complex isolated from spinach chloroplast membranes can be resolved into two forms, a monomeric and a dimeric form, by centrifugation on sucrose gradients. The conversion of the dimeric form of the complex into the monomeric form could be prevented by cross-linking with the homobifunctional reagent, dithiobis(succinimidylpropionate) but not by cross-linking with disuccinimidyltartrate or glutaraldehyde. SDS-PAGE analyses of the monomeric and dimeric forms of the cytochrome complex showed the presence of specific cross-linked products in each respective form of the complex. For example, the monomeric form contained a cross-linked product of cytochrome f, cytochrome b
6
f and subunit IV while the dimeric form contained a cross-linked dimer of cytochrome b
6
f. The presence of the former in the isolated cytochrome b
6
f complex prepared by the method of Hurt and Hauska (Eur J Biochem 117: 591–599, 1981) indicates the presence of the monomer in his preparation.Abbreviations DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- DSP
dithiobis(succinimidylpropionate)
- DST
disuccinimidyltartrate 相似文献
11.
A study was undertaken on the possible involvement of phospholipids on stereospecific opiate binding to a rat brain membrane fraction comprised mainly of synaptic membranes. The addition of acidic phospholipids such as phosphatidylserine, phosphoinositides, and phosphatidic acid significantly enhanced opiate binding. With the exception of phosphatidylserine, when the acidic phospholipids contained a polyunsaturated acyl group, they were actually inhibitory, along with neutral phospholipids derived from brain. Both the C18:0, C18:1 form (derived from myelin) and the C18:0, C22:6 form of phosphatidylserine (derived from synaptic membranes) produced as much as a 45% enhancement in opiate binding. Unsaturated fatty acids were highly inhibitory, the degree of inhibition being related to the degree of unsaturation. Bot phospholipase A and C were inhibitory; and the inhibitory effect of A could not be prevented by albumin or overcome with the addition of phosphatidylserine. With the use of the cross-linking agent, dinitrodifluorobenzene, it could be demonstrated that the phosphatidylserine of synaptic membranes appeared to be preferentially associated with membrane protein. The enhancement of opiate binding by phosphatidylserine diminished with increasing degree of cross-linking. 相似文献
12.
T. Kakitani 《European biophysics journal : EBJ》1979,5(4):293-312
Using the twisted conformations of the chromophores for visual pigments and intermediates which were theoretically determined
in the previous paper, energy surfaces of the pigment at −190‡ C were obtained as functions of the torsional anglesθ
9–10 andθ
11–12 or of the torsional anglesθ
9–10 andθ
13–14. In these calculations, the existence of specific reaction paths between rhodopsin (R) and bathorhodopsin (B), between isorhodopsin
I (I) and bathorhodopsin, and between isorhodopsin II (I′) and bathorhodopsin were assumed. It was shown that the total energy
surfaces of the excited states had minimaC
1 atθ
9–10 ∼ −10‡ andθ
11–12 ∼ −80‡,C
2 atθ
9–10 ∼ −85‡ andθ
11–12 ∼ −5‡, andC
3 atθ
9–10 ∼ 0‡ andθ
13–14 ∼ −90‡. These minima are considered to correspond to the thermally barrierless common states as denoted by Rosenfeld et al.
Using the total energy surfaces in the ground and excited states, the molecular mechanism of the photoisomerization reaction
was suggested. Quantum yields for the photoconversions among R, I, I′ and B were related to the rates of vibrational relaxations,
radiationless transitions and thermal excitations. Some discussion was made of the temperature effect on the quantum yield.
Similar calculations of the energy surfaces were also made at other temperatures where lumirhodopsin or metarhodopsin I is
stable. Relative energy levels of the pigments and the intermediates were discussed. 相似文献
13.
Yi-Guang Chen Huai-Dong Xiao Shu-Kun Tang Yu-Qin Zhang Entomack Borrathybay Xiao-Long Cui Wen-Jun Li Yan-Qi Liu 《Antonie van Leeuwenhoek》2009,96(3):259-266
A pale yellow-colored, moderately halophilic, Gram-negative, catalase- and oxidase-positive, non-sporulating, rod-shaped,
motile, aerobic bacterium, designated strain JSM 073008T, was isolated from a sea anemone (Anthopleura xanthogrammica) collected from Naozhou Island, Leizhou Bay, South China Sea. The organism was able to grow with 1–20% (w/v) total salts
(optimum, 5–10%), at pH 6.0–10.0 (optimum, pH 7.5) and 10–40°C (optimum, 25–30°C). The major cellular fatty acids were C16:0, C16:1
ω7c/iso-C15:0 2-OH and C18:1
ω7c. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol and an unidentified phospholipid. The predominant
respiratory quinone was Q-8 and the genomic DNA G + C content was 47.5 mol%. Phylogenetic analysis based on 16S rRNA gene
sequences indicated that strain JSM 073008T should be assigned to the genus Alteromonas, being most closely related to Alteromonas hispanica F-32T (sequence similarity 96.9%), followed by Alteromonas genovensis LMG 24078T (96.6%) and Alteromonas litorea TF-22T (96.4%). The sequence similarities between the novel isolate and the type strains of other recognized Alteromonas species ranged from 95.9% (with Alteromonas stellipolaris ANT 69aT) to 94.5% (with Alteromonas simiduii BCRC 17572T). The combination of phylogenetic analysis, phenotypic characteristics and chemotaxonomic data supported the view that strain
JSM 073008T represents a new species of the genus Alteromonas, for which the name Alteromonas halophila sp. nov. is proposed. The type strain is JSM 073008T (=CCTCC AA 207035T = KCTC 22164T).
The authors Yi-Guang Chen and Huai-Dong Xiao have contributed equally to this work. 相似文献
14.
V. N. Popov O. V. Antipina V. P. Pchelkin V. D. Tsydendambaev 《Russian Journal of Plant Physiology》2012,59(2):177-182
Changes in the fatty acid (FA) composition of leaf and root lipids of heat-loving tobacco (Nicotiana tabacum L., cv. Samsun) plants during low-temperature hardening (8°C for 6 days) were studied. Hardening could improve leaf but not
root cold tolerance. As this took place, the relative content of polyunsaturated (18:2n-6 and 18:3n-3) FAs increased and the
proportion of saturated and monounsaturated FAs decreased. In contrast, in the roots hardening slightly increased the concentration
of saturated FAs (16:0 and 18:0) and reduced the level of unsaturated FAs (18:1n-9, 18:2n-6, and 18:3n-3). At the same time,
root lipids contained much C20–24 FAs, and their content increased during hardening. It was suggested that an increased FA saturation and elevated proportion
of C20–24 FAs in the root lipids resulting in the lower membrane fluidity could be a reason for incapability of heat-loving tobacco
plant roots of hardening and plant death at the lowtemperature stress. 相似文献
15.
Zhao W Weber C Zhang CL Romanek CS King GM Mills G Sokolova T Wiegel J 《Extremophiles : life under extreme conditions》2006,10(4):337-345
A novel thermophilic, alkali-tolerant, and CO-tolerant strain JW/WZ-YB58T was isolated from green mat samples obtained from the Zarvarzin II hot spring in the Uzon Caldera, Kamchatka (Far East Russia). Cells were Gram-type and Gram stain-positive, strictly aerobic, 0.7–0.8 μm in width and 5.5–12 μm in length and produced terminal spherical spores of 1.2–1.6 μm in diameter with the mother cell swelling around 2 μm in diameter (drumstick-type morphology). Cells grew optimally at pH25°C 8.2–8.4 and temperature 50–52°C and tolerated maximally 6% (w/v) NaCl. They were strict heterotrophs and could not use either CO or CO2 (both with or without H2) as sole carbon source, but tolerated up to 90% (v/v) CO in the headspace. The isolate grew on various complex substrates such as yeast extract, on carbohydrates, and organic acids, which included starch, d-galactose, d-mannose, glutamate, fumarate and acetate. Catalase reaction was negative. The membrane polar lipids were dominated by branched saturated fatty acids, which included iso-15:0 (24.5%), anteiso-15:0 (18.3%), iso-16:0 (9.9%), iso-17:0 (17.5%) and anteiso-17:0 (9.7%) as major constituents. The DNA G+C content of the strain is 45 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain JW/WZ-YB58T is distantly (<93% similarity) related to members of Bacillaceae. On the basis of 16S rRNA gene sequence, physiological and phenotypic characteristics, the isolate JW/WZ-YB58T (ATCC BAA-1258; DSM 17740) is proposed to be the type strain for the type species of the new taxa within the family Bacillaceae, Thermalkalibacillus uzoniensis gen. nov. sp. nov. The Genbank accession number for the 16S rRNA gene sequence is DQ221694.The Genbank accession number for the 16S rRNA gene sequence of strain JW/WZ-YB58T is DQ221694. 相似文献
16.
A. V. Ivanov A. T. Kopylov V. G. Zgoda I. Yu. Toropygin E. V. Khryapova Yu. D. Ivanov 《Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry》2009,3(4):361-371
The interaction sites for protein partners, cytochrome P450 2B4 (d-2B4) and NADPH: cytochrome P450 reductase (d-Fp), have
been identified. These proteins form complexes during their functioning. Nonspecific covalent cross-linking of the d-2B4 complexes
with d-Fp in the Emulgen 913 monomerized system was achieved by 4,4′- dithiobis-phenyl azide. Covalently cross-linked peptides
of this complex were identified by ESI-MS/MS. Several binding sites have been identified for these proteins. Based on these
sites a model for intermolecular interaction between these proteins has been proposed. This model includes 5 contact sites
on d-2B4 for d-Fp (stabilized by the cross-linker); these include the following pairs of corresponding peptides of d-2B4 and
d-Fp: 1) d-2B4324–336 and d-Fp570–585; 2) d-2B4423–433 and d-Fp102–109; 3) d-2B4327–336 and d Fp452–464; 4) d-2B4192–197 and d-Fp456–464; 5) d-2B4134–139 and d-Fp406–425. In the two last cases d-Fp peptides are located in the interdomain cleft and stabilize the protein-protein complex via the
cross-linker and so the d 2B4/d-Fp complex formation by these sites may involve amino acid residues of the peptides d-Fp456–464 and d-Fp406–425, which surround the interdomain cleft. 相似文献
17.
Soror SH Verma V Rao R Rasool S Koul S Qazi GN Cullum J 《Journal of industrial microbiology & biotechnology》2007,34(8):525-531
The genome sequence of Streptomyces coelicolor A3(2) contains 51 putative lipase and esterase genes mostly of unknown function. The gene estB (locus SCO 6966) was expressed as a His-tagged protein in E. coli. Esterase B was active at low temperatures exerting its maximum activity at 30°C and retaining more than 25% of its activity
at 4°C. The optimum pH was 8–8.5. The enzyme was active against short synthetic p-nitrophenylesters (C2–C10) with maximum activity towards the acetate ester (C2). The esterase was tested on 13 series of racemic esters of potential interest for the synthesis of chiral pharmaceutical
compounds. 4 of the series were substrates and a modest degree of enantioselectivity was observed (enantiomeric ratios of
1.1–1.9). 相似文献
18.
An approach is presented which probes the possible use of trans-[(NH3)2PtCl]+-modified deoxyoligonucleotides in the antisense strategy. It consists of (1) the selective platination of an oligonucleotide
containing 11 pyrimidine (T, C) bases as well as a single guanine (G) as a Pt-anchoring group at the 5′-end to give trans-[(NH3)2Pt{5′-d(GN7T2C2T2C2T2C}Cl]10–
1 ("antisense strand") and (2) subsequent hybridization with the purine 12-mer 5′-d(GA2G2A2G2A2G)11– ("sense strand"). According to HPLC, three major species 2–4 are formed during reaction (2), all of which are cross-linking adducts between 1 and the sense strand, as confirmed by ESI MS and melting temperature measurements. Only for the major product 3 can a structure be proposed on the basis of 1D and 2D NMR spectra. According to these, G1 of the antisense strand is cross-linked with G20 via trans-(NH3)2PtII. The complementary overhangs of the duplex represent "sticky ends" and are, in principle, capable of associating into multimers
of the duplex.
Received: 29 March 1999 / Accepted: 26 July 1999 相似文献
19.
Acetylene reduction and indoleacetic acid production by Azospirillum isolates from Cactaceous plants
Azospirillum isolates were obtained from rhizosphere soil and roots of three cactaceae species growing under arid conditions.
All Azospirillum isolates from rhizosphere and roots ofStenocereus pruinosus andStenocereus stellatus were identified asA. brasilense; isolates of surface-sterilized roots fromOpuntia ficus-indica were bothA. brasilense andA. lipoferum. Azospirilla per g of fresh root in the three species ranged from 70×103 to 11×103. The most active strains in terms of C2H2 reduction (25–49.6 nmol/h·ml) and indoleacetic acid (IAA) production (36.5–77 μg/ml) were those identified asA. brasilense and isolated from Stenocereus roots.A. lipoferum isolated from Opuntia roots produced low amounts of IAA (6.5–17.5 μg/ml) and low C2H2-reduction activity (17.8–21.2 nmol/h·ml). 相似文献
20.
Net photosynthetic rate (P
N), transpiration rate (E), stomatal conductance (g
s), leaf water potential (ψleaf), leaf nitrogen content, and photosynthetic nitrogen use efficiency (PNUE) were compared between a typical C4 plant, Agriophyllum squarrosum and a C3 plant, Leymus chinensis, in Hunshandak Sandland, China. The plant species showed different diurnal gas exchange patterns on June 12–14 when photosynthetic
photon flux density (PPFD), air temperature (T
air), and water potential were moderate. P
N, E, and g
s of A. squarrosum showed distinct single peak while those of L. chinensis were depressed at noon and had two peaks in their diurnal courses. Gas exchange traits of both species showed midday depression
under higher photosynthetic photon flux density (PPFD) and T
air when Ψleaf was significantly low down on August 6–8. However, those of A. squarrosum were depressed less seriously. Moreover, A. squarrosum had higher P
N, Ψleaf, water use efficiency (WUE), and PNUE than L. chinensis. Thus A. squarrosum was much more tolerant to heat and high irradiance and could utilise the resources on sand area more efficiently than L. chinensis. Hence species like A. squarrosum may be introduced and protected to reconstruct the degraded sand dunes because of their higher tolerance to stress and higher
resource use efficiency.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献