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991.
The measurement of natural 15N abundance is a well-established technique for the identification and quantification of biological N2 fixation in plants. Associative N2 fixing bacteria have been isolated from sugarcane and reported to contribute potentially significant amounts of N to plant growth and development. It has not been established whether Australian commercial sugarcane receives significant input from biological N2 fixation, even though high populations of N2 fixing bacteria have been isolated from Australian commercial sugarcane fields and plants. In this study, 15N measurements were used as a primary measure to identify whether Australian commercial sugarcane was obtaining significant inputs of N via biological N2 fixation. Quantification of N input, via biological N2 fixation, was not possible since suitable non-N2 fixing reference plants were not present in commercial cane fields. The survey of Australian commercially grown sugarcane crops showed the majority had positive leaf 15N values (73% >3.00, 63% of which were >5.00), which was not indicative of biological N2 fixation being the major source of N for these crops. However, a small number of sites had low or negative leaf 15N values. These crops had received high N fertiliser applications in the weeks prior to sampling. Two possible pathways that could result in low 15N values for sugarcane leaves (other than N2 fixation) are proposed; high external N concentrations and foliar uptake of volatilised NH3. The leaf 15N value of sugarcane grown in aerated solution culture was shown to decrease by approximately 5 with increasing external N concentration (0.5–8.0 mM), with both NO3
– and NH4
+ nitrogen forms. Foliar uptake of atmospheric NH3 has been shown to result in depleted leaf 15N values in many plant species. Acid traps collected atmospheric N with negative 15N value (–24.45±0.90) from above a field recently surface fertilised with urea. The 15N of leaves of sugarcane plants either growing directly in the soil or isolated from soil in pots dropped by 3.00 in the same field after the fertiliser application. Both the high concentration of external N in the root zone (following the application of N-fertilisers) and/or subsequent foliar uptake of volatilised NH3 could have caused the depleted leaf 15N values measured in the sugarcane crops at these sites. 相似文献
992.
Extracellular polysaccharides (EPSs) produced by an Erwinia spp. associated with a fungal canker disease of Eucalyptus were fractionated into two polysaccharides, one that was identified with that produced by Erwinia stewartii. The other has a similar structure, but with one terminal Glc residue replaced by pyruvic acid to give 4,6-O-[(R)-1-carboxyethylidene)-Galp. Their structures were determined using a combination of chemical and physical techniques including methylation analysis, periodate oxidation, low-pressure gel filtration and anion-exchange chromatographies, high-pH anion-exchange chromatography, mass spectrometry and 1D and 2D 1H NMR spectroscopy. The new polysaccharides, identified as EPS Futululu FF-1 and FF-2, have the following structures:The molecular weights of the polysaccharides range from 1.3-2.1x10(6) and their hydrodynamic properties are those of polydisperse, polyanionic biopolymers with pseudoplastic, non-thixotropic flow characteristics in aqueous solutions. 相似文献
993.
Survival of several <Emphasis Type="Italic">Rhizobium/Bradyrhizobium</Emphasis> strains on different inoculant formulations and inoculated seeds 总被引:1,自引:0,他引:1
F. Temprano M. Albareda M. Camacho A. Daza C. Santamaría Nombre D. Rodríguez-Navarro 《International microbiology》2002,5(2):81-86
The effect of a variety factors on the survival of several rhizobia strains on inoculants and inoculated seeds has been evaluated.
Since the rhizobia strains showed different cell-density-evolution patterns on peat-based inoculants and on inoculated seeds,
several inoculant formulations with highly effective Rhizobium/Bradyrhizobium strains (for Lupinus, Hedysarum, Phaseolus and Glycine max.) were monitored under the following storage conditions: (a) the inoculants were kept refrigerated (at 4 °C), or (b) at room
temperature (25 °C). The effect of water content (30–50%, w/w) in the inoculants as well as that of several seed-coating adhesives
were also investigated. Alternative carriers including perlite and vermiculite were tested. For all of the strains, survival
on sterile peat-based inoculants was higher than on the corresponding unsterile peat formulation; for the latter, refrigerated
storage conditions are recommended to ensure high bacterial densities. The water content of the inoculants had a differential
effect on strain survival depending on the sterility of the peat, such that a high water content was more detrimental when
unsterilized peat was employed. The best adherent for rhizobia survival was a gum arabic/water solution. Perlite was as effective
as peat in maintaining a high population of rhizobia, at least for 6 months of storage.
Electronic Publication 相似文献
994.
van der Gast CJ Knowles CJ Starkey M Thompson IP 《Journal of industrial microbiology & biotechnology》2002,29(1):20-27
The aim of this research was to determine the effectiveness of a strategy for constructing microbial consortia for treating
chemically mixed industrial effluent, based on a more thorough understanding of communities within waste metal-working fluids
(MWFs). Complementary phenotypic and genotypic methods revealed that the microbial communities in spent MWFs had low diversity
and were very similar in species composition in samples originating from different locations and uses. Of 65 bacterial isolates
studied, only 9 species were identified using fatty acid methyl ester (FAME) analysis. The results of genotypic analysis by
denaturing gradient gel electrophoresis (DGGE) were congruent with observations made using FAME analysis. The metabolic potential
of the isolates was assessed in terms of assimilation ability and tolerance of co-contaminants. The three isolates, selected
(Clavibacter michiganensis, Methylobacterium mesophilicum, and Rhodococcus erythropolis) to form a consortium, were representative of three of the four most abundant populations and when combined could utilise'or
tolerate all of the individual MWF components, including the biocide and the recalcitrant compound benzotriazole. Journal of Industrial Microbiology & Biotechnology (2002) 29, 20–27 doi:10.1038/sj.jim.7000271
Received 19 December 2001/ Accepted in revised form 02 May 2002 相似文献
995.
A total of 180 samples of poultry feeds were collected during 1996 and 1997 from different factories in the south of the province
of Córdoba-Argentina. They were examined for the occurrence of Penicillium spp. and Aspergillus group species. Likewise, the
capacity to produce aflatoxins by the Aspergillus section flavi group was determined. The predominant species of Aspergillus
were A. flavus and A. parasiticus. For Penicillium spp., P. brevicompactum, P. purpurogenum and P. oxalicum were identified.
Less frequently isolated were A. candidus, A. fumigatus, A. niger, A. orizae, A. parvulus, A. tamarii, A. terreus, and P.
expansum, P. funiculosum, P. minioluteum, P. pinophylum, P. restrictum, P. variabile and others. The mean value counts ranged
from 1 × 103 to 9.5 × 104 CFU/g for the Aspergillus spp. and from 1.2 × 103 to 2.5 × 105 CFU/g for the Penicillium spp. When
cultured on autoclaved rice kernels for 1 week in the dark at 25°C, mycotoxin production by strains of A. flavus was as follows:
21 of the 45 assayed strains (47%) produced aflatoxins. From them, 24% of the isolates produced AFB1 and AFB2 with levels
from 181 to 14 545 and 6 to 3640 μg/kg respectively. Only 10 strains produced AFB1 with levels from 10 to 920 μg/kg. Fifty
percent of the A. parasiticus strain was toxicogenic; six aflatoxicogenic profiles were identified. Only 10% of the strains
produced all of the aflatoxins. These results showed that a potential exists for the production of mycotoxins by the Aspergillus
section flavi and the Penicillium spp. They also suggested an association of mycotoxicosis with poultry feeds in Argentina.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
996.
ROBERT F KARYEIJA RICHARD W GIBSON JARI P T VALKONEN 《The Annals of applied biology》1998,133(1):39-44
Sweet potato virus disease (SPVD), the most harmful disease of sweet potatoes in East Africa, is caused by mixed infection with sweet potato feathery mottle potyvirus (SPFMV) and sweet potato chlorotic stunt crinivirus (SPCSV). Wild Ipomoea spp. native to East Africa (J cairica, I. hildebrandtii, I. involucra and J wightii) were graft-inoculated with SPVD-affected sweet potato scions. Inoculated plants were monitored for symptom development and tested for SPFMV and SPCSV by grafting to the indicator plant J setosa, and by enzyme-linked immunosorbent assay (ELISA). Virus-free scions of sweet potato cv. Jersey were grafted onto these wild Ipomoea spp. in the field, and scions collected 3 wk later were rooted in the greenhouse and tested for viruses using serological tests and bioassays. In all virus tests, J cairica and J involucra were not infected with either SPFMV or SPCSV. J wightii was infected with SPFMV, but not SPCSV, in the field and following experimental inoculation; J hildebrandtii was infected with SPCSV, but not SPFMV, following experimental inoculation. These data provide the first evidence of East African wild Ipomoea germplasm resistant to the viruses causing SPVD. 相似文献
997.
Iris bulbs and Crocus corms were planted at two planting dates in sandy soil infested with Pythium spp. At monthly intervals during the growing season root rot infection was assessed over 3 consecutive years and disease development curves were predicted for both crops. The disease development was remarkably different for Iris and Crocus and the curve shape was determined by the crop rather than by the Pythium species. Planting date had a significant effect on disease development in both crops. No correlation was found between disease development and soil temperature. 相似文献
998.
The influence of relative plant density and floral morphological complexity on the behaviour of bumblebees 总被引:1,自引:1,他引:0
We assessed the combined effects of varying the relative density and the relative floral morphological complexity of plant
species on the behaviour of their bumblebee pollinators. Three species of bumblebee (Bombus pascuorum, B. terrestris and B. hortorum) were observed foraging on experimental arrays consisting of pair-wise combinations of four plant species: Borago officinalis, Phacelia tanacetifolia (both with simple flowers), Antirrhinum majus and Linaria vulgaris (both with complex flowers). Plant arrangements consisted of either two simple-flower species, a simple with a complex species
or two complex species. The number of plants in each array was constant, while the frequency of each species was manipulated
so that it was either rare, equal or common compared with its competitor. Contrary to predictions, rare plants were actually
at an advantage in terms of the number of bees attracted per plant. However, rare plants were at a disadvantage in terms of
pollen wastage because foragers more often went to a flower of another species after visiting a rare plant. The behaviour
of bees on each plant species was further affected by plant floral complexity and the identity of the other species in the
array. The three bumblebee species were markedly different in their foraging behaviour and in their responses to varying floral
density and complexity. Each species preferred particular flower species. The results are discussed with reference to resource
partitioning among bumblebee species.
Received: 29 July 1998 / Accepted: 5 October 1998 相似文献
999.
Localization of Fe-containing superoxide dismutase in cyanobacteria from the Baltic Sea: depth and light dependency 总被引:2,自引:0,他引:2
The abundance and cellular location of Fe-containing superoxide dismutase (Fe-SOD) in trichomes of Nodularia , Aphanizomenon and Anabaena collected from various depths in the Baltic Sea, and in trichomes of a cultured Nodularia strain, BC Nod-9427, isolated from the Baltic Sea, was examined by immunogold labelling. For trichomes collected from natural populations the areal concentration of Fe-SOD labelling decreased with depth: trichomes collected from surface accumulations had between 8 and 11 gold particles μm−2 whereas trichomes collected from a depth of 18 m were unlabelled. When trichomes collected from a depth of 10 m (mean areal labelling density 0·5 gold particles μm−2 ) were exposed to the higher irradiances present at 1 m, the areal concentration of Fe-SOD increased to 3·5–4 gold particles μm−2 within 4 h. When cultures of Nodularia strain BC Nod-9427, adapted to low light (10 μmol m−2 s−1 ), were transferred to an incident irradiance of 1350 μmol m−2 s−1 , a doubling of the areal concentration of Fe-SOD gold label was observed within 1 h. Addition of 3-(3,4-dichlorophenyl)-1,1'-dimethylurea (DCMU) to cultures immediately before their transfer to increased illumination resulted in a decrease in areal Fe-SOD concentrations whereas addition of CdCl2 caused an increase over and above that induced by the elevated irradiance. These results suggest that Baltic Sea cyanobacteria are able to modulate their Fe-SOD content but that this might be in response to oxidative stress rather than to light per se . 相似文献
1000.