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1.
2.
R. J. M. van Veen H. den Dulk-Ras R. A. Schilperoort P. J. J. Hooykaas 《Plant molecular biology》1987,8(1):105-108
Summary The chromosomal genes chvA and chvB of Agrobacterium tumefaciens, which mediate attachment to plant cells, were found to be essential not only for tumour induction but also for the formation of root nodules on plants. 相似文献
3.
Temporary disturbance of translocation of assimilates in douglas firs caused by low levels of ozone and sulfur dioxide 总被引:4,自引:0,他引:4 下载免费PDF全文
Douglas firs (Pseudotsuga menziesii [Mirb.] Franco) are suffering strongly from air pollution in western Europe. We studied the effect of low concentrations of ozone (200 micrograms per cubic meter during 3 days) and sulfur dioxide (53 micrograms per cubic meter during 28 days) on translocation of assimilates in 2 year old Douglas firs. The trees were exposed to the pollutants and afterward transferred to a growth chamber adapted to the use of 14CO2. Root/soil respiration was measured daily. The results showed a significant decrease of the 14CO2 root/soil respiration during the first 1 to 2 weeks after exposure to either ozone or sulfur dioxide. The ultimate level of 14CO2 root/soil respiration did not differ significantly, which suggests a recovery of the exposed trees during the first weeks after exposure. 相似文献
4.
C. F. C. Bonting H. W. van Veen A. Taverne G. J. J. Kortstee A. J. B. Zehnder 《Archives of microbiology》1992,158(2):139-144
The response of Acinetobacter strain 210A to low phosphate concentrations was investigated in P- or C-limited chemostat cultures. The organism accumulated poly--hydroxybutyric acid under P-deprivation, at phosphate concentrations ranging from 0.1 to 0.7 mM. The amount of biomass was proportional to the phosphate concentration in the medium and no polyphosphate was formed. When shifting a culture from P- to C-limitation phosphate was accumulated as polyphosphate. No poly--hydroxybutyrate could be detected in these cells. The amount of polyphosphate in the cell showed a hysteresis. When cultures were shifted from low to high phosphate concentrations, polyphosphate reached a maximum of about 60 mg P per gram of dry weight at about 3 times excess phosphate (ca. 2.5 mM Pi). It decreased to 45 mg P per gram dry weight at approximately 5 times the phosphate needed for growth (ca. 3.5 mM Pi). In the reverse case (high to low) polyphosphate did never exceed 45 mg P per gram dry weight. The specific activities of alkaline phosphatase and the phosphate uptake system were induced at residual Pi concentrations below the detection limit (<10 M). The specific uptake rate followed also a hysteresis. The specific activities of polyphosphatase and polyphosphate: AMP phosphotransferase increased when polyphosphate formation was possible.Abbreviations HPP
High polymeric polyphosphates
- PHB
Poly--hydroxybutyric acid
- PPn
Polyphosphate
- PQQ
Pyrrolo-quinoline quinone
- U
1 mol product formed · min-1 相似文献
5.
NH(4)-Excreting Azospirillum brasilense Mutants Enhance the Nitrogen Supply of a Wheat Host 总被引:1,自引:0,他引:1
Spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense were selected on the basis of their excretion of NH(4). Two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mM) concentrations of NH(4). The nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of the wild type. The mutants excreted substantial amounts of ammonia when they were grown either under oxygen-limiting conditions (1 kPa of O(2)) or aerobically on nitrate or glutamate. The mutants grew well on glutamate as a sole nitrogen source but only poorly on NH(4)Cl. Both mutants failed to incorporate [C]methylamine. We demonstrated that nitrite ammonification occurs in the mutants. Wild-type A. brasilense, as well as the mutants, became established in the rhizospheres of axenically grown wheat plants at levels of > 10 cells per g of root. The rhizosphere acetylene reduction activity was highest in the preparations containing the mutants. When plants were grown on a nitrogen-free nutritional medium, both mutants were responsible for significant increases in root and shoot dry matter compared with wild-type-treated plants or with noninoculated controls. Total plant nitrogen accumulation increased as well. When they were exposed to a N(2)-enriched atmosphere, both A. brasilense mutants incorporated significantly higher amounts of N inside root and shoot material than the wild type did. The results of our nitrogen balance and N enrichment studies indicated that NH(4)-excreting A. brasilense strains potentially support the nitrogen supply of the host plants. 相似文献
6.
Smit E van Elsas JD van Veen JA de Vos WM 《Applied and environmental microbiology》1991,57(12):3482-3488
The transfer of a genetically marked derivative of plasmid RP4, RP4p, from Pseudomonas fluorescens to members of the indigenous microflora of the wheat rhizosphere was studied by using a bacteriophage that specifically lyses the donor strain and a specific eukaryotic marker on the plasmid. Transfer of RP4p to the wheat rhizosphere microflora was observed, and the number of transconjugants detected was approximately 10 transconjugants per g of soil when 10 donor cells per g of soil were added; transfer in the corresponding bulk soil was slightly above the limit of detection. All of the indigenous transconjugants which we analyzed contained a 60-kb plasmid and were able to transfer this plasmid to a Nx RpP. fluorescens recipient strain. The indigenous transconjugants were identified as belonging to Pseudomonas spp., Enterobacter spp., Comamonas spp., and Alcaligenes spp. 相似文献
7.
8.
Jan-Willem Taanman Anneke Y. van der Veen Cobi Schrage Hans de Vries Charles H. C. M. Buys 《Human genetics》1991,87(3):325-327
Summary A cloned, 40 kb, genomic DNA fragment, containing the last exon of the gene for human cytochrome c oxidase subunit VIb and its flanking sequences, was used as a probe to localize the subunit VIb gene on human metaphase chromosomes. The probe was labelled with Bio-11-dUTP and detected by fluorescence. Subsequent R-banding indicated that the cytochrome c oxidase subunit VIb gene is localized in band 19q13.1, extending the evidence that the human nuclear genes of cytochrome c oxidase are not clustered. 相似文献
9.
B. A. Prior C. P. Kenyon ‡ Michelle van der Veen J. P. Mildenhall 《Journal of applied microbiology》1987,62(2):119-128
When Pseudomonas fluorescens was grown in a glucose salts medium adjusted with NaCl to a water activity (aw ) value of 0.980, the intracellular glutamic acid concentration increased 23-fold and comprised 90% of the total amino acid pool. This increase was not observed when the aw of the medium was reduced to 0.980 with sorbitol. Sorbitol was taken up rapidly over a 30 min period and accumulated intracellularly to a level approximately two-fold greater than the concentration in the growth medium. In continuous culture, the specific rate of glutamic acid production and glucose uptake was greater at 0.980 (NaCl) than at 0.997 aw . The maintenance coefficients for glucose uptake were similar at both aw values but were 2.4-fold greater for glutamic acid production at 0.980 (NaCl) than at 0.997 aw . 相似文献
10.
J.D. van Elsas A.F. Dijkstra J.M. Govaert J.A. van Veen 《FEMS microbiology letters》1986,38(3):151-160
Abstract Antibiotic-resistant strains of Pseudomonas fluorescens and Bacillus subtilis , produced by transposon Tn5 mutagenesis and transformation with plasmid pFT30, respectively, were characterized. Both strains grew at a rate comparable to that of the wild-type strains, and the antibiotic resistance remained stable for over 50 generations without selective pressure. During the growing season, the survival of these strains was studied in two soils of different texture cropped with wheat. The B. subtilis populations declined rapidly in both soils and then stabilized at the levels of added spores. P. fluorescens showed a slow, steady decline in both soils; survival was better in the finer-textured soil, a silt loam, than in the coarser loamy sand. For both bacteria, some translocation to deeper soil layers was observed. No significant rhizosphere effects were detected in either of the two soils. 相似文献