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991.
Piotr Ceglowski Alexander Boitsov Natalia Karamyan Sunghee Chai Juan C. Alonso 《Molecular genetics and genomics : MGG》1993,241(5-6):579-585
The low-copy-number and broad-host-range pSM19035-derived plasmid pBT233 is stably inherited in Bacillus subtilis cells. Two distinct regions, segA and segB, enhance the segregational stability of the plasmid. Both regions function in a replicon-independent manner. The maximization of random plasmid segregation is accomplished by the recombination proficiency of the host or the presence of the pBT233 segA region. The segA region contains two open reading frames (or?) [α and β]. Inactivation or deletion of or?β results in SegA? plasmids. Better than random segregation requires an active segB region. The segB region contains two or?s (or?? and or?ζ). Inactivation of either of the orfs does not lead to an increase in cell death, but or?ζ? plasmids are randomly segregated. These results suggest that pBT233 stabilization relies on a complex system involving resolution of plasmid oligomers (segA) and on the function(s) encoded by the segB region. 相似文献
992.
Agnieszka Domka Roman Jędrzejczyk Rafał Ważny Maciej Gustab Michał Kowalski Michał Nosek Jakub Bizan Markus Puschenreiter Marek Vaculίk Ján Kováč Piotr Rozpądek 《Plant, cell & environment》2023,46(1):268-287
Toxic metal pollution requires significant adjustments in plant metabolism. Here, we show that the plant microbiota plays an important role in this process. The endophytic Sporobolomyces ruberrimus isolated from a serpentine population of Arabidopsis arenosa protected plants against excess metals. Coculture with its native host and Arabidopsis thaliana inhibited Fe and Ni uptake. It had no effect on host Zn and Cd uptake. Fe uptake inhibition was confirmed in wheat and rape. Our investigations show that, for the metal inhibitory effect, the interference of microorganisms in plant ethylene homeostasis is necessary. Application of an ethylene synthesis inhibitor, as well as loss-of-function mutations in canonical ethylene signalling genes, prevented metal uptake inhibition by the fungus. Coculture with S. ruberrimus significantly changed the expression of Fe homeostasis genes: IRT1, OPT3, OPT6, bHLH38 and bHLH39 in wild-type (WT) A. thaliana. The expression pattern of these genes in WT plants and in the ethylene signalling defective mutants significantly differed and coincided with the plant accumulation phenotype. Most notably, down-regulation of the expression of IRT1 solely in WT was necessary for the inhibition of metal uptake in plants. This study shows that microorganisms optimize plant Fe and Ni uptake by fine-tuning plant metal homeostasis. 相似文献
993.
Wojciech Wasowicz Piotr Wolkanin Marek Bednarski Jolanta Gromadzinska Maria Sklodowska Krystyna Grzybowska 《Biological trace element research》1993,38(2):205-215
Selenium (Se), copper (Cu), and zinc (Zn) concentrations were determined in plasma of 64 mothers at delivery, 58 nonpregnant women, 64 neonates, and 12 infants, aged 2–12 mo. Se and Zn concentrations in mothers at delivery were significantly lower, and Cu higher than in nonpregnant women. Mean Se and Cu concentrations in newborns were statistically lower than those in mothers at delivery, and Zn and Cu concentrations in preterm infants (n=13) were significantly higher than in fullterm infants (n=51). Maternal parity had no significant influence on the distribution of plasma trace element levels. No significant differences were observed in Se and Zn levels in maternal and cord blood plasma according to birth weight, contrary to maternal Cu concentration. Significant correlations were found between maternal and cord blood Se content, and between maternal plasma Cu concentration and birth weight of neonates. 相似文献
994.
Mucha Piotr Rekowski Piotr Szyk Agnieszka Kupryszewski Gotfryd Giel-Pietraszuk Małgorzata Barciszewski Jan 《International journal of peptide research and therapeutics》1998,5(5-6):345-348
The Tat wild-type fragment of sequence Arg49-Lys-Lys-Arg52-Arg-Gln-Arg-Arg-Arg57-NH2 (labelled as Tat1) and three analogues of this fragment with the substitution Arg52 → D-Arg52 (labelled as Tat2) or L-citrulline (Cit) (labelled as Tat3) or L-ornithine (Orn) (labelled as Tat4) were synthesized to study Tat-TAR RNA HIV-1 (27-nucleotide fragment of sequence 5′-AGAUCUGAGCCUGGAGCUCUCU-3′) interactions by circular dichroism. α-helical structure was the most readily adopted by the Tat3 analogue with Arg52 → Cit substitution. All the peptides investigated caused conformational changes in the TAR structure. The most dramatic changes were observed for the Tat2-TAR complex. 相似文献
995.
Piotr Walczak Helena Oberman Ralph C. Kirkwood Bjorn Kristiansen 《Applied microbiology and biotechnology》1984,20(2):129-132
Summary The effect of the herbicides MCPA, MCPB, mecoprop, dichlorprop, 2,4-D, 2,4-DB, and 2,4,5-T on l-lysine fermentation was investigated using a lysine-producing mutant of Corynebacterium glutamicum. Stimulation of l-lysine production by 6% to 36% was observed in shaken flask experiments when the test herbicides were added at a concentration of 5 · 10-4 M to growing cultures after 24 h of cultivation. The most effective stimulators were MCPA, mecoprop and dichlorprop.Detailed studies of the effect of MCPA (5 · 10-6 M to 5 · 10-3 M) showed that the degree of stimulation depended on medium composition and aeration. In the synthetic medium, maximum production of 50 g · l-1 lys · HCl occurred at 5 · 10-4 M MCPA and an oxygen transfer rate (OTR) of 1.97 g O2 · l-1 · h-1, while 61.7 g · l-1 of lys · HCL was formed at 5 · 10-3 M MCPA and an OTR of 3.75 g O2 · l-1 · h-1. In the amino-nitrogen rich medium, maximum production of 42 g · l-1 lys · HCl was observed at 5 · 10-6 M MCPA and an oxygen transfer rate of 1.5 g O2 · l-1 · h-1. Results from batch l-lysine fermentation in a fermenter showed similar stimulatory effects, with an optimal concentration of MCPA for l-lysine production of 5 · 10-5 M. Without herbicide addition, the test strain produced 16.25 g · l-1 of product and with addition of 5 · 10-5 M MCPA, the same strain produced 52.1 g · l-1 lys · HCl after 72 h of fermentation.Abbreviations MCPA
2-methyl-4-chlorophenoxyacetic acid
- MCPB
2-methyl-4-chlorophenoxybutyric acid
- mecoprop
2-methyl-4-chlorophenoxypropionic acid
- dichlorprop
2,4-dichlorophenoxypropionic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- 2,4-DB
2,4-dichlorophenoxybutyric acid
- 2,4,5-T
2,4,5-trichlorophenoxyacetic acid 相似文献
996.
Krzysztof Darłak Zbigniew Grzonka Pawel Krzaścik Piotr Janicki S.Witold Gumułka 《Peptides》1984,5(4):687-689
Seventeen analogues of dermorphin were synthesized and bio-assayed to determine the influence of side chains of the individual amino acid residues forming the sequence of dermorphin on the biological activity of this opioid peptide. Syntheses were carried out using solid-phase procedure, and the analogues obtained were purified by gel filtration on Sephadex G-10. Biological activities determined in guinea pig ileum (GPI) and mouse vas deferens (MVD) tests showed that the N-terminal tetrapeptide is responsible for the activity of dermorphin. Substitutions in the C-terminal fragment, particularly in position 5, for other amino acid residues results in substantial differentiation towards mu and delta receptors. 相似文献
997.
The determination of U and Th was carried out on pooled samples of muscle tissue of cod (Gadus morhua), herring (Clupea harengus), sprat (Sprattus sprattus) and some other species of fish caught in 1981 in the southern Baltic. The levels of U obtained in the present study are
generally within the ranges presented by other authors for fish from different aquatic regions of the world. The concentrations
of U are similar to those found for Th in Baltic fish analysed. The concentration factors CFU(Th), discrimination factors DFU/Th and Th/U ratios (by weight) were calculated and discussed. These coefficients were also compared with values determined in
other Baltic organisms. Transfer of U and Th along a food chain from potential prey (diet) to fish as predator (consumer)
was quantified with a transfer factor. 相似文献
998.
999.
In coupled mitochondria of maize, inorganic pyrophosphate has no effect on electron transport whereas it competitively inhibits state 3 (with addition of ADP) respiration. The degree of inhibition depends on the ADP concentration in the reaction medium. At 150 and 30O μM ADP, the inhibition constant (Ki) has a value of 1.1 × 10−4 M. Pyrophosphate either does not penetrate throucvh the membranes or penetrates through them in only very small amounts. It does not inhibit the exchange 32PiPi; however, it undergoes an exchange with ADP (2 nmol PPi/mg protein for 10 min at 30°). 相似文献
1000.
Density-dependent predation ofChaoborus flavicans onDaphnia longispina in a small lake: the effect of prey size 总被引:3,自引:3,他引:0
Piotr I. Krylov 《Hydrobiologia》1992,239(3):131-140
Functional response curves of fourth instar larvae ofChaoborus flavicans preying on two size classes ofDaphnia longispina were examined throughout three summer seasons in a small forest lake. Data for each size class were fitted to Holling's disc equation. The parametersa (attack rate) andTh (handling time) were calculated for each prey size from these curves. Attack rate was greater and handling time was shorter for small (0.77 mm) than for large (1.82 mm)Daphnia. In 1:1 mixture of these prey size classes the predation rates ofChaoborus on smallDaphnia at prey densities above 20 l–1 were greater than predicted from the single size-class experiments. The observed predation rates on largeDaphnia were lower than predicted at all prey densities. Since both single size-class and two size-class experiments were run during the same period of time the difference in observed and predicted predation rates could not be attributed to seasonal changes in prey preference ofChaoborus larvae. In experiments with a concentrated mixture of lake zooplankton (dominated byD. longispina)Chaoborus preference forDaphnia decreased as prey body size increased. There was no obvious correlation between selectivity coefficients and size-frequency distributions ofDaphnia. When medium-sizedDaphnia were omitted from calculations the preference of small over large prey did not differ significantly from the predictions of the single size-class model. 相似文献