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1.
M W LeChevallier A Singh D A Schiemann G A McFeters 《Applied and environmental microbiology》1985,50(2):412-419
We designed experiments to assess the effect of chlorine injury on the virulence of waterborne enteropathogens. Higher chlorine doses (0.9 to 1.5 mg/liter) were necessary to produce injured Yersinia enterocolitica, Salmonella typhimurium, and Shigella spp. than to produce injured enterotoxigenic Escherichia coli or coliform bacteria (0.25 to 0.5 mg/liter) in the test system used; 50% lethal dose experiments in which mice were used showed that injured Y. enterocolitica cells were 20 times less virulent than uninjured control cells (3,300 and 160 CFU, respectively). This decrease in virulence was not related to reduced attachment to Henle 407 intestinal epithelial cells, but could be related to a loss of HeLa cell invasiveness. In contrast, injured S. typhimurium and enterotoxigenic E. coli cells lost their ability to attach to Henle cells. These data show that some enteropathogens and coliform bacteria differ in their sensitivities to chlorine injury and that the virulence determinants affected by chlorine may vary from one pathogen to another. 相似文献
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3.
The activities of nitrite reductase (EC 1.7.7.1) are 60–70% of wild-type activity in pigment-deficient leaves of the chloroplast-ribosomedeficient mutants albostrians (Hordeum vulgare) and iojap (Zea mays). The activity and apoprotein of nitrate reductase (EC 1.6.6.1.) are lacking in the barley mutant. Only very low activities of nitrate reductase can be extracted from leaves of the maize mutant. The molybdenum cofactor of nitrate reductase and xanthine dehydrogenase (EC 1.2.3.2) is present in maize and barley mutant plants. However, it is not inducible by nitrate in pigment-deficient leaves of albostrians. From these results we conclude: (i) Nitrite reductase (a chloroplast enzyme) is synthesized in the cytoplasm and does not need the presence of nitrate reductase for the induction and maintenance if its activity. (ii) The loss or low activity of nitrate reductase is a consequence of the inability of the mutants to accumulate the apoprotein of this enzyme. (iii) The chloroplasts influence the accumulation (i.e. most probably the synthesis) of the nonchloroplast enzyme, nitrate reductase. The accumulation of nitrate reductase needs a chloroplast factor which is not provided by mutant plastids blocked at an early stage of their development.Abbreviations CRM
cross-reacting material
- Mo-co
molybdenum cofactor
- NiR
nitrite reductase
- NR
nitrate reductase 相似文献
4.
W. Kreil Unger Hans Rundfeldt P. Metzner G. Schönberg K. Naumann Nover R. Schiemann H. Grimm P. Heriwig 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1965,35(8):374-376
Ohne Zusammenfassung 相似文献
5.
The inhibition of the growth of Yersinia enterocolitica by other gram-negative bacteria in mixed cultures at 32 degrees C was not the consequence of a depletion in essential nutrients, an unfavorable change in pH or oxygen tension or the production of toxic metabolic products. The inability of Y. enterocolitica to attain its potential maximum population in mixed cultures appeared instead to result from "metabolic crowding," which occurred when the faster-growing antagonistic organism reached stationary-phase density. Lowering the incubation temperature, a technique commonly used in "cold" enrichment for isolation of Y. enterocolitica, tended to equalize growth rates and thereby allowed Y. enterocolitica to achieve a higher population. 相似文献
6.
D A Schiemann 《Applied microbiology》1979,38(2):205-211
A total of 69 dyes were incorporated separately at different concentrations into an agar medium for evaluation of their effects on the quantitative recovery of five serotypes of Yersinia enterocolitica. One strain of Pseudomonas aeruginosa and one strain of Bacillus cereus were included for comparative purposes. Certain dyes were evaluated further for their selective properties with five additional serotypes of Y. enterocolitica, three strains of P. aeruginosa, and two of Engerobacter spp. Metanil yellow was the only dye which was tolerated bettr by Y. enterocolitica than by P. aeruginosa. Dye sensitivity was variable amond strains of the same serotype of Y. enterocolitica. In general, Y. enterocolitica showed a tolerance to dyes greater than that of gram-positive bacteria and similar to that of other gram-negative bacteria. 相似文献
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Elisabeth Schiemann Ramshorn Paula Hertwig E. Hoffmann Mühle Endemann H. J. Müller 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1954,24(7-8):243-244
Ohne Zusammenfassung 相似文献
9.
Jenny G. Parvani Amy J. Galliher-Beckley Barbara J. Schiemann William P. Schiemann 《Molecular biology of the cell》2013,24(21):3449-3459
Mammary tumorigenesis and epithelial–mesenchymal transition (EMT) programs cooperate in converting transforming growth factor-β (TGF-β) from a suppressor to a promoter of breast cancer metastasis. Although previous reports associated β1 and β3 integrins with TGF-β stimulation of EMT and metastasis, the functional interplay and plasticity exhibited by these adhesion molecules in shaping the oncogenic activities of TGF-β remain unknown. We demonstrate that inactivation of β1 integrin impairs TGF-β from stimulating the motility of normal and malignant mammary epithelial cells (MECs) and elicits robust compensatory expression of β3 integrin solely in malignant MECs, but not in their normal counterparts. Compensatory β3 integrin expression also 1) enhances the growth of malignant MECs in rigid and compliant three-dimensional organotypic cultures and 2) restores the induction of the EMT phenotypes by TGF-β. Of importance, compensatory expression of β3 integrin rescues the growth and pulmonary metastasis of β1 integrin–deficient 4T1 tumors in mice, a process that is prevented by genetic depletion or functional inactivation of β3 integrin. Collectively our findings demonstrate that inactivation of β1 integrin elicits metastatic progression via a β3 integrin–specific mechanism, indicating that dual β1 and β3 integrin targeting is necessary to alleviate metastatic disease in breast cancer patients. 相似文献
10.
Abstract A class of very potent nucleoside transport inhibitors is present in two molecular forms around physiological pH. We investigated whether the monoprotonated or the unionized species of these molecules binds to this camer protein with higher affinity. 相似文献