Identification by Tn10 transposon mutagenesis of host factors involved in the biosynthesis of K99 fimbriae of Escherichia coli: Effect of LPS core mutations

Abstract Tn 10 transposon mutagenesis of Escherichia coli producing K99 fimbriae was carried out to identify host factors involved in regulation or biosynthesis of fimbriae. Two chromosomal mutants were obtained that showed a strongly reduced cell surface expression of K99 fimbriae upon colony blotting and ELISA. Analysis by inversed PCR and nucleotide sequencing showed that one mutant (EP14) contained the Tn 10 transposon in rfaQ , affecting theexpression of the rfaQGP gene cluster, whereas the other mutant (EP35) was affected in a, to date, unknown region of the genome. Immunoblotting analysis confirmed a Rd₁ type of LPS of mutant strain EP14. These findings for the first time indicated an effect of LPS core biosynthesis on the biogenesis of fimbriae at the cell surface. Preliminary experiments indicated that K99 major subunits, in contrast to K88 subunits, strongly bind LPS molecules.     

Über Koordinationsstörungen am Schildkrötenherzen

Zusammenfassung Durch mechanische Eingriffe, vor allem Zerrungen und Dehnungen, wird der Funktionszusammenhang zwischen den einzelnen Abteilungen des Herzens von Testudo graeca L. sehr leicht gelöst. Diese Störungen weichen nach wenigen Minuten von selbst, wenn die schädigende Ursache beseitigt wird.Im Tierkörper können solche Störungen, vorzugsweise durch einen starken Blutzufluß bewirkt werden. Dadurch werden die Herzabteilungen gedehnt, vor allem die empfindlichen Überleitungsgebilde. Ein stärkerer Blutzufluß zum Herzen wird aber durch die große Menge von Blutflüssigkeit vermieden, die sich normalerweise im Perikardialsack bei Testudo graeca L. befindet.Herrn Prof. Dr. Adolf Loewy, dem Leiter des Schweizerischen Forschungsinstituts, sage ich auch an dieser Stelle meinen ergebensten Dank für seine freundliche Aufnahme und tatkräftige Unterstützung.     

The allianceFimbristylidion dichotomae in Iraq

On silt deposits in river beds around Baghdad a new association, theCrypsidi-Fimbristylidetum was found, belonging to the allianceFimbristylidion dichotomae. As the period when river beds are bare, lasts about half a year, the life of this community is very short, but it appears anew every year. It produces about 80 g/m²/year dry wieght of biomass.     

Increase of free Mg<Superscript>2+</Superscript>in the skeletal muscle of chronic fatigue syndrome patients

In a previous study we evaluated muscle blood flow and muscle metabolism in patients diagnosed with chronic fatigue syndrome (CFS). To better understand muscle metabolism in CFS, we re-evaluated our data to calculate free Magnesium levels in skeletal muscle. Magnesium is an essential cofactor in a number of cell processes. A total of 20 CFS patients and 11 controls were evaluated. Phosphorus magnetic resonance spectroscopy from the medial gastrocnemius muscle was used to calculate free Mg²⁺ from the concentrations and chemical shifts of Pi, PCr, and beta ATP peaks. CFS patients had higher magnesium levels in their muscles relative to controls (0.47 + 0.07 vs 0.36 + 0.06 mM, P < 0.01), although there was no difference in the rate of phosphocreatine recovery in these subjects, as reported earlier. This finding was not associated with abnormal oxidative metabolism as measured by the rate of recovery of phosphocreatine after exercise. In summary, calculation of free Mg²⁺ levels from previous data showed CFS patients had higher resting free Mg²⁺ levels compared to sedentary controls.     

Characteristics of the rRNA synthesis taking place at low temperatures in wheat cultivars with varying degrees of frost hardiness

The characteristics and intensity of rRNA synthesis occurring at temperatures around freezing point were examined in connection with frost hardiness in wheat cultivars. The intensity of rRNA synthesis taking place near freezing point showed a close positive correlation with the critical temperature (LT₅₀) characteristic of the frost resistance of the varieties. The quantity of high MW precursors to rRNA appears to be heterogeneous in hardy and non hardy varieties at low temperatures and point primarily to an inhibition in the maturation processes of ribosomes in the final nuclease processing step in non-frosthardy varieties.     

Wanderung

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