We investigated the influence of regulatory and pathogenicity island-associated factors (Hha, RpoS, LuxS, EvgA, RfaH, and tRNA 5 Leu ) on biofilm formation by uropathogenic Escherichia coli (UPEC) strain 536. Only inactivation of rfaH, which encodes a transcriptional antiterminator, resulted in increased initial adhesion and biofilm formation by E. coli 536. rfaH inactivation in nonpathogenic E. coli K-12 isolate MG1655 resulted in the same phenotype. Transcriptome analysis of wild-type strain 536 and an rfaH mutant of this strain revealed that deletion of rfaH correlated with increased expression of flu orthologs. flu encodes antigen 43 (Ag43), which mediates autoaggregation and biofilm formation. We confirmed that deletion of rfaH leads to increased levels of flu and flu-like transcripts in E. coli K-12 and UPEC. Supporting the hypothesis that RfaH represses biofilm formation through reduction of the Ag43 level, the increased-biofilm phenotype of E. coli MG1655rfaH was reversed upon inactivation of flu. Deletion of the two flu orthologs, however, did not modify the behavior of mutant 536rfaH. Our results demonstrate that the strong initial adhesion and biofilm formation capacities of strain MG1655rfaH are mediated by both increased steady-state production of Ag43 and likely increased Ag43 presentation due to null rfaH-dependent lipopolysaccharide depletion. Although the roles of rfaH in the biofilm phenotype are different in UPEC strain 536 and K-12 strain MG1655, this study shows that RfaH, in addition to affecting the expression of bacterial virulence factors, also negatively controls expression and surface presentation of Ag43 and possibly another Ag43-independent factor(s) that mediates cell-cell interactions and biofilm formation.

The majority of Escherichia coli strains isolated from urinary tract infections have the potential to express multiple fimbriae. Two of the most common fimbrial adhesins are type 1 fimbriae and pyelonephritis-associated pili (Pap). Previous research has shown that induced, plasmid-based expression of a Pap regulator, papB, and its close homologues can prevent inversion of the fim switch controlling the expression of type 1 fimbriae. The aim of the present study was to determine if this cross-regulation occurs when PapB is expressed from its native promoter in the chromosome of E. coli K-12 and clinical isolates. The regulation was examined in three ways: (1) mutated alleles of the pap regulatory region, including papB and papI, that maintain the pap promoter in either the off or the on phase were exchanged into the chromosome of both E. coli K-12 and the clinical isolate E. coli CFT073, and the effect on type 1 fimbrial expression was measured; (2) type 1 fimbrial expression was determined using a novel fimS : : gfp + reporter system in mutants of the clinical isolate E. coli 536 in which combinations of complete fimbrial clusters had been deleted; (3) type 1 fimbrial expression was determined in a range of clinical isolates and compared with both the number of P clusters and their expression. All three approaches demonstrated that P expression represses type 1 fimbrial expression. Using a number of novel genetic approaches, this work extends the initial finding that PapB inhibits FimB recombination to the impact of this regulation in clinical isolates. INTRODUCTIONUrinary tract infections (UTIs) are common, affecting a large proportion of the population. It is estimated that 20 % of women develop a UTI in their lifetime, and antibiotic treatment results in approximately 110 000 prescriptions per million inhabitants per annum in Europe (Naber, 2000). Escherichia coli strains are the predominant cause of uncomplicated UTIs, responsible for between 60 and 80 % of the cases reported in the UK each year (Graham & Galloway, 2001). Many infections are asymptomatic, especially in the elderly (Nicolle, 2001), but others result in cystitis. If the infection ascends to the kidney, then pyelonephritis can occur. Such infections are a significant origin of Gramnegative sepsis.Fimbrial adhesins are important virulence factors that allow binding of the bacteria to specific receptors on epithelial cells of the urinary tract. The two adhesins most commonly associated with UTI are type 1 fimbriae, and pyelonephritisassociated pili (Pap) and Pap-related fimbriae (Prf); the last two are collectively termed P fimbriae in this study. Type 1 fimbriae mediate binding to a-D-mannose-containing receptors and extracellular matrix components, whereas P fimbriae bind to glycoreceptors containing the aGal(1-4)bGal moiety (Lindberg et al., 1984). Although type 1 fimbriae are common to the majority of E. coli isolates, the FimH adhesin has been shown to be important in a mouse model of UTI, and a degranulation response to the fimbriae is asso...

The resurrection plant Myrothamnus flabellifolia has the ability to recover from repeated prolonged and extreme desiccation cycles. During the dry state the inner walls of the xylem vessels seemed to be covered, at least partly, by a lipid film as shown by Sudan III and Nile Red staining. The lipid film apparently functioned as an ' internal cuticle ' which prevented the adjacent parenchyma ray cells from complete water loss. The hydrophobic nature of the inner xylem walls was supported by the finding that benzene ascended as rapidly as water in the xylem of dry Myrothamnus branches. On watering, numerous lipid bodies were found in the water-conducting vessels, presumably formed from the lipid film and\or from lipids excreted from the adjacent living cells into the vessels. The presence of lipid bodies within the vessels, as well as the hydrophobic properties of the inner xylem walls, could explain the finding that the xylem pressure of hydrated, well watered plants (measured both under laboratory and field conditions with the xylem pressure probe) never dropped below c. k0.3 MPa and that cavitation occurred frequently at low negative xylem pressure values (k0.05 to k0.15 MPa). The xylem pressure of M. flabellifolia responded rapidly and strongly to changes in relative humidity and temperature, but less obviously to changes in irradiance (which varied between 10 and c. 4000 µmol m −# s −" ). The morphological position of the stomata in the leaves could explain the extremely weak and slow response of the xylem pressure of this resurrection plant to illumination changes. Stomata were most abundant in the furrows, and were thus protected from direct sunlight. Simultaneous measurements of the cell turgor pressure in the leaf epidermal cells (made by using the cell turgor pressure probe) revealed that the xylem and the cell turgor pressure dropped in a ratio of 1 : 0.7 on changes in the environmental parameters, indicating a quite close hydraulic connection and, thus, water equilibrium between the xylem and cellular compartments. An increase in irradiance of c. 700 µmol m −# s −" resulted in a turgor pressure decrease from 0.63 to 0.48 MPa. Correspondingly, the cell osmotic pressure increased from 1.03 to 1.22 MPa. From these values and by assuming water equilibrium, the osmotic pressure of the xylem sap was estimated to be 0.25-0.4 MPa. This value seems to be fairly high but may, however, be explained by the reduction of the water volume within the vessels due to the floating lipid bodies.

Von "schlauen FÜKSEN" und "alten Hasen" SchülerInnen unterrichten SeniorInnen "Gehen Sie mit der Maus auf den Menüpunkt ‚Datei' und dann auf 'Speichern unter'" . So lautet die mögliche Anweisung einer jungen Lehrerin oder eines jungen Lehrers im Fach "Computer für Anfänger". In anderen Klassenräumen werden Fremdsprachen gesprochen, der Umgang mit neuen Medien gelehrt oder das Gedächtnis trainiert. So oder ähnlich gestaltet sich der Schulalltag für die TeilnehmerInnen des FUKS-Projektes am Geschwister-Scholl-Gymnasium in Pulheim.Das FUKS-Projekt ist ein Generationen übergreifendes Projekt, bei dem SchülerInnen ab der 9. Klasse in die Rolle der LehrerInnen schlüpfen und Senio-rInnen ab dem 50. Lebensjahr wieder die "Schulbank drücken". Die Buchstaben des Namens "FUKS" stehen hierbei für "Forschen", "Unterrichten", "Kennlernen" und "Staunen". Die SchülerInnen unterrichten im Team die SeniorInnen in Englisch, Französisch oder anderen Fremdsprachen, im Umgang mit dem Computer oder dem Handy und in vielem mehr, je nach Interesse und Fähigkeiten der jugendlichen LehrerInnen. Selbst die körperliche Fitness kommt nicht zu kurz, denn auch ein Gymnastikkurs steht auf dem "Stundenplan". Und auf Wunsch der SeniorInnen wurde auch der Kurs "Gedächtnistraining" ein fester Bestandteil des Programms.Das FUKS-Projekt konkurriert dabei nicht mit der Volkshochschule. Es wendet sich an SeniorInnen, die ohne Zeitdruck lernen wollen, kein Zertifikat anstreben und den Kontakt zur Jugend suchen. In lockerer Atmosphäre kann früher Gelerntes aufgefrischt und/oder etwas Neues ausprobiert werden. Das Miteinander von "Jung und Alt" ist hierbei genauso wichtig wie die Wissensvermittlung.Der Unterricht findet immer freitags in der Zeit zwischen 14.00 und 17.00 Uhr in den Räumen des Gymnasiums statt. Drei Zeiteinheiten stehen für den Un-terricht zur Verfügung, sodass die Senio-rInnen die Möglichkeit haben, drei verschiedene Kurse zu belegen. Umgekehrt können die SchülerInnen bis zu drei verschiedene Kurse am Nachmittag anbieten. In den ausgedehnten Pausen besteht für alle TeilnehmerInnen des Projektes in der Cafeteria die Möglichkeit, sich zu treffen und auszutauschen. Vielleicht müssen ja auch noch die "Hausaufgaben" erledigt werden.Zurzeit befindet sich das Projekt im sechsten "FUKS-Schuljahr", derzeit nehmen etwa 50 SchülerInnen sowie rund 100 SeniorInnen am Projekt teil. Wie eine typische Unterrichtsstunde aussieht, beschreibt Nora Schnorrenberg aus der Klasse 8c: "Ich selbst habe mich letztes und auch dieses Jahr für Gedächtnistraining entschieden, weil ich in diesem Bereich am meisten von meinem Wissen weitergeben kann. Wenn ich dann freitags um 13.25 Uhr Schule aushabe, gehe ich in unsere Cafeteria, um mir ein Brötchen und eine Flasche Cola zu holen, die uns von den FUKS-Koordinatoren jeden Freitag bereitgestellt werden. Anschließend begebe ich mich in den Raum, in dem um 14.00 Uhr mein Unterricht beginnt. Ich stelle dort die Tische um, damit wir alle etwas enger zusammensitzen und uns besser verstehen. Wenn dann die Stunde beginnt und all...