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Flagella enable bacteria to actively spread within the environment. A number of species possess two separate flagellar systems, where in most cases a primary polar flagellar system is supported by distinct secondary lateral flagella under appropriate conditions. Using functional fluorescence tagging on one of these species, Shewanella putrefaciens, as a model system, we explored how two different flagellar systems can exhibit efficient joint function. The S. putrefaciens secondary flagellar filaments are composed as a mixture of two highly homologous non-glycosylated flagellins, FlaA

The opportunistic pathogen Pseudomonas aeruginosa adapts to solid surfaces to enhance virulence and infect its host. Type IV pili (T4P), long and thin filaments that power surface-specific twitching motility, allow single cells to sense surfaces and control their direction of movement. T4P distribution is polarized to the sensing pole by the chemotaxis-like Chp system via a local positive feedback loop. However, how the initial spatially resolved mechanical signal is translated into T4P polarity is incompletely understood. Here, we demonstrate that the two Chp response regulators PilG and PilH enable dynamic cell polarization by antagonistically regulating T4P extension. By precisely quantifying the localization of fluorescent protein fusions, we show that phosphorylation of PilG by the histidine kinase ChpA controls PilG polarization. Although PilH is not strictly required for twitching reversals, it becomes activated upon phosphorylation and breaks the local positive feedback mechanism established by PilG, allowing forward-twitching cells to reverse. Chp thus uses a main output response regulator, PilG, to resolve mechanical signals in space and employs a second regulator, PilH, to break and respond when the signal changes. By identifying the molecular functions of two response regulators that dynamically control cell polarization, our work provides a rationale for the diversity of architectures often found in non-canonical chemotaxis systems.

ZusammenfassungMit der COVID-19-Pandemie stehen die Notaufnahmen als Schnittstelle der ambulanten und stationären Krankenversorgung vor einer großen Herausforderung. Die Dynamik der Pandemie zwang die Notfallversorgung des Universitätsklinikums Münster zu umfassenden Anpassungsprozessen, die in kürzester Zeit erfolgen mussten. Dazu gehörte die Etablierung einer ambulanten Coronateststelle und einer studentischen Telefonhotline. Innerklinisch wurden neue Isolationskapazitäten in der Notaufnahme sowie eine eigene COVID-19-Station eingerichtet. Der Patientenfluss wurde durch Flussdiagramme sowohl für den ambulanten als auch für den stationären Bereich neu geregelt. Das allgemeine und spezielle Notfallmanagement wurde für die reibungslose Versorgung COVID-19-positiver Patienten optimiert und das Personal in der Benutzung von Schutzausrüstung trainiert. Dieser Erlebnisbericht soll anderen Notaufnahmen in der Vorbereitung auf die COVID-19-Pandemie unterstützen.

Flagella-mediated motility, where propulsion is mediated by a rotating helical filament, is a very widespread and effective means of locomotion for numerous bacteria. Almost half of all species assemble their filament from more than one distinct building block, the flagellin. Here we show how bacteria may use different flagellins to build a filament best suited for different environments and that polarly flagellated bacteria employ a novel way of flagella-mediated motility.

The Palomar Fiber Nuller (PFN) is a rotating-baseline nulling interferometer that enables high-accuracy near-infrared (NIR) nulling observations with full azimuth coverage. To achieve NIR null-depth accuracies of several x 10-4, the PFN uses a common-mode optical system to provide a high degree of symmetry, single-mode-fiber beam combination to reduce sensitivity to pointing and wavefront errors, extreme adaptive optics to stabilize the fiber coupling and the cross-aperture fringe phase, rapid signal calibration and camera readout to minimize temporal effects, and a statistical null-depth fluctuation analysis to relax the phase stabilization requirement. Here we describe the PFN final design and performance, and provide a demonstration of faint-companion detection by means of nulling-baseline rotation, as originally envisioned for space-based nulling interferometry. Specifically, the Ks-band null-depth rotation curve measured on the spectroscopic binary eta Peg reflects both a secondary star 1.08 +/- 0.06 x 10-2 as bright as the primary, and a null-depth contribution of 4.8 +/- 1.6 x 10-4 due to the size of the primary star. With a 30 mas separation at the time, eta Peg B was well inside both the telescope diffraction-limited beam diameter (88 mas) and typical coronagraphic inner working angles. Finally, we discuss potential improvements that can enable a number of small-angle nulling observations on larger telescopes., 26 pages, 4 figures, accepted for publication in MNRAS

Significance Single cells across kingdoms of life explore, prey, escape, or congregate using surface-specific motility. Motile eukaryotic cells use chemotaxis to direct migration on surfaces. However, how bacteria control surface motility remains underexplored. Pseudomonas aeruginosa twitches on surfaces by successive extension and retraction of extracellular filaments called type IV pili. Here, we show that P. aeruginosa directs twitching by sensing mechanical input generated by type IV pili. The Chp sensory system performs spatially resolved mechanosensing by harnessing two response regulators with antagonistic functions. Our results demonstrate that sensory systems, whose input often remains elusive, can sense mechanical signals to actively steer motility. Furthermore, Chp establishes a signaling principle shared with higher-order organisms, identifying a conserved strategy to transduce spatially resolved signals., The opportunistic pathogen Pseudomonas aeruginosa explores surfaces using twitching motility powered by retractile extracellular filaments called type IV pili (T4P). Single cells twitch by sequential T4P extension, attachment, and retraction. How single cells coordinate T4P to efficiently navigate surfaces remains unclear. We demonstrate that P. aeruginosa actively directs twitching in the direction of mechanical input from T4P in a process called mechanotaxis. The Chp chemotaxis-like system controls the balance of forward and reverse twitching migration of single cells in response to the mechanical signal. Collisions between twitching cells stimulate reversals, but Chp mutants either always or never reverse. As a result, while wild-type cells colonize surfaces uniformly, collision-blind Chp mutants jam, demonstrating a function for mechanosensing in regulating group behavior. On surfaces, Chp senses T4P attachment at one pole, thereby sensing a spatially resolved signal. As a result, the Chp response regulators PilG and PilH control the polarization of the extension motor PilB. PilG stimulates polarization favoring forward migration, while PilH inhibits polarization, inducing reversal. Subcellular segregation of PilG and PilH efficiently orchestrates their antagonistic functions, ultimately enabling rapid reversals upon perturbations. The distinct localization of response regulators establishes a signaling landscape known as local excitation–global inhibition in higher-order organisms, identifying a conserved strategy to transduce spatially resolved signals.

Many bacterial species swim by rotating single polar helical flagella. Depending on the direction of rotation, they can swim forward or backward and change directions to move along chemical gradients but also to navigate their obstructed natural environment in soils, sediments, or mucus. When they get stuck, they naturally try to back out, but they can also resort to a radically different flagellar mode, which we discovered here. Using high-speed microscopy, we monitored the swimming behavior of the monopolarly flagellated species Shewanella putrefaciens with fluorescently labeled flagellar filaments at an agarose-glass interface. We show that, when a cell gets stuck, the polar flagellar filament executes a polymorphic change into a spiral-like form that wraps around the cell body in a spiral-like fashion and enables the cell to escape by a screw-like backward motion. Microscopy and modeling suggest that this propagation mode is triggered by an instability of the flagellum under reversal of the rotation and the applied torque. The switch is reversible and bacteria that have escaped the trap can return to their normal swimming mode by another reversal of motor direction. The screw-type flagellar arrangement enables a unique mode of propagation and, given the large number of polarly flagellated bacteria, we expect it to be a common and widespread escape or motility mode in complex and structured environments.

Bacteria swim in sequences of straight runs that are interrupted by turning events. They drive their swimming locomotion with the help of rotating helical flagella. Depending on the number of flagella and their arrangement across the cell body, different run-and-turn patterns can be observed. Here, we present fluorescence microscopy recordings showing that cells of the soil bacterium Pseudomonas putida that are decorated with a polar tuft of helical flagella, can alternate between two distinct swimming patterns. On the one hand, they can undergo a classical push-pull-push cycle that is well known from monopolarly flagellated bacteria but has not been reported for species with a polar bundle of multiple flagella. Alternatively, upon leaving the pulling mode, they can enter a third slow swimming phase, where they propel themselves with their helical bundle wrapped around the cell body. A theoretical estimate based on a random-walk model shows that the spreading of a population of swimmers is strongly enhanced when cycling through a sequence of pushing, pulling, and wrapped flagellar configurations as compared to the simple push-pull-push pattern.

A new high throughput screening method to characterise alloys used as gate metal of Metal/solid Electrolyte/Insulator/Semiconductor (MEIS) gas-sensors was developed. Samples with continuous gradients in alloy concentration for the system Pd 1-x-y Ni y Co y were analysed regarding H2 sensitivity. First results showed reduced poisoning effects of H2S for Ni concentrations between 4-11 at-% in Pd.

Homologs of the essential large tegument protein pUL36 of herpes simplex virus 1 are conserved throughout the Herpesviridae , complex with pUL37, and form part of the capsid-associated “inner” tegument. pUL36 is crucial for transport of the incoming capsid to and docking at the nuclear pore early after infection as well as for virion maturation in the cytoplasm. Its extreme C terminus is essential for pUL36 function interacting with pUL25 on nucleocapsids to start tegumentation (K. Coller, J. Lee, A. Ueda, and G. Smith, J. Virol. 81:11790-11797, 2007). However, controversy exists about the cellular compartment in which pUL36 is added to the nascent virus particle. We generated monospecific rabbit antisera against four different regions spanning most of pUL36 of the alphaherpesvirus pseudorabies virus (PrV). By immunofluorescence and immunoelectron microscopy, we then analyzed the intracellular location of pUL36 after transient expression and during PrV infection. While reactivities of all four sera were comparable, none of them showed specific intranuclear staining during PrV infection. In immunoelectron microscopy, neither of the sera stained primary enveloped virions in the perinuclear cleft, whereas extracellular mature virus particles were extensively labeled. However, transient expression of pUL36 alone resulted in partial localization to the nucleus, presumably mediated by nuclear localization signals (NLS) whose functionality was demonstrated by fusion of the putative NLS to green fluorescent protein (GFP) and GFP-tagged pUL25. Since PrV pUL36 can enter the nucleus when expressed in isolation, the NLS may be masked during infection. Thus, our studies show that during PrV infection pUL36 is not detectable in the nucleus or on primary enveloped virions, correlating with the notion that the tegument of mature virus particles, including pUL36, is acquired in the cytosol.

Computersysteme, wie wir sie heute kennen, passen sich typischerweise nicht an den Benutzer und dessen Situation an. Erste Beispiele von Systemen, die durch den Bezug zur Realwelt den Kontext des Benutzers einbeziehen, sind Navigationssysteme, die unter Berucksichtigung der Position eines Benutzers und der Verkehrslage Richtungsanweisungen geben konnen. Damit innovative kontextbezogene Anwendungen moglich werden, muss der Kontext, also der Zustand der Realwelt, durch Sensoren erfasst, in das Computersystem ubermittelt und dort in Form dynamischer Umgebungsmodelle den Anwendungen zur Verfugung gestellt werden. Der von der Deutschen Forschungsgemeinschaft geforderte und im Januar 2003 an der Universitat Stuttgart eingerichtete Sonderforschungsbereich SFB 627 ,,Umgebungsmodelle fur mobile kontextbezogene Anwendungen“ [22] ist ein interdisziplinarer Forschungsverbund von uber 30 Wissenschaftlern. Diese erforschen Methoden und Konzepte fur die Definition, Erstellung und Verwaltung von Umgebungsmodellen, durch die Anwendungen Zugriff auf Kontextinformationen erhalten.

Thirty‐four out of 64 faecal samples with adenovirus particles, as seen by electron microscopy, were found to contain adenovirus 40 or 41 by direct isolation and neutralization in Chang's conjunctival cells, mostly within one week. (Ad40 and 41 candidate viruses are serologically related.) 6 other adenovirus specics were isolated; 6 samples gave equivocal results, and 18 were negative. A genus‐specific ELISA with an antihexon coat yielded positive results in 40 out of 55 samples; the test failed to identify adenovirus antigen in 10 out of 17 specimens, which were found negative by culture. All of them were negative by immunfluorescence of inoculated Chang cell cultures. Hence the failures are probably due to insufficient amount of virus in the samples. The predominance of only two adenovirus species associated with gastroenteritis in children and the ease of cultivating and identifying them should help to elucidate their etiological significance.

A combined hybrid automatic repeat request (ARQ) error control and adaptive scheduling scheme is proposed for time-division multiple access/time-division duplex medium access control (MAC) protocols in wireless asynchronous transfer mode (ATM) networks. Specifically, with the aid of proper channel modeling, the performance of various error-control schemes is evaluated. Accordingly, type-II hybrid ARQ is chosen as the error recovery scheme to combat fading effects, while adaptive fair-queueing is designed to achieve a fair and efficient resource allocation in wireless channels. In particular, the weight of a connection used in the fair-queueing algorithm dynamically adapts in terms of varying channel conditions and the types of services. Various simulations are conducted in typical indoor wireless ATM networks. It is shown that the proposed scheme can achieve a high throughput and transfer reliability with minimized delay and cell loss rate when compared with the conventional MAC layer control.

Homologs of the UL25 gene product of herpes simplex virus 1 (HSV-1) are highly conserved among the Herpesviridae . However, their exact function during viral replication is unknown. Current evidence suggests that in the alphaherpesvirus pseudorabies virus (PrV) the capsid-associated pUL25 plays a role in primary envelopment of DNA-containing mature capsids at the inner nuclear membrane. In the absence of pUL25, capsids were found in close association with the inner nuclear membrane, but nuclear egress was not observed (B. G. Klupp, H. Granzow, G. M. Keil, and T. C. Mettenleiter, J. Virol. 80:6235-6246, 2006). In contrast, HSV-1 pUL25 has been assigned a role in stable packaging of viral genomes (N. Stow, J. Virol. 75:10755-10765, 2001). Despite these apparently divergent functions, we wanted to assess whether the high sequence homology translates into functional homology. Therefore, we first analyzed a newly constructed HSV-1 UL25 deletion mutant in our assay system and observed a similar phenotype as in PrV. In the nuclei of infected cells, numerous electron-dense C capsids were detected, whereas primary envelopment of these capsids did not ensue. In agreement with results from PrV, vesicles were observed in the perinuclear space. Since these data indicated functional homology, we analyzed the ability of pUL25 of HSV-1 to complement a PrV UL25 deletion mutant and vice versa. Whereas a HSV-1 pUL25-expressing cell line partially complemented the pUL25 defect in PrV, reciprocal complementation of a HSV-1 UL25 deletion mutant by PrV pUL25 was not observed. Thus, our data demonstrate overlapping, although not identical functions of these two conserved herpesvirus proteins, and point to a conserved functional role in herpes virion formation.

In den letzten Jahrzehnten haben sich zwei wesentlich verschiedene Netztechnologien herausgebildet: Telekommunikations- und Mobilkommunikationsnetze sowie Rechner- und Datennetze. Der Beitrag skizziert die sich gegenwärtig vollziehende Entwicklung einer Integration beider Technologien. Wesentliche Merkmale dieses Integrationsprozesses sind das Aufsetzen auf eingeführte Anschlussnetz- und Kernnetz-Infrastrukturen sowie der Übergang zu einer einheitlichen, auf dem Internet-Protokoll basierten Transporttechnik als Basis einer Plattform für ein sehr breites Spektrum von Diensten und Anwendungen. Diese Entwicklungen werden häufig unter dem Begriff „Next Generation Network“ (NGN) zusammengefasst, sind jedoch vielgestaltig und weisen eine größere Menge von Einzelaspekten auf. Nach einem kurzen Überblick über die wichtigsten Netztechnologien und Dienste wird eine Reihe von Herausforderungen an Netzkomponenten, Architekturen und Plattformen, Sicherheit, Netzmanagement und Netzorganisation diskutiert; auf den Aspekt der Dienst- und Netzgüte und dem damit einhergehenden Traffic Engineering wird etwas detaillierter eingegangen.

The reaction of peptide Gly-Ala-Phe with the alpha-dicarbonyl compounds glyoxal and methylglyoxal was studied under physiological conditions (pH=7.4, 37 degrees C). Using HPLC with UV and fluorescence detection, a rapid derivatization of the peptide and the concomitant formation of well-defined products were observed. The products, which showed characteristic UV absorbance (lambda(max)=320 to 340 nm) and fluorescence (lambda(ex)=330 to 340 nm, lambda(em)=395 to 405 nm), were identified by ESI-MS and NMR spectroscopic analysis as the N-terminally pyrazinone-modified peptides I (N-[2-(2-oxo-2H-pyrazin-1-yl)-propyl]-phenylalanine) and II (N-[2-(5-methyl-2-oxo-2H-pyrazin-1-yl)-propionyl]-phenylalanine). Model experiments revealed that the reactivity of the N-termini of peptides towards a derivatization by glyoxal is in the same order of magnitude as that of arginine, which generally is attributed as main target for alpha-dicarbonyl compounds in proteins. Incubation of insulin with glyoxal proved the protein-bound formation of pyrazinones, with the N-terminus of the B-chain as the main target. According to these results, we conclude that N-terminal pyrazinones represent a new type of advanced glycation end-products (AGEs) with significance for biological systems and foods.

Communication Networks migrate towards an infrastructure, which ischaracterized by seamless interoperation of heterogeneous subnetworks with different protocol architectures, network technologies, and services. The user will not be aware of this heterogeneity, but relies on a secure, reliable and efficient operation supporting his applications. To provide such a quality of service, communication networks have to meet stringent quality requirements with respect to

Like true DNA replicases, herpes simplex virus type 1 DNA polymerase is equipped with a proofreading 3'-5'-exonuclease. In order to assess the functional significance of conserved residues in the putative exonuclease domain, we introduced point mutations as well as deletions within and near the conserved motifs' exonuclease (Exo) I, II, and III of the DNA polymerase gene from a phosphonoacetic acid-resistant derivative of herpes simplex virus-1 strain ANG. We examined the catalytic activities of the partially purified enzymes after overexpression by recombinant baculovirus. Mutations of the motifs' Exo I (D368A, E370A) and Exo III (Y577F, D581A) yielded enzymes without detectable and severely impaired 3'-5'-exonuclease activities, respectively. Except for the Exo I mutations, all other Exo mutations examined affected both exonuclease and polymerization activities. Mutant enzymes D368A, E370A, Y557S, and D581A showed a significant ability to extend mispaired primer termini. Mutation Y557S resulted in a strong reduction of the 3'-5'-exonuclease activity and in a polymerase activity that was hyperresistant to phosphonoacetic acid. The results of the mutational analysis provide evidence for a tight linkage of polymerase and 3'-5'-exonuclease activity in the herpesviral enzyme.

In the Oriola depression of Southern Portugal near the town of Evora, field examinations revealed the presence of Tertiary sedimentary deposits that had the consistency of duricrusts. These duricrusts, occurring close to the land surface, were examined in the field as well as in the laboratory, with the objective of establishing their composition and formation. Micromorphological examinations showed that the duricrusts were composed of clasts of fine sand to fine gravel sizes cemented together by a matrix dominated by either palygorskite or carbonate. The matrix : clasts ratio varied from about 1 : 3 when the cement was carbonate, to 3 : 1 or higher when the matrix was palygorskite. Occasionally the ratio in the latter was even higher. The clasts consisted of quartz, feldspar, and some Mg-rich metamorphic minerals. The palygorskite matrix fibres were arranged in mats within which they had parallel orientation. The mats or ‘domains’, which had a length of 15–25 □m and a width of about 40 □m, showed random orientation. In analogy to the term ‘calcrete’ the term ‘palycrete’ is used for the palygorskite duricrusts. The palycrete, of an average thickness of 0.5 m, frequently rested directly on the Hercynian basement rocks, and was covered by a recent solum. In the B horizons of the solum, the palygorskite appeared to undergo recent weathering and transformation into smectite. The duricrusts were proposed to have formed by authigenic calcite or palygorskite, which filled the interstices between clastic particles that had been deposited on Hercynian basement rocks following their peneplanation in the early Tertiary. The proposed environment of deposition and formation was that of an intermittent playa-lake in a semi-arid, seasonal climate, where strong evaporative processes had been active. Alteration and weathering of the mafic minerals contained in some of the clasts, in addition to interstitial solutions rich in Si and Mg, had created the chemical environment required for palygorskite neoformation. From the state of weathering–disintegration of the palygorskite in the soils formed on the palycrete, it is inferred that the environment for palygorskite neoformation had ceased to exist after palycrete formation.

A proof is presented that the energy‐transfer ratios of the various elastic‐wave modes reflected and transmitted at a plane boundary between two media are symmetrical and equal to the product of the forward‐ and backward‐reflection coefficients. This relationship is shown to hold for several types of lossless boundary conditions at a solid‐solid interface.

Die vorliegende Arbeit stellt einen Beitrag zu der Frage dar, ob Trichomonaden durch direkte Einflusnahme auf Spermatozoen eine Fertilitatsstorung herbeifuhren konnen und ob Trichomonaden zur Storung einer Schwangerschaft fuhren konnen. Es ergab sich, das Trichomonas vaginalis und Trichomonas foetus, welche beide bakterienfrei gezuchtet wurden, in unterschiedlichem Mase Fructose und Glucose verbrauchen und damit auch pH-Anderungen im Sinne einer Sauerung erzeugen. Bei Kombination von Trichomonaden und Spermatozoen fand sich im allgemeinen ein additiver Verbrauchseffekt, jedoch verbrauchte Trichomonas foetus zusammen mit Sperma nicht mehr Glucose als Trichomonas foetus allein. Hieraus, ebenso wie aus der Tatsache, das Trichomonas vaginalis und Trichomonas foetus Glucose und das Trichomonas foetus Fructose verbraucht, ergibt sich die Moglichkeit der Beeintrachtigung des Energiestoffwechsels der Spermatozoen. Hinzu tritt als Schadigungseffekt die Milieuanderung und fraglich eine toxische Wirkung der Trichomonaden. Eine Schadigung der Spermatozoen durch Trichomonaden last sich auch durch die Anteile ortsbeweglicher und unbeweglicher Spermatozoen bei Gegenwart von Trichomonaden nachweisen. Fruchtwasseruntersuchungen ergaben, das bei vaginaler Fruchtwassergewinnung reichlich Trichomonaden nachzuweisen waren, welche indessen auf sekundarer Verunreinigung durch die Scheide beruhen konnen. An sich ist Fruchtwasser ein gutes Nahrmedium fur Trichomonaden. Aus Placenta- und Eihautteilen, aus Abortmaterial einschlieslich der Organe abortierter Feten konnten keine Trichomonaden gezuchtet werden. Wahrend somit eine Beeintrachtigung der Fertilitat durch Trichomonaden nicht auszuschliesen ist, besteht kein Anhalt fur das Vorliegen von Schwangerschaftsstorungen durch Trichomonaden.

The generation and reception of ultrasonic waves are discussed with the aim to improve existing wedge‐type angle probes used for nondestructive testing. A number of wedge materials are discussed, and it is shown that constructions using separate transducers for the generation of shear waves and reception of compressional waves in the wedge yield a higher echo‐transmission factor, larger signal‐to‐noise ratio, and a larger monitor signal than constructions using one transducer only.

The behaviour of products of local fields for lightlike distances is investigated. If a light cone expansion ofA(x)A(y) exists, then already the four point function carries the singularity arising in the expansion for (x−y)2→0. For a special class of field theories, discussed by S. Schlieder and E. Seiler, it is shown that the light cone expansion is possible.