University of Sussex

About: University of Sussex is a education organization based out in Brighton, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 17385 authors who have published 44685 publications receiving 2005538 citations.

Elucidating the Genetic Basis of Crystalline Biofilm Formation in Proteus mirabilis

Abstract: Proteus mirabilis forms extensive crystalline biofilms on urethral catheters that occlude urine flow and frequently complicate the management of long-term-catheterized patients. Here, using random transposon mutagenesis in conjunction with in vitro models of the catheterized urinary tract, we elucidate the mechanisms underpinning the formation of crystalline biofilms by P. mirabilis. Mutants identified as defective in blockage of urethral catheters had disruptions in genes involved in nitrogen metabolism and efflux systems but were unaffected in general growth, survival in bladder model systems, or the ability to elevate urinary pH. Imaging of biofilms directly on catheter surfaces, along with quantification of levels of encrustation and biomass, confirmed that the mutants were attenuated specifically in the ability to form crystalline biofilms compared with that of the wild type. However, the biofilm-deficient phenotype of these mutants was not due to deficiencies in attachment to catheter biomaterials, and defects in later stages of biofilm development were indicated. For one blocking-deficient mutant, the disrupted gene (encoding a putative multidrug efflux pump) was also found to be associated with susceptibility to fosfomycin, and loss of this system or general inhibition of efflux pumps increased sensitivity to this antibiotic. Furthermore, homologues of this system were found to be widely distributed among other common pathogens of the catheterized urinary tract. Overall, our findings provide fundamental new insight into crystalline biofilm formation by P. mirabilis, including the link between biofilm formation and antibiotic resistance in this organism, and indicate a potential role for efflux pump inhibitors in the treatment or prevention of P. mirabilis crystalline biofilms.

Becoming researchers: a sociocultural perspective on assessment, learning and the construction of identity in a professional doctorate

Abstract: The article reports on a small-scale in-depth research study investigating formative assessment enacted and theorised from a sociocultural perspective within a part-time Professional Doctorate in Education (EdD) programme in an English university. Going beyond its conventional conceptualisation within psychological and motivational frameworks, formative assessment here encouraged students to view their learning as entailing the development of identities as researchers. The research adopted a case study approach, drawing upon participant observation, discourse analysis of online discussion forum and email feedback, and two series of student interviews. Although the practice of formative assessment remains problematic, students' responses suggest the value of tutor feedback, including its ontological dimension. Given the wide-ranging backgrounds of the learners who participated in this study, our findings suggest the relevance of a sociocultural view of formative assessment for supporting a more diverse doctoral student population. This leads us to argue for doctoral supervision to be conceptualised more firmly as a pedagogic relation in which formative assessment has a key role.

Similarities within event clusters in autobiographical memory

Abstract: The organization of autobiographical memory is critical for both theory and application in many areas of psychology. Several theories of autobiographical memory state that memories are nested within higher-order cognitive structures. A procedure developed by Brown and Schopflocher is extended and used to explore similarities of various characteristics within these structures, which they call 'event clusters'. This phrase, event cluster, is used to describe events which cue one another. The purpose of this paper is to explore the similarities of events within the same cluster. We find that memories within a cluster are more likely to be similar with respect to clarity, emotion, importance, happiness and the estimated date in which they occurred compared with events from other clusters. Further, having nearly 1900 memories allows hypotheses about the relationships among clarity, emotion and importance to be examined in a way that is not possible with many other autobiographical data sets. Copyright © 2000 John Wiley & Sons, Ltd. Language: en

A spectrophotometric rapid kinetic study of reactions catalysed by coenzyme-B12-dependent ethanolamine ammonia-lyase.

Abstract: 1 Spectral changes during the transient states and the steady states of the reactions catalysed by the adenosylcobalamin-dependent ethanolamine ammonia-lyase with l-2-aminopropanol and 2-aminoethanol as substrates were followed by using a rapid-wavelength-scanning, stopped-flow spectrophotometer (800 spectra per second and each spectrum 340–560 nm). 2 During the steady state of the reaction with the ‘poor’ substrate, l-2-aminopropanol (kcat∼ 1 s−1), under conditions of V, the spectrum of the coenzyme closely resembled that of cob(II)alamin. With the ‘good’ substrate, 2-aminoethanol (kcat∼ 140 s−1), under the same conditions, the spectrum corresponded to a mixture of 58% cob(II)alamin and 42% cob(III)alamin. The latter may be either unchanged adenosylcobalamin or a coenzyme derivative with a covalent bond between a substrate carbon and the cobalt atom. The magnitude of a reported kinetic deuterium isotope effect favours the second possibility. There was no evidence for the presence of a cob(I)alamin intermediate. 3 The transient phases of the reactions were dependent on the order of mixing of reactants. When enzyme was placed in one syringe of the stopped-flow apparatus and coenzyme and substrate in the other, the cob(II)alamin intermediate formed slowly (first-order rate constants of about 5 s−1 with l-2-aminopropanol as substrate and about 2 s−1 with 2-aminoethanol). When the enzyme and coenzyme were placed in one syringe and the substrate in the other, the formation of the cob(II)alamin occurred much more rapidly (90 s−1 with l-2-aminopropanol and greater than 300 s−1 with 2-aminoethanol). It is concluded that binding of adenosylcobalamin to the enzyme is followed by a slow change in the conformation of the enzyme molecule to give a catalytically active species (there is no observable change in the spectrum of the coenzyme concommitant with this process). The formation of active holoenzyme is slow on the time scale of subsequent catalytic steps when 2-aminoethanol is the substrate. 4 The spectra of the intermediates formed in the reactions with both substrates, the rates of their formation and their lifetimes allowed a detailed kinetic analysis of the reactions in terms of a three-step mechanism involving binding of substrate, cob(II)alamin formation (k+2 step) and cob(II)alamin breakdown (k+3 step). In catalysis the difference between the substrates is expressed mainly in the k+3 step (240 s−1 and about 1 s−1 respectively for 2-aminoethanol and l-2-aminopropanol, the respective k+2 values being 336 s−1 and 90 s−1).

Where Do Foreign Direct Investment-Related Technology Spillovers Come From in Emerging Economies? An Exploration in Argentina in the 1990s

Abstract: Models underlying most research about foreign direct investment (FDI)-related spillovers suggest they originate in the centrally accumulated knowledge assets of multinational corporations (MNCs). From there a one-way 'pipeline' runs via a) international technology transfer to subsidiaries, b) 'leaks' into the host economy, c) varying degrees of absorption by domestic firms to d) those firms' productivity increases. We argue that this gives inadequate attention to knowledgecreating activities by MNC subsidiaries and domestic firms inside the host economy. These co-located and interacting activities are increasingly evident in knowledge-rich locations in advanced economies, reflecting location-specific advantages. We suggest here that such locally rooted and co-located knowledge creation may also lie between, but not necessarily causally connect, FDI and domestic firms' productivity growth in intermediate economies – as illustrated by the case of Argentina in the mid 1990s. Wider questions about policy are noted, with implications for future research highlighted.