The bat and the ball; or, Negative evidence, a farce in one act,

Mode of access: Internet.

Generalization by symbolic abstraction in cascaded recurrent networks

Generalization performance in recurrent neural networks is enhanced by cascading several networks. By discretizing abstractions induced in one network, other networks can operate on a coarse symbolic level with increased performance on sparse and structural prediction tasks. The level of systematicity exhibited by the cascade of recurrent networks is assessed on the basis of three language domains. (C) 2004 Elsevier B.V. All rights reserved.

Reconciling paleodistribution models and comparative phylogeography in the Wet Tropics rainforest land snail Gnarosophia bellendenkerensis (Brazier 1875)

Comparative phylogeography has proved useful for investigating biological responses to past climate change and is strongest when combined with extrinsic hypotheses derived from the fossil record or geology. However, the rarity of species with sufficient, spatially explicit fossil evidence restricts the application of this method. Here, we develop an alternative approach in which spatial models of predicted species distributions under serial paleoclimates are compared with a molecular phylogeography, in this case for a snail endemic to the rainforests of North Queensland, Australia. We also compare the phylogeography of the snail to those from several endemic vertebrates and use consilience across all of these approaches to enhance biogeographical inference for this rainforest fauna. The snail mtDNA phylogeography is consistent with predictions from paleoclimate modeling in relation to the location and size of climatic refugia through the late Pleistocene-Holocene and broad patterns of extinction and recolonization. There is general agreement between quantitative estimates of population expansion from sequence data (using likelihood and coalescent methods) vs. distributional modeling. The snail phylogeography represents a composite of both common and idiosyncratic patterns seen among vertebrates, reflecting the geographically finer scale of persistence and subdivision in the snail. In general, this multifaceted approach, combining spatially explicit paleoclimatological models and comparative phylogeography, provides a powerful approach to locating historical refugia and understanding species' responses to them.

Attribution and reciprocity in a simulated labor market: An experimental investigation

While papers such as Akerlof and Yellen (1990) and Rabin (1993) argue that psychological considerations such as fairness and reciprocity are important in individual decision-making, there is little explicit empirical evidence of reciprocal altruism in economic environments. This paper tests whether attribution of volition in choosing a wage has a significant effect on subsequent costly effort provision. An experiment was conducted in which subjects are first randomly divided into groups of employers and employees. Wages were selected and employees asked to choose an effort level, where increased effort is costly to the employee, but highly beneficial to the employer. The wage-determination process was common knowledge and wages were chosen either by the employer or by an external process. There is evidence for both distributional concerns and reciprocal altruism. The slope of the effort/wage profile is clearly positive in all cases, but is significantly higher when wages are chosen by the employer, offering support for the hypothesis of reciprocity. There are implications for models of utility and a critique of some current models is presented.

L1 transfer in the acquisition of manner and path in Spanish by native speakers of English

In this article the authors argue that L1 transfer from English is not only important in the early stages of L2 acquisition of Spanish, but remains influential in later stages if there is not enough positive evidence for the learners to progress in their development (Lefebvre, White, & Jourdan, 2006). The findings are based on analyses of path and manner of movement in stories told by British students of Spanish (N = 68) of three different proficiency levels. Verbs that conflate motion and path, on the one hand, are mastered early, possibly because the existence of Latinate path verbs, such as enter and ascend in English, facilitate their early acquisition by British learners of Spanish. Contrary to the findings of Cadierno (2004) and Cadierno and Ruiz (2006), the encoding of manner, in particular in boundary crossing contexts, seems to pose enormous difficulties, even among students who had been abroad on a placement in a Spanish-speaking country prior to the data collection. An analysis of the frequency of manner verbs in Spanish corpora shows that one of the key reasons why students struggle with manner is that manner verbs are so infrequent in Spanish. The authors claim that scarce positive evidence in the language exposed to and little or no negative evidence are responsible for the long-lasting effect of transfer on the expression of manner.

The Acquisition of Aspect in L2 Portuguese & Spanish: Exploring Native/Non-Native Performance Differences.

This study investigates the possibility of native-like ultimate attainment by analyzing L2 knowledge of aspect as seen in the Preterit/Imperfect contrast of highly successful English L2 learners of Portuguese and Spanish. Building on innovative work by Montrul & Slabakova (2003) and Slabakova & Montrul (2003), we test knowledge of semantic entailments associated with the acquisition of [+/- perfective] features checked in higher AspP. Additionally, we investigate the possibility of a specific pattern of associated target-deviant L2 performance. We hypothesize that L2 performance can be affected by explicit positive evidence (pedagogical rules) despite otherwise demonstrable native-like competence. Indeed, the data reveal a pattern of target-deviant performance noted only in three specific contexts, all of which can be linked to traditional instruction: (a) with particular stative verbs not used in the Preterit (b) when preceded by certain adverbial phrases (e.g.,siempre) and (c) so-called semantic shifting verbs (e.g., sabía vs. supe).

Espaços especiais em Natal (moradia e meio ambiente): um necessário diálogo entre direitos e espaços na perspectiva de proteção aos direitos fundamentais na cidade contemporânea

Some protected special spaces on behalf of fundamental rights to the environment and the housing at the city of Natal are fragile by facing actions and attempts to suppress and changing (or omission in the implementation) of standards in furtherance of those rights at the local level, which seems to reflect a situation that goes beyond the context of the city. Based on integrated approach of the housing rights and the environment and its protection of special spaces on the field of fundamental rights, the thesis seeks to understand the weaknesses that affect the legal state duty under the realization/implementation of fundamental rights to the environment and housing in cities, focusing on the issues of flexibility of the founding legislation of special spaces to the detriment of the attributes they protected and the lack of implementation of the legal system that allows their effectiveness. So, it looks initially to understand the environment and housing rights and their special protected areas in the brazilian legal system, looking forward the evolution of its legal protection, as well as the weaknesses that emerge in the field of their effectiveness. Analyzing the trajectory of the environment and housing rights and their special protected areas in Natal, considering its standards, attributes, protection indicators, weaknesses and negative evidence within its legal protections and their enforcement by state entity, this thesis proposes to verify the existence of forms to confronting the weaknesses founded in the maintenance of legal protection and its implementation. At this point it discusses the legal basis and safeguard instruments of protection, especially within the juridical field, as part of a (re)discussion about issues of legislative and administrative discretion in the face of objective legal state duty to realization/implementation of fundamental rights in the urban space. With all these issues together the thesis does not ignore the scenario where the dividing line between public and private (economic) are becoming ever more tenuous in the field of state action and where the city stands as a special commodity to the reproduction of real estate, according to the interests of capitalist logic

Positivity violation for the lattice Landau gluon propagator

We present explicit numerical evidence of reflection-positivity violation for the lattice Landau gluon propagator in three-dimensional pure SU(2) gauge theory. We use data obtained at very large lattice volumes (V = 80(3), 140(3)) and for three different lattice couplings in the scaling region (beta = 4.2, 5.0, 6.0). In particular, we observe a clear oscillatory pattern in the real-space propagator C(t). We also verify that the (real-space) data show good scaling in the range t is an element of[0, 3]fm and can be fitted using a Gribov-like form. The violation of positivity is in contradiction with a stable-particle interpretation of the associated field theory and may be viewed as a manifestation of confinement.

Oscillatory genetic circuits: new designs and mathematical models

Introduction and motivation: A wide variety of organisms have developed in-ternal biomolecular clocks in order to adapt to cyclic changes of the environment. Clock operation involves genetic networks. These genetic networks have to be mod¬eled in order to understand the underlying mechanism of oscillations and to design new synthetic cellular clocks. This doctoral thesis has resulted in two contributions to the fields of genetic clocks and systems and synthetic biology, generally. The first contribution is a new genetic circuit model that exhibits an oscillatory behav¬ior through catalytic RNA molecules. The second and major contribution is a new genetic circuit model demonstrating that a repressor molecule acting on the positive feedback of a self-activating gene produces reliable oscillations. First contribution: A new model of a synthetic genetic oscillator based on a typical two-gene motif with one positive and one negative feedback loop is pre¬sented. The originality is that the repressor is a catalytic RNA molecule rather than a protein or a non-catalytic RNA molecule. This catalytic RNA is a ribozyme that acts post-transcriptionally by binding to and cleaving target mRNA molecules. This genetic clock involves just two genes, a mRNA and an activator protein, apart from the ribozyme. Parameter values that produce a circadian period in both determin¬istic and stochastic simulations have been chosen as an example of clock operation. The effects of the stochastic fluctuations are quantified by a period histogram and autocorrelation function. The conclusion is that catalytic RNA molecules can act as repressor proteins and simplify the design of genetic oscillators. Second and major contribution: It is demonstrated that a self-activating gene in conjunction with a simple negative interaction can easily produce robust matically validated. This model is comprised of two clearly distinct parts. The first is a positive feedback created by a protein that binds to the promoter of its own gene and activates the transcription. The second is a negative interaction in which a repressor molecule prevents this protein from binding to its promoter. A stochastic study shows that the system is robust to noise. A deterministic study identifies that the oscillator dynamics are mainly driven by two types of biomolecules: the protein, and the complex formed by the repressor and this protein. The main conclusion of this study is that a simple and usual negative interaction, such as degradation, se¬questration or inhibition, acting on the positive transcriptional feedback of a single gene is a sufficient condition to produce reliable oscillations. One gene is enough and the positive transcriptional feedback signal does not need to activate a second repressor gene. At the genetic level, this means that an explicit negative feedback loop is not necessary. Unlike many genetic oscillators, this model needs neither cooperative binding reactions nor the formation of protein multimers. Applications and future research directions: Recently, RNA molecules have been found to play many new catalytic roles. The first oscillatory genetic model proposed in this thesis uses ribozymes as repressor molecules. This could provide new synthetic biology design principles and a better understanding of cel¬lular clocks regulated by RNA molecules. The second genetic model proposed here involves only a repression acting on a self-activating gene and produces robust oscil¬lations. Unlike current two-gene oscillators, this model surprisingly does not require a second repressor gene. This result could help to clarify the design principles of cellular clocks and constitute a new efficient tool for engineering synthetic genetic oscillators. Possible follow-on research directions are: validate models in vivo and in vitro, research the potential of second model as a genetic memory, investigate new genetic oscillators regulated by non-coding RNAs and design a biosensor of positive feedbacks in genetic networks based on the operation of the second model Resumen Introduccion y motivacion: Una amplia variedad de organismos han desarro-llado relojes biomoleculares internos con el fin de adaptarse a los cambios ciclicos del entorno. El funcionamiento de estos relojes involucra redes geneticas. El mo delado de estas redes geneticas es esencial tanto para entender los mecanismos que producen las oscilaciones como para diseiiar nuevos circuitos sinteticos en celulas. Esta tesis doctoral ha dado lugar a dos contribuciones dentro de los campos de los circuitos geneticos en particular, y biologia de sistemas y sintetica en general. La primera contribucion es un nuevo modelo de circuito genetico que muestra un comportamiento oscilatorio usando moleculas de ARN cataliticas. La segunda y principal contribucion es un nuevo modelo de circuito genetico que demuestra que una molecula represora actuando sobre el lazo de un gen auto-activado produce oscilaciones robustas. Primera contribucion: Es un nuevo modelo de oscilador genetico sintetico basado en una tipica red genetica compuesta por dos genes con dos lazos de retroa-limentacion, uno positivo y otro negativo. La novedad de este modelo es que el represor es una molecula de ARN catalftica, en lugar de una protefna o una molecula de ARN no-catalitica. Este ARN catalitico es una ribozima que actua despues de la transcription genetica uniendose y cortando moleculas de ARN mensajero (ARNm). Este reloj genetico involucra solo dos genes, un ARNm y una proteina activadora, aparte de la ribozima. Como ejemplo de funcionamiento, se han escogido valores de los parametros que producen oscilaciones con periodo circadiano (24 horas) tanto en simulaciones deterministas como estocasticas. El efecto de las fluctuaciones es-tocasticas ha sido cuantificado mediante un histograma del periodo y la función de auto-correlacion. La conclusion es que las moleculas de ARN con propiedades cataliticas pueden jugar el misnio papel que las protemas represoras, y por lo tanto, simplificar el diseno de los osciladores geneticos. Segunda y principal contribucion: Es un nuevo modelo de oscilador genetico que demuestra que un gen auto-activado junto con una simple interaction negativa puede producir oscilaciones robustas. Este modelo ha sido estudiado y validado matematicamente. El modelo esta compuesto de dos partes bien diferenciadas. La primera parte es un lazo de retroalimentacion positiva creado por una proteina que se une al promotor de su propio gen activando la transcription. La segunda parte es una interaction negativa en la que una molecula represora evita la union de la proteina con el promotor. Un estudio estocastico muestra que el sistema es robusto al ruido. Un estudio determinista muestra que la dinamica del sistema es debida principalmente a dos tipos de biomoleculas: la proteina, y el complejo formado por el represor y esta proteina. La conclusion principal de este estudio es que una simple y usual interaction negativa, tal como una degradation, un secuestro o una inhibition, actuando sobre el lazo de retroalimentacion positiva de un solo gen es una condition suficiente para producir oscilaciones robustas. Un gen es suficiente y el lazo de retroalimentacion positiva no necesita activar a un segundo gen represor, tal y como ocurre en los relojes actuales con dos genes. Esto significa que a nivel genetico un lazo de retroalimentacion negativa no es necesario de forma explicita. Ademas, este modelo no necesita reacciones cooperativas ni la formation de multimeros proteicos, al contrario que en muchos osciladores geneticos. Aplicaciones y futuras lineas de investigacion: En los liltimos anos, se han descubierto muchas moleculas de ARN con capacidad catalitica. El primer modelo de oscilador genetico propuesto en esta tesis usa ribozimas como moleculas repre¬soras. Esto podria proporcionar nuevos principios de diseno en biologia sintetica y una mejor comprension de los relojes celulares regulados por moleculas de ARN. El segundo modelo de oscilador genetico propuesto aqui involucra solo una represion actuando sobre un gen auto-activado y produce oscilaciones robustas. Sorprendente-mente, un segundo gen represor no es necesario al contrario que en los bien conocidos osciladores con dos genes. Este resultado podria ayudar a clarificar los principios de diseno de los relojes celulares naturales y constituir una nueva y eficiente he-rramienta para crear osciladores geneticos sinteticos. Algunas de las futuras lineas de investigation abiertas tras esta tesis son: (1) la validation in vivo e in vitro de ambos modelos, (2) el estudio del potential del segundo modelo como circuito base para la construction de una memoria genetica, (3) el estudio de nuevos osciladores geneticos regulados por ARN no codificante y, por ultimo, (4) el rediseno del se¬gundo modelo de oscilador genetico para su uso como biosensor capaz de detectar genes auto-activados en redes geneticas.

A bizonyosságfüggvények elméletének alkalmazása a pénzügyi kimutatások ellenőrzésében (The application of the theory of belief functions in the audit of financial statements)

A könyvvizsgálati kockázat a téves auditjelentés kiadásának kockázata olyan esetekben, amikor a beszámoló lényeges hibás állítást tartalmaz. Ez a kockázat indirekt módon a hitelintézetek és pénzügyi vállalkozások működésében is megjelenik azokban az esetekben, amikor a lényeges hibás állítást a finanszírozott vállalkozás auditált beszámolója tartalmazza, amelynek az alapján finanszírozási döntést hoznak, vagy a finanszírozás folytatásáról a beszámolóban szereplő, hibás információkból számított hitelkovenánsok alapján döntenek. A könyvvizsgálat kockázatában a vizsgált gazdálkodó üzleti kockázatai tükröződnek vissza, ezért a kockázat felmérése és az ellenőrzés ennek alapján való megtervezése, majd végrehajtása kulcsfontosságú. Jelen tanulmány – kapcsolódva a Hitelintézeti Szemle 2011. évi 4. számához – szintén a kockázat és bizonytalanság témakörét tárgyalja, pontosabban ennek egy gyakorlati vetületét: a bizonyosságfüggvények (belief functions) alkalmazását a könyvvizsgálatban; mindezt a teljesség és a tankönyvszerű rendszerfelépítés igénye nélkül. A módszer ugyanis hazánkban szinte ismeretlen, nemzetközi viszonylatban viszont empirikus kutatásban is rámutattak már az alkalmazás lehetséges előnyeire a hagyományos valószínűségelméleten alapuló számszerű kockázatbecslésekkel szemben. Eszerint a bizonyosságfüggvények jobban reprezentálják a könyvvizsgálóknak a kockázatról alkotott képét, mint a valószínűségek, mert – szemben a hagyományos modellel – nem két, hanem három állapotot kezelnek: a pozitív bizonyíték létezését, a negatív bizonyíték létezését és a bizonyíték hiányának esetét. _______ Audit risk is the risk that the auditor expresses an inappropriate audit opinion when the fi nancial statements are materially misstated. This kind of risk indirectly appears in the fi nancial statements of fi nancial institutions, when the material misstatement is in the fi nanced entity’s statements that serve as a basis for lending decisions or when the decision is made based upon credit covenants calculated from misstated information. The risks of the audit process refl ect the business risks of the auditee, so the assessment of risks, and further the planning and performance of the audit based on it is of key importance. The current study – connecting to No 4 2011 of Hitelintézeti Szemle – also discusses the topic of risk and uncertainty, or to be more precise a practical implementation of the aforementioned: the application of belief functions in the fi eld of external audit. All this without the aim of achieving completeness or textbook-like scrutiny in building up the theory. While the formalism is virtually unknown in Hungary, on the international scene empirical studies pointed out the possible advantages of the application of the method in contrast to risk assessments based on the traditional theory of probability. Accordingly, belief functions provide a better representation of auditors’ perception of risk, as in contrast to the traditional model, belief functions deal with three rather than two states: the existence of supportive evidence, that of negative evidence and the lack of evidence.

(Table 1) Radiocarbon results from this study

The Indonesian Arc represents the subduction of the Indian-Australian plate beneath Asia. It has been the scene of catastrophic tectonic activity, including the recent 2004 M=9.1 Aceh earthquake and resulting Indian Ocean tsunami. We have dated planktonic forams associated with historic tephras (Tambora, 1815 and Krakatau, 1883) in marine sediment cores to determine radiocarbon reservoir ages for 2 locations along the arc. Our best estimates for 19th century regional reservoir corrections (DeltaR) are +90 ± 40 yr for surface-dwelling species and +220 ± 40 yr for mixed planktic assemblages containing some upper thermocline species, but scatter in the data suggests that past surface reservoir ages may have varied by about ±100 yr. We used the results of this study to investigate a proposed very large AD 535 eruption at or near Krakatau. We find no evidence for ash from such an eruption, and although this is negative evidence, we consider it sufficiently strong to rule out any possibility that one took place.

Espaços especiais em Natal (moradia e meio ambiente): um necessário diálogo entre direitos e espaços na perspectiva de proteção aos direitos fundamentais na cidade contemporânea

Some protected special spaces on behalf of fundamental rights to the environment and the housing at the city of Natal are fragile by facing actions and attempts to suppress and changing (or omission in the implementation) of standards in furtherance of those rights at the local level, which seems to reflect a situation that goes beyond the context of the city. Based on integrated approach of the housing rights and the environment and its protection of special spaces on the field of fundamental rights, the thesis seeks to understand the weaknesses that affect the legal state duty under the realization/implementation of fundamental rights to the environment and housing in cities, focusing on the issues of flexibility of the founding legislation of special spaces to the detriment of the attributes they protected and the lack of implementation of the legal system that allows their effectiveness. So, it looks initially to understand the environment and housing rights and their special protected areas in the brazilian legal system, looking forward the evolution of its legal protection, as well as the weaknesses that emerge in the field of their effectiveness. Analyzing the trajectory of the environment and housing rights and their special protected areas in Natal, considering its standards, attributes, protection indicators, weaknesses and negative evidence within its legal protections and their enforcement by state entity, this thesis proposes to verify the existence of forms to confronting the weaknesses founded in the maintenance of legal protection and its implementation. At this point it discusses the legal basis and safeguard instruments of protection, especially within the juridical field, as part of a (re)discussion about issues of legislative and administrative discretion in the face of objective legal state duty to realization/implementation of fundamental rights in the urban space. With all these issues together the thesis does not ignore the scenario where the dividing line between public and private (economic) are becoming ever more tenuous in the field of state action and where the city stands as a special commodity to the reproduction of real estate, according to the interests of capitalist logic

Espaços especiais em Natal (moradia e meio ambiente): um necessário diálogo entre direitos e espaços na perspectiva de proteção aos direitos fundamentais na cidade contemporânea

Some protected special spaces on behalf of fundamental rights to the environment and the housing at the city of Natal are fragile by facing actions and attempts to suppress and changing (or omission in the implementation) of standards in furtherance of those rights at the local level, which seems to reflect a situation that goes beyond the context of the city. Based on integrated approach of the housing rights and the environment and its protection of special spaces on the field of fundamental rights, the thesis seeks to understand the weaknesses that affect the legal state duty under the realization/implementation of fundamental rights to the environment and housing in cities, focusing on the issues of flexibility of the founding legislation of special spaces to the detriment of the attributes they protected and the lack of implementation of the legal system that allows their effectiveness. So, it looks initially to understand the environment and housing rights and their special protected areas in the brazilian legal system, looking forward the evolution of its legal protection, as well as the weaknesses that emerge in the field of their effectiveness. Analyzing the trajectory of the environment and housing rights and their special protected areas in Natal, considering its standards, attributes, protection indicators, weaknesses and negative evidence within its legal protections and their enforcement by state entity, this thesis proposes to verify the existence of forms to confronting the weaknesses founded in the maintenance of legal protection and its implementation. At this point it discusses the legal basis and safeguard instruments of protection, especially within the juridical field, as part of a (re)discussion about issues of legislative and administrative discretion in the face of objective legal state duty to realization/implementation of fundamental rights in the urban space. With all these issues together the thesis does not ignore the scenario where the dividing line between public and private (economic) are becoming ever more tenuous in the field of state action and where the city stands as a special commodity to the reproduction of real estate, according to the interests of capitalist logic

Gli eventi avversi che possono insorgere nel trattamento riabilitativo volto al recupero della deambulazione nel paziente con Stroke: a Scoping Review

Background: I trattamenti volti al recupero della deambulazione nel paziente post stroke sono ampiamente declinati in letteratura, ma vi sono tanti interrogativi per quanto riguarda gli eventi avversi che possono intercorrere in neuroriabilitazione. Dato l’ampio spettro di opzioni terapeutiche in questo ambito, innanzitutto, è utile comprendere quali trattamenti si dimostrano nocivi nella riabilitazione di un paziente così complesso. Obiettivo: l’obiettivo di questa Scoping Review è quello di indagare la presenza di eventi avversi riportati in letteratura che possono insorgere nella riabilitazione volta al recupero del cammino nel paziente post stroke. Inoltre, si cerca di individuare quali strategie terapeutiche non siano applicabili e sicure nell’ambito della neuroriabilitazione. Metodi: la ricerca è avvenuta consultando più banche dati online come Pubmed, Cochrane Library, PEDro, il motore di ricerca Google Scholar; il tutto tramite ricerca manuale bibliografica. Sono stati poi analizzati gli articoli pertinenti rispetto al nostro quesito di partenza, prendendo in considerazione qualsiasi tipologia di studio e senza porre limiti di lingua. Risultati: sono stati individuati 53 articoli secondo i criteri di eleggibilità, di cui: 28 RCT, 8 Systematic Reviews, 7 studi pilota, 4 meta – analisi, 2 studi cross-sectional, 2 studi osservazionali prospettici, 1 studio preliminare e 1 studio post hoc di 2 RCT. Il processo di selezione degli articoli è stato riportato utilizzando un diagramma di flusso, mentre il loro contenuto è sintetizzato in tabella sinottica. Conclusione: L’analisi degli studi segue l’applicazione della stringa di ricerca. Dall’analisi attuale della letteratura non viene evidenziata l’insorgenza di eventi avversi gravi e trattamento-correlati, che fossero responsabili di un cambiamento nella pratica clinica. Sono stati rilevati invece, alcuni eventi avversi di grado lieve o moderato, non sempre direttamente correlabili al trattamento proposto.

Genomics of pyrrolnitrin biosynthetic loci: evidence for conservation and whole-operon mobility within Gram-negative bacteria

Pyrrolnitrin (PRN) is a tryptophan-derived secondary metabolite produced by a narrow range of Gram-negative bacteria. The PRN biosynthesis by rhizobacteria presumably has a key role in their life strategies and in the biocontrol of plant diseases. The biosynthetic operon that encodes the pathway that converts tryptophan to PRN is composed of four genes, prnA through D, whose diversity, genomic context and spread over bacterial genomes are poorly understood. Therefore, we launched an endeavour aimed at retrieving, by in vitro and in silico means, diverse bacteria carrying the prnABCD biosynthetic loci in their genomes. Analysis of polymorphisms of the prnD gene sequences revealed a high level of conservation between Burkholderia, Pseudomonas and Serratia spp. derived sequences. Whole-operon- and prnD-based phylogeny resulted in tree topologies that are incongruent with the taxonomic status of the evaluated strains as predicted by 16S rRNA gene phylogeny. The genomic composition of c. 20 kb DNA fragments containg the PRN operon varied in different strains. Highly conserved and distinct transposase-encoding genes surrounding the PRN biosynthetic operons of Burkholderia pseudomallei strains were found. A prnABCD-deprived genomic region in B. pseudomallei strain K96243 contained the same gene composition as, and shared high homology with, the flanking regions of the PRN operon in B. pseudomallei strains 668, 1106a and 1710b. Our results strongly suggest that the PRN biosynthetic operon is mobile. The extent, frequency and promiscuity of this mobility remain to be understood.