bluuebunny/crossref_metadata_2025 huggingface dataset:
Problem‐solving experiences among elders living alone in eastern Taiwan
Authors: Tsai Hsiu‐Hsin , Tsai Yun‐Fang
Published: May 2007

Aim.  To explore problem‐solving experiences among older people living alone in eastern Taiwan.

Background.  Elders living alone in Taiwan have a low participation rate in government social support programmes. Providing sufficient care for this population of elders requires knowing not only their problems, but also how and when they seek help solve their problems.

Design.  Qualitative research was used to gain a deeper understanding of the problem‐solving experiences of older people living alone.

Methods.  Elders living alone (n = 9) were recruited from a remote area of Taiwan. Data were gathered in audiotaped, semi‐structured interviews and analysed by content analysis.

Results.  Participants used both internal and external resources to solve problems through an appraisal process. Their internal resources included self‐perception of health status, preventive coping strategies, flexible coping ability and being resigned to one's situation. Their external resources included both human and environmental resources. Based on their lived experience, participants appraised the usefulness of both internal and external resources before deciding whether to seek help from external resources.

Conclusion.  In Chinese society, maintaining a balance between internal and external resources is an important mechanism for elders in solving problems.

Relevance to clinical practice.  Our findings may enhance policy makers’ and healthcare providers’ understanding of the problem‐solving experiences of elders who live alone in Taiwan. In practical terms, these findings can be used to improve the elderly people's use of support systems in their community.
Patients experiencing local anaesthesia and hip surgery
Authors: Mauleon Annika L , Palo‐Bengtsson Liisa , Ekman Sirkka‐Liisa
Published: May 2007

Aims and objectives.  The aim of this study was to show what the experience of local anaesthesia and a surgical situation meant to patients.

Background.  Many patients who receive local anaesthesia will remain awake during surgery. The very fact of staying awake causes psychological and psychosocial needs. These needs must be met and it is therefore important to identify them.

Design/method.  Seven patients (aged 61–79) experiencing local anaesthesia and hip surgery (hip replacement surgery or repair of fractured hip) were interviewed. An interpretive phenomenological method developed by Benner was used to extract the experience of what it means to be in local anaesthesia and surgery. One paradigm case is used to illustrate the results.

Results.  Results show that the well‐being and comfort of patients is compromised by challenges such as severe pain and long waits, which may be experienced as endless and which leave the patient thinking of nothing else. By contrast, the experience of trust helps the patient to feel control even in situations where the treatment is hard to grasp.

Conclusions.  The results highlight that local anaesthesia and surgery force patients to overcome and handle experiences of pain, trust and distrust as well as feelings of alienation and unreality.

Relevance to clinical practice.  The results illustrate the patient's needs, as seen from the patient's perspective. A shared experience makes it possible to understand, and thus to recognize, the required qualitative care to facilitate and to help the patient to remain in control and face the psychological challenges presented by anaesthesia care and surgical situations.
Using action research to construct national evidence‐based nursing care guidance for gerontological nursing
Authors: Booth Jo , Tolson Debbie , Hotchkiss Rhona , Schofield Irene
Published: May 2007

Aim.  This paper explores the development of a low‐cost, involving methodology for constructing nursing‐focused evidence‐based national care guidance, known as Best Practice Statements, the intended users of which are gerontological nurses practising throughout Scotland.

Design.  The Best Practice Statement construction methodology forms one cycle in a five‐year longitudinal action research study that aims to achieve evidence‐based nursing, facilitate professional networking to support practice development and promote the principles and practice of gerontological nursing. Achieving these aims involved designing a virtual Practice Development College.

Methods.  A Community of Practice comprising practising gerontological nurses, expert advisors, academic teaching and research nurses collaborated in face‐to‐face meetings and in the virtual Practice Development College to delineate and refine the procedural model for Best Practice Statement construction. Focus groups, telephone interviews, analysis of on‐line archives and documentary outputs formed the analytic dataset.

Results.  Qualitative analysis indicated that, from the perspective of the community of practice, the emerging methodology facilitated the melding of knowledge sources reflecting the dominant evidence hierarchy with other forms of evidence valued by gerontological nurses, in the Best Practice Statement.

Relevance to clinical practice.  Current methods of care guidance construction rarely address the concerns of nurses and the evidence from which guidelines are developed is narrowly defined with regard to inclusion and acceptability. In contrast this model focuses on nursing issues, embraces a wider definition of evidence and ensures that the published Best Practice Statements are credible and achievable in gerontological practice, where they are tested and refined as an inherent aspect of the development process.
Specificity and resilience in the arbuscular mycorrhizal fungi of a natural woodland community
Authors: HELGASON THORUNN , MERRYWEATHER JAMES W. , YOUNG J. PETER W. , FITTER ALASTAIR H.
Published: May 2007

The composition of communities of arbuscular mycorrhizal (AM) fungi can have a large effect on the performance of their plant hosts. The role of individual fungal species in shaping this response is as yet unresolved.

We have used the fungicide benomyl to alter the community of AM fungi in undisturbed monoliths of soil in a natural community. Changes in the community were characterized by root colonization (%RLC), cloning, sequencing and tRFLP of a partial SSUrDNA fragment. Eleven plant species were sufficiently abundant in the monoliths to be examined.

In the highly mycorrhiza‐dependent perennial herb Ajuga reptans, phosphate concentration was significantly reduced after benomyl treatment over a full growing season. The other plant species showed low colonization and no significant difference in phosphate concentration after benomyl treatment.

Although colonization in A. reptans was reduced, many mycorrhizal fungi survived in the roots. Some became more abundant following fungicide treatment, suggesting competitive release. Fungi that increased were generalists that have been identified in field samples from published studies colonizing a wide range of plant species. Those that declined were specialists with a narrow host range; five types had not been recorded previously in field samples.

AM fungi in this study differed greatly in their response to perturbation, independent of the identity of the host plant. If such functional diversity is widespread, then elucidating the part played by AM fungal diversity in regulating plant community structure will be key to our understanding and management of ecosystems.
Differences in resprouting ability are not related to seed size or seedling growth in four riparian woody species
Authors: CHONG CAROLINE , EDWARDS WILL , WAYCOTT MICHELLE
Published: May 2007

Resprouting is a key plant attribute facilitating persistence in disturbance‐prone environments. Resprouting ability in seedlings may depend on both developmental ontogeny and seed size. However, the relationships between these factors are not well explored, especially for woody species with comparatively small seeds and epigeal germination.

We investigated resprouting capacity in seedlings from four subtropical, riparian, Myrtaceous tree species, Melaleuca leucadendra, Asteromyrtus symphyocarpa, Eucalyptus camaldulensis var. obtusa and Tristaniopsis laurina, displaying these characteristics. We recorded resprouting in response to simulated disturbance as a function of seed mass and developmental age (5–150 days post‐emergence) and examined the acquisition of resprouting ability in relation to growth and biomass allocation patterns.

Patterns of resprouting were distinct among species, but the acquisition of resprouting ability was not determined by seed mass. The ‘small’ seeded M. leucadendra and the ‘intermediate’ seeded E. camaldulensis showed unexpectedly high shoot resprouting vigour from cotyledon stage (70% resprouting at 5 days post‐emergence), as well as greatest ongoing allocation to root mass and lateral root development. In contrast, in A. symphyocarpa (another species with ‘intermediate’ seed mass) and T. laurina (a ‘large’ seeded species) resprouting rates during early development were much lower (< 10%), although there was a trend towards increasing resprouting ability with age in A. symphyocarpa (> 150 days). Resprouting capacity was also independent of seedling size and relative growth rate.

Our results indicate that the size‐dependency of resprouting capacity varies considerably among these species. This suggests physiological and morphological species traits other than those directly related to reserve size or relative growth rate may convey survivorship in river environments.

Our findings show that resprouting capacity was not related to seed size and seedling growth patterns in these four species. This is different to evidence from comparative studies undertaken in fire‐prone and other temperate environments. A broader survey of seedling resprouting ability including more species is required to determine the generality of our findings in riparian species.
Disturbance is the principal α‐scale filter determining niche differentiation, coexistence and biodiversity in an alpine community
Authors: PIERCE SIMON , LUZZARO ALESSANDRA , CACCIANIGA MARCO , CERIANI ROBERTA M. , CERABOLINI BRUNO
Published: May 2007

Many current biodiversity theories assume that resource competition determines niche segregation and thus coexistence within communities (i.e. at the α‐scale). However, the action of disturbance, creating heterogeneous environments and suppressing potential dominants, may also be important for biodiversity maintenance.

Hypothesis: subordinate species exhibit primarily opportunistic (ruderal) survival strategies, with increasing disturbance intensity constraining dominant species – favouring opportunistic strategies and thus functional and species diversity.

The diversity, character and frequency of strategies in an alpine sedge‐dominated vascular plant community were quantified in situ using CSR (competitor, stress‐tolerator, ruderal) classification, and compared with a pasture in the same alpine vegetation belt (i.e. with additional disturbance). Adaptive trends were confirmed by independent multivariate analysis [detrended correspondence analysis (DCA) and non‐metric multidimensional scaling (NMDS)].

The extremely stress‐tolerant sedge Carex curvula (C : S : R = 17.2 : 72.9 : 9.9%) dominated the relatively undisturbed community (frequency = 52%), with 32 subordinates (typically < 5%) exhibiting a functional spectrum encompassing stress tolerance to ruderalism, but not competitive strategies. With grazing, the community exhibited weaker co‐dominance by five species, greater biodiversity (76 species) and greater functional diversity, characterized by larger numbers of ruderals and some competitive‐ruderals. The principal variation in both DCA1 and NMDS1 for both communities directly reflected CSR strategy spectra, confirmed by Spearman's correlation.

Dominance by stress‐tolerators and restricted functional diversity demonstrates habitat‐level (β‐scale) functional convergence in response to stress. A spectrum of S to R strategies demonstrates α‐scale functional divergence in response to differential stress and disturbance. Grazing suppresses potentially dominant species and favours diversity, with the additional presence of competitive‐ruderals suggestive of a more intricate niche topology including more relaxed abiotic opportunities.

Natural communities are not necessarily structured according to the rules of resource competition models, as these fail to account for disturbance and facilitation processes.
The carbon costs for host trees of a phloem‐feeding herbivore
Authors: DUNGAN ROGER J. , TURNBULL MATTHEW H. , KELLY DAVE
Published: May 2007

Through its effect on plant productivity and fitness, herbivory can regulate forest diversity and ecosystem productivity. We used the interaction between phloem‐feeding scale insects [Ultracoelostoma assimile(Homoptera: Coelostomidiidae)] and the beech trees [Nothofagus solandrivar.solandri(Hook f.) Oerst.] they feed on to estimate directly the carbon costs of herbivory for a forest tree species over two consecutive years. The scale insects live on the bark of tree trunks and branches, and excrete readily collected droplets of carbon‐rich honeydew – this allows us to make an estimate of the carbon cost of herbivory that is not complicated by feeding damage to leaves and buds.

Canopy photosynthesis (A) was estimated with an environmentally driven process‐based model, developed with parameters derived from measurements of photosynthesis on trees with (HD+) and without (HD–) honeydew scale insects during year 1. Honeydew dry matter production (PHD) was estimated from values for air temperature and humidity, and accounting for variation in honeydew production due to host‐tree diameter. The carbon cost of scale insect herbivory,CHD, was estimated asPHD/AHD+× 100%, whereAHD+is canopy photosynthesis for trees with scale insects.

Over the two years annual canopy photosynthesis at the site was 1720 g C m−2ground area. In spring–summer, values for parameters describing photosynthesis (Vcmax, the maximum rate of rubisco‐catalysed RuBP carboxylation, andJmax, the rate of electron transport when irradiance is saturating) were 44% and 66% higher, respectively, in infested, as opposed to uninfested, trees. Consequently, for equivalent basal area, annual canopy photosynthesis was 4% greater for infested trees.

Assuming that honeydew dry matter was 42% carbon by mass, annual honeydew production was 59 g C m−2ground area, which represents 4% of infested‐tree gross photosynthesis (c. 8% of net photosynthesis). Daily values of honeydew production were highest on cloudy days in summer, when warm humid conditions resulted in high values forPHDbut cloud cover reducedAHD+; on these daysCHDcould be > 50% ofAHD+. Values forPHDare remarkably similar to the differences betweenAHD+andAHD–, suggesting that HD+ trees may be able to compensate fully for the loss of carbon to herbivory. Our modelling results thus suggest that while the honeydew insects harvest relatively large amounts of carbohydrate from their host trees, the consequences of this for tree growth and reproduction may be small.
The role of soil resources in an exotic tree invasion in Texas coastal prairie
Authors: SIEMANN EVAN. , ROGERS WILLIAM E.
Published: May 2007

Variation in resource requirements among plant species may cause changes in community composition when resource supply rates vary. Because exotic plants may differ in their requirements compared with native plants, changes in resource levels or ratios may change their invasive potential. The concentration hypothesis, nutrient balance hypothesis and resource ratio hypothesis make different predictions regarding the effects of nutrient additions on plant communities and the success of invaders.

We investigated these hypotheses using Chinese tallow tree (Sapium sebiferum), which is an aggressive invader of grasslands in the southern USA. Soil nitrogen, phosphorus and potassium were manipulated in a full factorial field experiment in a Texas coastal prairie.

Survival of Sapium seedlings over three growing seasons was independent of all three types of nutrient additions, alone or in any combination. Adding nitrogen or potassium increased the mass and height of Sapium seedlings. Adding phosphorus increased the mass and height of Sapium seedlings only when nitrogen was also added. These results support the nutrient balance hypothesis, which assumes that higher tissue concentrations of a nutrient reflect a greater ability of a plant species to take up and/or conserve that nutrient.

The above‐ground biomass of background prairie vegetation was independent of the addition of each type of nutrient alone or in any combination. However, the functional composition of the community shifted from graminoids to forbs with the addition of nitrogen and from graminoids to woody plants with the addition of phosphorus. These results support the concentration hypothesis, which assumes that higher tissue concentrations of a nutrient reflect a greater requirement for that nutrient. The contrasting responses of native woody vegetation and Sapium to phosphorus addition suggest that Sapium may have unusually low demands for phosphorus relative to nitrogen for a woody plant in this community.

These results show that potassium or nitrogen addition, perhaps in combination with phosphorus addition, has the potential to accelerate the invasion of Sapium into Texas coastal prairies. Because anthropogenic nutrient additions are common in grasslands worldwide, this may help to explain the frequent success of woody species invading grasslands.
Parenting by persons with intellectual disability: an explorative study in the Netherlands
Authors: Willems D. L. , De Vries J.‐N. , Isarin J. , Reinders J. S.
Published: May 2007

Background  As a sequel to a report by the Health Council of the Netherlands on contraception in persons with intellectual disabilities (IDs), a fierce debate about parenthood by such persons occurred, in which a lack of knowledge about parenting competences became clear. Therefore, the Ministry of Health commissioned a study investigating examples of ‘successful parenthood’ by persons with IDs.

Methods  In conformity with the literature and with legal categories, we defined ‘successful parenthood’ as ‘good enough parenthood’, meaning no indications for child abuse and/or neglect, no dealings with child protection agencies and no legal custody. We combined a nationwide quantitative questionnaire study with a qualitative interview study. Questionnaires were sent to all institutions involved in caring for persons with ID, interviews were held with ‘good enough’ parents and their professional caregivers, selected on the basis of returned questionnaires.

Results  Parenthood occurs in around 1.5% of persons with ID in the Netherlands and is mostly restricted to those with mild handicaps. In total, 51% of the cases were regarded, by caregivers, as not‐good‐enough parenthood, 33% were clearly good enough and 16% were doubtful. Predicting factors included the ability and the willingness to follow advice, the quality of the social network and the acceptance of parenting in the community. However, there is not one decisive predicting factor; particularly, the predictive value of the IQ alone is small.

Conclusions  A general policy of discouragement of parenthood, as advocated by the Dutch Ministry, is not supported by our results; moreover, it would probably be impossible and have negative effects on social acceptance of parents with ID. The overall conclusion from the study therefore is that some kind of balancing model, in which positive and negative factors are weighed, may be useful to predict success and need for support.
Symbols can improve the reading comprehension of adults with learning disabilities
Authors: Jones F. W. , Long K. , Finlay W. M. L.
Published: May 2007

Background  This study aimed to test the hypothesis that adding symbols to written text can improve its comprehensibility for adults with learning disabilities.

Methods  Nineteen adults with mild or borderline learning disabilities attempted to read four short passages of text, two of which had Widgit Rebus symbols added to them. Following each passage, they were asked questions to test their comprehension. A counterbalanced design was employed.

Results  Participants’ comprehension scores were significantly higher for the symbolized passages than the non‐symbolized ones.

Conclusions  Adding symbols to written text can make comprehension easier for some adults with mild and borderline learning disabilities. Future research, exploring how to do this most effectively, would be worthwhile.
Understanding of facial expressions of emotion by children with intellectual disabilities of differing aetiology
Authors: Wishart J. G. , Cebula K. R. , Willis D. S. , Pitcairn T. K.
Published: May 2007

Background  Interpreting emotional expressions is a socio‐cognitive skill central to interpersonal interaction. Poor emotion recognition has been reported in autism but is less well understood in other kinds of intellectual disabilities (ID), with procedural differences making comparisons across studies and syndromes difficult. This study aimed to compare directly facial emotion recognition skills in children with fragile X syndrome (FXS), Down's syndrome (DS) and non‐specific intellectual disability (NSID), contrasting ability and error profiles with those of typically developing (TD) children of equivalent cognitive and linguistic status.

Methods  Sixty children participated in the study: 15 FXS, 15 DS, 15 NSID and 15 TD children. Standardised measures of cognitive, language and socialisation skills were collected for all children, along with measures of performance on two photo‐matching tasks: an ‘identity‐matching’ task (to control for basic face‐processing ability) and an ‘emotion‐matching’ task (happiness, sadness, anger, surprise, fear or disgust).

Results  Identity‐matching ability did not differ across the four child groups. Only the DS group performed significantly more poorly on the emotion‐matching task and only in comparison to the TD group, with fear recognition an area of particular difficulty.

Conclusion  Findings support previous evidence of emotion recognition abilities commensurate with overall developmental level in children with FXS or NSID, but not DS. They also suggest, however, that syndrome‐specific difficulties may be subtle and detectable, at least in smaller‐scale studies, only in comparison with TD matches, and not always across syndromes. Implications for behavioural phenotype theory, educational interventions and future research are discussed.
Influences of body posture on duration of oral swallowing in normal young adults
Authors: INAGAKI D. , MIYAOKA Y. , ASHIDA I. , UEDA K. , YAMADA Y.
Published: May 2007

Summary  The primary purpose of this study was to determine whether body posture altered the duration of oral swallowing. To answer this question, we recorded electromyograms (EMGs) from the anterior tongue and suprahyoid (SH) muscles as well as laryngeal movement associated with swallowing in nine normal young subjects. The subjects swallowed a test food after receiving a signal while in four randomly set postures: upright, two inclined (60° and 30° to the horizontal), and supine positions. We measured the durations from the start to the peak and from the peak to the end of the integrated tongue and SH EMGs. We assumed that the duration from the start to the peak of the integrated SH EMG would correspond to the duration of oral swallowing. The average duration from the start to the peak of the integrated SH EMG decreased after moving from the upright to the inclined and supine positions. The decrease in the duration was statistically significant and consistent for three experimental sessions. The duration from the start to the peak of the integrated tongue EMG during swallowing tended to decrease after lying down, but not significantly. The postural changes did not affect the remaining four durations. The decrease in the duration of oral swallowing induced by lying down suggests that the gravitational force placed on the test food facilitates the swallowing reflex. Large variation in the tongue activity during swallowing among the subjects can probably be attributed to the lack of a significant decrease in the duration of the tongue activity.
Using fluorescently labelled M13‐tailed primers to isolate 45 novel microsatellite loci from the arboviral vector Culex tarsalis
Authors: VENKATESAN M. , HAUER M. C. , RASGON J. L.
Published: May 2007

Abstract Culex tarsalis Coquillett (Diptera: Culicidae) is a highly efficient arbovirus vector. Spatial and temporal heterogeneity have been observed in Cx tarsalis for phenotypic traits including autogeny, virus susceptibility and host preference. Genetic differences between populations may in part explain these observations. Using the M13‐tailed primer method, we identified 45 novel polymorphic microsatellite markers from microsatellite‐enriched Cx tarsalis genomic libraries. The M13‐tailed primer method was more efficient in identifying useful loci than traditional screening by acrylamide gel electrophoresis. These markers will be useful for investigating genetic questions in this important vector mosquito.
Deltamethrin‐impregnated bednets reduce human landing rates of sandfly vector Lutzomyia longipalpis in Amazon households
Authors: COURTENAY O. , GILLINGWATER K. , GOMES P. A. F. , GARCEZ L. M. , DAVIES C. R.
Published: May 2007

Abstract The entomological efficacy of using 25% deltamethrin EC insecticide‐treated bednets (ITNs) was evaluated against the sandfly Lutzomyia longipalpis Lutz and Neiva (Diptera: Psychodidae), the principal vector of zoonotic visceral leishmaniasis (ZVL) in Latin America. A crossover field study in Amazon Brazil (Marajó Island, Pará State) demonstrated that, compared with untreated nets, the insecticide increased the barrier effect of nets by 39% (95% confidence interval [CI] 34–44%), reduced human landing rates by 80% (95% CI 62–90%) and increased the 24‐h mortality rate from 0% to 98% (95% CI 93–99%) inside ITNs. The presence of an ITN also reduced the human landing rate on unprotected persons outside the net in the same room by 56% (95% CI 52–59%), and increased 24‐h mortality to 68% (95% CI 62–73%) compared to 0.4% (0.1−2.0%) in untreated houses. The reduction in human landing rates in ITN rooms was associated with a doubling in the proportion of sandflies alighting on walls compared with that in untreated rooms, which was attributed to insecticide‐induced excito‐repellency. There was no evidence that sandflies were diverted onto unprotected hosts. Human landing catches inside houses peaked between 19.00 hours and 23.00 hours and declined steadily to zero at 02.00 hours and thereafter. House‐to‐house questionnaires established that only 34% of households owned at least one net (median two, range 1–8), only 20% of the population slept under a net (33% of 0–5‐year‐old children), and the majority (73%) of the population slept in hammocks. Combined data pertaining to sleeping times for children and sandfly activity period indicate that > 50% of sandfly bites inside houses, and substantially more outside houses, were taken before a third of children were potentially protected by a net. This study demonstrates the clear entomological efficacy of ITNs against Lu. longipalpis in this endemic region. The effectiveness of ITNs at preventing ZVL infection and disease has still to be evaluated.
TUP1 disruption in Cryptococcus neoformans uncovers a peptide‐mediated density‐dependent growth phenomenon that mimics quorum sensing
Authors: Lee Hyeseung , Chang Yun C. , Nardone Glenn , Kwon‐Chung Kyung J.
Published: May 2007

Cryptococcus neoformans is a pathogenic yeast that causes life‐threatening meningoencephalitis and grows well on mycological media regardless of inoculum size. Interestingly, a deletion of the global repressor TUP1 in C. neoformans uncovered a density‐dependent growth phenotype reminiscent of the quorum‐sensing phenomenon. An inoculum size of lower than 103 cells of the tup1Δ strain failed to form colonies on agar media while inocula of 105−106 cells per plate formed a lawn. This phenotype, expressed as the inability to grow at low cell densities, was rescued by the culture filtrate from a high cell density tup1Δ culture and the active molecule in this culture filtrate was identified to be an oligopeptide composed of 11 amino acids. Activity assays, using a synthetic version of the peptide with strains harbouring a deletion of the corresponding gene, proved that the oligopeptide functioned as an autoregulatory molecule responsible for the density‐dependent phenotype. Although a density‐dependent growth phenotype has been reported in several species of Ascomycetes, no peptide has been reported to function as an autoregulator in the Kingdom Fungi. The identification of an 11‐mer peptide as an autoregulatory molecule in C. neoformans suggests that a diverse mechanism of cell‐to‐cell communication exists in the Kingdom Fungi.
SapB and the chaplins: connections between morphogenetic proteins in Streptomyces coelicolor
Authors: Capstick David S. , Willey Joanne M. , Buttner Mark J. , Elliot Marie A.
Published: May 2007

Morphogenesis in the streptomycetes features the differentiation of substrate‐associated vegetative hyphae into upwardly growing aerial filaments. This transition requires the activity of bld genes and the secretion of biosurfactants that reduce the surface tension at the colony–air interface enabling the emergence of nascent aerial hyphae. Streptomyces coelicolor produces two classes of surface‐active molecules, SapB and the chaplins. While both molecules are important for aerial development, nothing is known about the functional redundancy or interaction of these surfactants apart from the observation that aerial hyphae formation can proceed via one of two pathways: a SapB‐dependent pathway when cells are grown on rich medium and a SapB‐independent pathway on poorly utilized carbon sources such as mannitol. We used mutant analysis to show that while the chaplins are important, but not required, for development on rich medium, they are essential for differentiation on MS (soy flour mannitol) medium, and the corresponding developmental defects could be suppressed by the presence of SapB. Furthermore, the chaplins are produced by conditional bld mutants during aerial hyphae formation when grown on the permissive medium, MS, suggesting that the previously uncharacterized SapB‐independent pathway is chaplin dependent. In contrast, a bld mutant blocked in aerial morphogenesis on all media makes neither SapB nor chaplins. Finally, we show that a constructed null mutant that lacks all chaplin and SapB biosynthetic genes fails to differentiate in any growth condition. We propose that the biosurfactant activities of both SapB and the chaplins are essential for normal aerial hyphae formation on rich medium, while chaplin biosynthesis and secretion alone drives aerial morphogenesis on MS medium.
Sre1p, a regulator of oxygen sensing and sterol homeostasis, is required for virulence in Cryptococcus neoformans
Authors: Chang Yun C. , Bien Clara M. , Lee Hyeseung , Espenshade Peter J. , Kwon‐Chung Kyung J.
Published: May 2007

Cryptococcus neoformans is an environmental pathogen requiring atmospheric levels of oxygen for optimal growth. Upon inhalation, C. neoformans disseminates to the brain and causes meningoencephalitis, but the mechanisms by which the pathogen adapts to the low‐oxygen environment in the brain have not been investigated. We found that SRE1, a homologue of the mammalian sterol regulatory element‐binding protein (SREBP), functions in an oxygen‐sensing pathway. Low oxygen decreased sterol synthesis in C. neoformans and triggered activation of membrane‐bound Sre1p by the cleavage‐activating protein, Scp1p. Microarray and Northern blot analysis demonstrated that under low oxygen, Sre1p activates genes required for ergosterol biosynthesis and iron uptake. Consistent with these regulatory functions, sre1Δ cells were hypersensitive to azole drugs and failed to grow under iron‐limiting conditions. Importantly, sre1Δ cells failed to produce fulminating brain infection in mice. Our in vitro data support a model in which Sre1p is activated under low oxygen leading to the upregulation of genes required for sterol biosynthesis and growth in a nutrient‐limiting environment. Animal studies confirm the importance of SRE1 for C. neoformans to adapt to the host environment and to cause fatal meningoencephalitis, thereby identifying the SREBP pathway as a therapeutic target for cryptococcosis.
A novel compartment, the ‘subapical stem’ of the aerial hyphae, is the location of a sigN‐dependent, developmentally distinct transcription in Streptomyces coelicolor
Authors: Dalton Kate A. , Thibessard Annabelle , Hunter James I. B. , Kelemen Gabriella H.
Published: May 2007

Streptomyces coelicolor has nine SigB‐like RNA polymerase sigma factors, several of them implicated in morphological differentiation and/or responses to different stresses. One of the nine, SigN, is the focus of this article. A constructed sigN null mutant was delayed in development and exhibited a bald phenotype when grown on minimal medium containing glucose as carbon source. One of two distinct sigN promoters, sigNP1, was active only during growth on solid medium, when its activation coincided with aerial hyphae formation. Transcription from sigNP1 was readily detected in several whi mutants (interrupted in morphogenesis of aerial mycelium into spores), but was absent from all bld mutants tested, suggesting that sigNP1 activity was restricted to the aerial hyphae. It also depended on sigN, thus sigN was autoregulated. Mutational and transcription studies revealed no functional significance to the location of sigN next to sigF, encoding another SigB‐like sigma factor. We identified another potential SigN target, nepA, encoding a putative small secreted protein. Transcription of nepA originated from a single, aerial hyphae‐specific and sigN‐dependent promoter. While in vitro run‐off transcription using purified SigN on the Bacillus subtilis ctc promoter confirmed that SigN is an RNA polymerase sigma factor, SigN failed to initiate transcription from sigNP1 and from the nepA promoter in vitro. Additional in vivo data indicated that further nepA upstream sequences, which are likely to bind a potential activator, are required for successful transcription. Using a nepA–egfp transcriptional fusion we located nepA transcription to a novel compartment, the ‘subapical stem’ of the aerial hyphae. We suggest that this newly recognized compartment defines an interface between the aerial and vegetative parts of the Streptomyces colony and might also be involved in communication between these two compartments.
The Pseudomonas putida Crc global regulator is an RNA binding protein that inhibits translation of the AlkS transcriptional regulator
Authors: Moreno Renata , Ruiz‐Manzano Ana , Yuste Luis , Rojo Fernando
Published: May 2007

The Crc protein is a global regulator that controls the hierarchical assimilation of carbon sources in Pseudomonads by inhibiting expression of several catabolic pathways. Crc does not bind DNA and its mechanism of action has remained elusive. Among other genes, Crc inhibits expression of alkS, the transcriptional activator of the Pseudomonas putida OCT plasmid alkane degradation pathway. AlkS activates expression of its own gene. In the presence of saturating AlkS levels, translational fusions of alkS to the lacZ reporter gene were responsive to Crc, but transcriptional fusions were not. In translational fusions, the first 33 nt of alkS mRNA, which includes up to position +3 relative to the translation start site, were sufficient to confer an efficient response to Crc. In vitro, purified Crc could bind specifically to an alkS mRNA fragment spanning positions +1 to +43, comprising the translation initiation region. We have previously shown that Crc has little effect on the stability of alkS mRNA. We conclude that Crc modulates AlkS levels by binding to the translation initiation region of alkS mRNA, thereby inhibiting translation. Because AlkS is an unstable protein present in limiting amounts, reducing its levels leads to decreased expression of all genes in the pathway.
The rotational dynamics of kinetoplast DNA replication
Authors: Liu Yanan , Englund Paul T.
Published: May 2007

Kinetoplast DNA (kDNA), from trypanosomatid mitochondria, is a network containing several thousand catenated minicircles that is condensed into a disk‐shaped structure in vivo. kDNA synthesis involves release of individual minicircles from the network, replication of the free minicircles and reattachment of progeny at two sites on the network periphery ∼180° apart. In Crithidia fasciculata, rotation of the kDNA disk relative to the antipodal attachment sites results in distribution of progeny minicircles in a ring around the network periphery. In contrast, Trypanosoma brucei progeny minicircles accumulate on opposite ends of the kDNA disk, a pattern that did not suggest kinetoplast motion. Thus, there seemed to be two distinct replication mechanisms. Based on fluorescence microscopy of the kDNA network undergoing replication, we now report that the T. brucei kinetoplast does move relative to the antipodal sites. Whereas the C. fasciculata kinetoplast rotates, that from T. brucei oscillates. Kinetoplast motion of either type must facilitate orderly replication of this incredibly complex structure.
Control of the respiratory metabolism of Thermus thermophilus by the nitrate respiration conjugative element NCE
Authors: Cava Felipe , Laptenko Oleg , Borukhov Sergei , Chahlafi Zahra , Blas‐Galindo Emilio , Gómez‐Puertas Paulino , Berenguer José
Published: May 2007

The strains of Thermus thermophilus that contain the nitrate respiration conjugative element (NCE) replace their aerobic respiratory chain by an anaerobic counterpart made of the Nrc‐NADH dehydrogenase and the Nar‐nitrate reductase in response to nitrate and oxygen depletion. This replacement depends on DnrS and DnrT, two homologues to sensory transcription factors encoded in a bicistronic operon by the NCE. DnrS is an oxygen‐sensitive protein required in vivo to activate transcription on its own dnr promoter and on that of the nar operon, but not required for the expression of the nrc operon. In contrast, DnrT is required for the transcription of these three operons and also for the repression of nqo, the operon that encodes the major respiratory NADH dehydrogenase expressed during aerobic growth. Thermophilic in vitro assays revealed that low DnrT concentrations allows the recruitment of the T. thermophilus RNA polymerase σA holoenzyme to the nrc promoter and its transcription, whereas higher DnrT concentrations are required to repress transcription on the nqo promoter. In conclusion, our data show a complex autoinducible mechanism by which DnrT functions as the transcriptional switch that allows the NCE to take the control of the respiratory metabolism of its host during adaptation to anaerobic growth.
An antisense RNA controls synthesis of an SOS‐induced toxin evolved from an antitoxin
Authors: Kawano Mitsuoki , Aravind L. , Storz Gisela
Published: May 2007

Only few small, regulatory RNAs encoded opposite another gene have been identified in bacteria. Here, we report the characterization of a locus where a small RNA (SymR) is encoded in cis to an SOS‐induced gene whose product shows homology to the antitoxin MazE (SymE). Synthesis of the SymE protein is tightly repressed at multiple levels by the LexA repressor, the SymR RNA and the Lon protease. SymE co‐purifies with ribosomes and overproduction of the protein leads to cell growth inhibition, decreased protein synthesis and increased RNA degradation. These properties are shared with several RNA endonuclease toxins of the toxin‐antitoxin modules, and we show that the SymE protein represents evolution of a toxin from the AbrB fold, whose representatives are typically antitoxins. We suggest that SymE promotion of RNA cleavage may be important for the recycling of RNAs damaged under SOS‐inducing conditions.
Whole‐genome analysis of the chromosome partitioning and sporulation protein Spo0J (ParB) reveals spreading and origin‐distal sites on the Bacillus subtilis chromosome
Authors: Breier Adam M. , Grossman Alan D.
Published: May 2007

We investigated the genome‐wide DNA binding of the chromosome partitioning and sporulation protein and ParB family member Spo0J in Bacillus subtilis using chromatin immunoprecipitation and DNA microarrays. We identified 10 parS loci to which Spo0J binds, two of which were unexpectedly distant (> 1 Mb) from the origin of replication. We used all 10 sites to refine the consensus sequence for parS. We found that Spo0J spreads along the DNA around each site. Binding was near maximal levels up to 1.6 kb away from parS, and significantly above background as far away as 18 kb. Deletion of soj (parA) had little or no effect on spreading. In contrast, the spo0J93 allele appeared to cause a significant decrease in spreading in vivo, without significantly affecting the DNA binding affinity in vitro. spo0J93 causes a phenotype similar to that of a spo0J null mutant and alters the region thought to be involved in interaction between Spo0J dimers. Our findings indicate that spreading is important for in vivo function of Spo0J. Gene expression in areas near parS sites was similar in wild type and a spo0J null mutant, indicating that binding and spreading of Spo0J on DNA does not normally silence transcription of nearby genes.
Telomere resolution by Borrelia burgdorferi ResT through the collaborative efforts of tethered DNA binding domains
Authors: Tourand Yvonne , Lee Linda , Chaconas George
Published: May 2007

Borrelia burgdorferi, a causative agent of Lyme disease, has a highly unusual segmented genome composed of both circular molecules and linear DNA replicons terminated by covalently closed hairpin ends or telomeres. Replication intermediates of the linear molecules are processed into hairpin telomeres via the activity of ResT, a telomere resolvase. We report here the results of limited proteolysis and mass spectroscopy to identify two main structural domains in ResT, separated by a chymotrypsin cleavage site between residues 163 and 164 of the 449 amino acid protein. The two domains have been overexpressed and purified. DNA electrophoretic mobility shift assays revealed that the C‐terminal domain (ResT164−449) displays sequence‐specific DNA binding to the box 3,4,5 region of the telomere, while the N‐terminal domain (ResT1−163) exhibits sequence‐independent DNA binding activity. Further analysis by DNase I footprinting supports a model for telomere resolution in which the hairpin binding module of the N‐terminal domain is delivered to the box 1,2 region of the telomere through its tethering to ResT164−449. Conversely, ResT1−164 may play an important regulatory role by modulating both sequence‐specific DNA binding activity and catalysis by the C‐terminal domain.
The RecJ DNase strongly suppresses genomic integration of short but not long foreign DNA fragments by homology‐facilitated illegitimate recombination during transformation of Acinetobacter baylyi
Authors: Harms Klaus , Schön Verena , Kickstein Eva , Wackernagel Wilfried
Published: May 2007

Homology‐facilitated illegitimate recombination (HFIR) promotes genomic integration of foreign DNA with a single segment homologous to the recipient genome by homologous recombination in the segment accompanied by illegitimate fusion of the heterologous sequence. During natural transformation of Acinetobacter baylyi HFIR occurs at about 0.01% of the frequency of fully homologous recombination. The role of the 5′ single‐strand‐specific exonuclease RecJ in HFIR was investigated. Deletion of recJ increased HFIR frequency about 20‐fold compared with wild type while homologous recombination was not affected. Illegitimate fusion sites were predominantly located within 360 nucleotides away from the homology whereas in wild type most fusion sites were distal (500–2500 nucleotides away). RecJ overproduction reduced the HFIR frequency to half compared with wild type, and transformants with short foreign DNA segments were diminished, leading to on average 866 foreign nucleotides integrated per event (682 in wild type, 115 in recJ). In recJ always the 3′ ends of donor DNA were integrated at the homology whereas in wild type these were 3′ or 5′. RecJ apparently suppresses HFIR by degrading 5′ non‐homologous DNA tails at the post‐synaptic stage. We propose that the RecJ activity level controls the HFIR frequency during transformation and the amount of foreign DNA integrated per event.
Systematic capsule gene disruption reveals the central role of galactose metabolism on Cryptococcus neoformans virulence
Authors: Moyrand Frédérique , Fontaine Thierry , Janbon Guilhem
Published: May 2007

The polysaccharidic capsule is the main virulence factor of Cryptococcus neoformans. It primarily comprised of two polysaccharides: glucuronoxylomannan (GXM, 88% of the capsule mass) and galactoxylomannan (GalXM, 7% of the capsule mass). We constructed a large collection of mutant strains in which genes potentially involved in capsule biosynthesis were deleted. We used a new post‐genomic approach to study the virulence of the strains. Primers specific for unique tags associated with the disruption cassette were used in a real‐time PCR virulence assay to measure the fungal burden of each strain in different organs of mice in multi‐infection experiments. With this very sensitive assay, we identified a putative UDP‐glucose epimerase (Uge1p) and a putative UDP‐galactose transporter (Ugt1p) essential for C. neoformans virulence. The uge1Δ and ugt1Δ strains are temperature sensitive and do not produce GalXM but synthesize a larger capsule. These mutant strains (GalXM negative, GXM positive) are not able to colonize the brain even at the first day of infection whereas GXM‐negative strains (GalXM positive) can still colonize the brain, although less efficiently than the wild‐type strain.
Identification of a system required for the functional surface localization of sugar binding proteins with class III signal peptides in Sulfolobus solfataricus
Authors: Zolghadr Behnam , Weber Stefan , Szabó Zalán , Driessen Arnold J. M. , Albers Sonja‐Verena
Published: May 2007

The hyperthermophilic archaeon Sulfolobus solfataricus contains an unusual large number of sugar binding proteins that are synthesized as precursors with a class III signal peptide. Such signal peptides are commonly used to direct archaeal flagellin subunits or bacterial (pseudo)pilins into extracellular macromolecular surface appendages. Likewise, S. solfataricus binding proteins have been suggested to assemble in higher ordered surface structures as well, tentatively termed the bindosome. Here we show that S. solfataricus contains a specific system that is needed for the functional surface localization of sugar binding proteins. This system, encoded by the bas (bindosome assembly system) operon, is composed of five proteins: basABC, three homologues of so‐called bacterial (pseudo)pilins; BasE, a cytoplasmic ATPase; and BasF, an integral membrane protein. Deletion of either the three (pseudo)pilin genes or the basEF genes resulted in a severe defect of the cells to grow on substrates which are transported by sugar binding proteins containing class III signal peptides, while growth on glucose and maltose was restored when the corresponding genes were reintroduced in these cells. Concomitantly, ΔbasABC and ΔbasEF cells were severely impaired in glucose uptake even though the sugar binding proteins were normally secreted across the cytoplasmic membrane. These data underline the hypothesis that the bas operon is involved in the functional localization of sugar binding proteins at the cell surface of S. solfataricus. In contrast to surface structure assembly systems of Gram‐negative bacteria, the bas operon seems to resemble an ancestral simplified form of these machineries.