A functional screen identifies lateral transfer of beta-glucuronidase (gus) from bacteria to fungi

Lateral gene transfer (LGT) from prokaryotes to microbial eukaryotes is usually detected by chance through genome-sequencing projects. Here, we explore a different, hypothesis-driven approach. We show that the fitness advantage associated with the transferred gene, typically invoked only in retrospect, can be used to design a functional screen capable of identifying postulated LGT cases. We hypothesized that beta-glucuronidase (gus) genes may be prone to LGT from bacteria to fungi (thought to lack gus) because this would enable fungi to utilize glucuronides in vertebrate urine as a carbon source. Using an enrichment procedure based on a glucose-releasing glucuronide analog (cellobiouronic acid), we isolated two gus(+) ascomycete fungi from soils (Penicillium canescens and Scopulariopsis sp.). A phylogenetic analysis suggested that their gus genes, as well as the gus genes identified in genomic sequences of the ascomycetes Aspergillus nidulans and Gibberella zeae, had been introgressed laterally from high-GC gram(+) bacteria. Two such bacteria (Arthrobacter spp.), isolated together with the gus(+) fungi, appeared to be the descendants of a bacterial donor organism from which gus had been transferred to fungi. This scenario was independently supported by similar substrate affinities of the encoded beta-glucuronidases, the absence of introns from fungal gus genes, and the similarity between the signal peptide-encoding 5' extensions of some fungal gus genes and the Arthrobacter sequences upstream of gus. Differences in the sequences of the fungal 5' extensions suggested at least two separate introgression events after the divergence of the two main Euascomycete classes. We suggest that deposition of glucuronides on soils as a result of the colonization of land by vertebrates may have favored LGT of gus from bacteria to fungi in soils.

Organizations as intergroup contexts: Communication, discourse, and identification

wenty-eight international scholars contribute 11 chapters on the key role of communication in intergroup relations. Following an introductory essay on intergroup theory and communication processes, the text focuses on specific intergroup contexts, examining communication within and between cultural, disability, age, sex and sexuality, and language groups. The remaining chapters explore the communicating of identity across communication contexts, including small group, organizational, mass, and Internet communications. The text is designed for scholars in the fields of communication and intergroup social psychology, and is also suited for use in upper- division undergraduate and introductory graduate courses in those areas. Annotation ©2004 Book News, Inc., Portland, OR

Who's at risk: Answerability and the critical possibilities of classroom discourse

Our aim in this article is twofold. First, we challenge the essentialized notion of adolescents and young people as perpetually driven to resist the authority of adults. At the same time, we disrupt linguistic conceptions of adolescent discourse, along with the discourse of youth at risk, by analyzing a transcript of classroom discourse that reflects an exchange between a highly regarded and well liked preservice teacher and his students. This representative transcript highlights the preservice teacher's ability to query, without a concomitant ability to listen, respond, and build a classroom dialogue with his students; what we call here a Socratic monologue. Second, we link the notions of dialogue and responsiveness to Bakhtin's concept of answerability, emphasizing the joint construction of classroom discourse as an ethically answerable relation between teacher and students.

The theatre programme : a public discourse at a staging of Maxwell Anderson's "Anne of the Thousand Days"

The term ’public discourses’ describes a range of texts or signifiers that inform the conditions of audience reception. Public discourses include myriad written, visual, spatial, auditory and sensory texts experienced by an audience at a particular theatrical event. Ric Knowles first introduced this term in his recent work Reading the Material Theatre. Whereas Knowles was interested in how public discourses modified the conditions of reception, my broader research is to explore how these public discourses become texts in themselves. This paper will discuss one public discourse, the theatre programme, as it related to a staging of Maxwell Anderson’s Anne of the Thousand Days at the Brisbane Powerhouse in June 2006. The significance of the programme was explored at symposiums held after the performances. Audiences generally view programmes before a performance and after a performance and its significance as a written text changes. The program became a sign vehicle that worked to expound and explicate the meaning of the play for the audience. This public discourse became a significant written text contributing to the textual whole of the theatrical event.

An alginate-based hybrid system for growth factor delivery in the functional repair of large bone defects

The treatment of challenging fractures and large osseous defects presents a formidable problem for orthopaedic surgeons. Tissue engineering/regenerative medicine approaches seek to solve this problem by delivering osteogenic signals within scaffolding biomaterials. In this study, we introduce a hybrid growth factor delivery system that consists of an electrospun nanofiber mesh tube for guiding bone regeneration combined with peptide-modified alginate hydrogel injected inside the tube for sustained growth factor release. We tested the ability of this system to deliver recombinant bone morphogenetic protein-2 (rhBMP-2) for the repair of critically-sized segmental bone defects in a rat model. Longitudinal [mu]-CT analysis and torsional testing provided quantitative assessment of bone regeneration. Our results indicate that the hybrid delivery system resulted in consistent bony bridging of the challenging bone defects. However, in the absence of rhBMP-2, the use of nanofiber mesh tube and alginate did not result in substantial bone formation. Perforations in the nanofiber mesh accelerated the rhBMP-2 mediated bone repair, and resulted in functional restoration of the regenerated bone. [mu]-CT based angiography indicated that perforations did not significantly affect the revascularization of defects, suggesting that some other interaction with the tissue surrounding the defect such as improved infiltration of osteoprogenitor cells contributed to the observed differences in repair. Overall, our results indicate that the hybrid alginate/nanofiber mesh system is a promising growth factor delivery strategy for the repair of challenging bone injuries.

Exploring retinal and functional markers of diabetic neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most debilitating complications of diabetes. DPN is a major cause of foot ulceration and lower limb amputation. Early diagnosis and management is a key factor in reducing morbidity and mortality. Current techniques for clinical assessment of DPN are relatively insensitive for detecting early disease or involve invasive procedures such as skin biopsies. There is a need for less painful, non-invasive and safe evaluation methods. Eye care professionals already play an important role in the management of diabetic retinopathy; however recent studies have indicated that the eye may also be an important site for the diagnosis and monitoring of neuropathy. Corneal nerve morphology has been shown to be a promising marker of diabetic neuropathy occurring elsewhere in the body, and emerging evidence tentatively suggests that retinal anatomical markers and a range of functional visual indicators could similarly provide useful information regarding neural damage in diabetes – although this line of research is, as yet, less well established. This review outlines the growing body of evidence supporting a potential diagnostic role for retinal structure and visual functional markers in the diagnosis and monitoring of peripheral neuropathy in diabetes.