University of Georgia

About: University of Georgia is a education organization based out in Athens, Georgia, United States. It is known for research contribution in the topics: Population & Gene. The organization has 41934 authors who have published 93622 publications receiving 3713212 citations. The organization is also known as: UGA & Franklin College.

Massively parallel 454 sequencing indicates hyperdiverse fungal communities in temperate Quercus macrocarpa phyllosphere

Abstract: * This study targeted the fungal communities in the phyllosphere of Quercus macrocarpa and compared the fungal species richness, diversity and community composition among trees located within and outside a small urban center using recently developed 454 sequencing and DNA tagging. * The results indicate that the fungal phyllosphere communities are extremely diverse and strongly dominated by ascomycetes, with Microsphaeropsis [two Operational Taxonomic Units (OTUs); 23.6%], Alternaria (six OTUs; 16.1%), Epicoccum (one OTU; 6.0%) and Erysiphe (two OTUs; 5.9%) as the most abundant genera. * Although the sequencing effort averaged 1000 reads per tree and detected nearly 700 distinct molecular OTUs at 95% internal transcribed spacer 1 similarity, the richness of the hyperdiverse phyllosphere communities could not be reliably estimated as nearly one-half of the molecular OTUs were singletons. * The fungal communities within and outside the urban center differed in richness and diversity, which were lower within the urban development. The two land-use types contained communities that were distinct and more than 10% of the molecular OTUs differed in their frequency.

From the "Good Kids" to the "Worst": Representations of English Language Learners across Educational Settings

Abstract: Based on year-long ethnographic case studies following U.S. immigrants in their last year of secondary school and first year in a 2-year community college, this article contrasts prevalent institutional images of what it means to be an English language learner in these two educational settings. The article draws on the notion of representation, or archetypal images of learner identity, arguing that representation offers a means of understanding how seemingly self-evident and unchanging identities emerge in a particular social context out of ever-evolving processes of identity (re)creation. The article compares representations of ESL student identity in the two educational institutions and illustrates the manifestation of these representations in class curricula and spoken and written interactions. Prevalent institutional images of ESL student identities were appropriated and recreated by students and educators in one context and resisted by students in another. Contending that representation is an inevitable part of human meaning making and identity formation, the article suggests that images of students and of their backgrounds, experiences, and needs not only inform curriculum but also have significant consequences for students' identities and attitudes toward classroom learning.

Delta-like 4 is the essential, nonredundant ligand for Notch1 during thymic T cell lineage commitment

Abstract: Thymic T cell lineage commitment is dependent on Notch1 (N1) receptor-mediated signaling. Although the physiological ligands that interact with N1 expressed on thymic precursors are currently unknown, in vitro culture systems point to Delta-like 1 (DL1) and DL4 as prime candidates. Using DL1- and DL4-lacZ reporter knock-in mice and novel monoclonal antibodies to DL1 and DL4, we show that DL4 is expressed on thymic epithelial cells (TECs), whereas DL1 is not detected. The function of DL4 was further explored in vivo by generating mice in which DL4 could be specifically inactivated in TECs or in hematopoietic progenitors. Although loss of DL4 in hematopoietic progenitors did not perturb thymus development, inactivation of DL4 in TECs led to a complete block in T cell development coupled with the ectopic appearance of immature B cells in the thymus. These immature B cells were phenotypically indistinguishable from those developing in the thymus of conditional N1 mutant mice. Collectively, our results demonstrate that DL4 is the essential and nonredundant N1 ligand responsible for T cell lineage commitment. Moreover, they strongly suggest that N1-expressing thymic progenitors interact with DL4-expressing TECs to suppress B lineage potential and to induce the first steps of intrathymic T cell development.

Complex pectin metabolism by gut bacteria reveals novel catalytic functions

Abstract: The metabolism of carbohydrate polymers drives microbial diversity in the human gut microbiota. It is unclear, however, whether bacterial consortia or single organisms are required to depolymerize highly complex glycans. Here we show that the gut bacterium Bacteroides thetaiotaomicron uses the most structurally complex glycan known: the plant pectic polysaccharide rhamnogalacturonan-II, cleaving all but 1 of its 21 distinct glycosidic linkages. The deconstruction of rhamnogalacturonan-II side chains and backbone are coordinated to overcome steric constraints, and the degradation involves previously undiscovered enzyme families and catalytic activities. The degradation system informs revision of the current structural model of rhamnogalacturonan-II and highlights how individual gut bacteria orchestrate manifold enzymes to metabolize the most challenging glycan in the human diet.

Engagement as flourishing: The contribution of positive emotions and coping to adolescents' engagement at school and with learning

Abstract: Fredrickson's (1998, 2001) broaden and build theory postulates that the experience of frequent positive emotions serves to broaden humans' thoughts and behaviors, resulting in accrual of resources, including coping resources, which catalyze upward spirals toward future well-being. Initial research supports the tenets of broaden and build; however, few if any, studies have examined this theory with children or adolescents, particularly in the context of school experiences. This study explored the role of positive emotions during school, coping, and student engagement among a sample of 293 students in grades 7 to 10. As expected, frequent positive emotions during school were associated with higher levels of student engagement and negative emotions with lower levels of engagement. Positive emotions, but not negative emotions, were associated with adaptive coping, which was then associated with student engagement. The association between positive emotions and engagement was partially mediated by adaptive coping. Results support the broaden and build theory and the role of positive emotions in students' engagement at school and with learning. Implications and future directions for research are discussed. © 2008 Wiley Periodicals, Inc.