Land-Use Changes in Southern Appalachian Landscapes: Spatial Analysis and Forecast Evaluation

Understanding human disturbance regimes is crucial for developing effective conservation and ecosystem management plans and for targeting ecological research to areas that define scarce ecosystem services. We evaluate and develop a forecasting model for land-use change in the Southern Appalachians. We extend previous efforts by (a) addressing the spatial diffusion of human populations, approximated by building density, (b) examining a long time period (40 years, which is epochal in economic terms), and (c) explicitly testing the forecasting power of the models. The resulting model, defined by linking a negative binomial regression model of building density with a logit model of land cover, was fit using spatially referenced data from four study sites in the Southern Appalachians. All fitted equations were significant, and coefficient estimates indicated that topographic features as well as location significantly shape population diffusion and land use across these landscapes. This is especially evident in the study sites that have experienced development pressure over the last 40 years. Model estimates also indicate significant spatial autocorrelation in land-use observations. Forecast performance of the models was evaluated by using a separate validation data set for each study area. Depending on the land-use classification scheme, the models correctly predicted between 68% and 89% of observed land uses. Tests based on information theory reject the hypothesis that the models have no explanatory power, and measures of entropy and information gain indicate that the estimated models explain between 47% and 66% of uncertainty regarding land-use classification. Overall, these results indicate that modeling land-cover change alone may not be useful over the long run, because changing land cover reflects the outcomes of more than one human process (for example, agricultural decline and population growth). Here, additional information was gained by addressing the spatial spread of human populations. Furthermore, coarse-scale measures of the human drivers of landscape change (for example, population growth measured at the county level) appear to be poor predictors of changes realized at finer scales. Simulations demonstrate how this type of approach might be used to target scarce resources for conservation and research efforts into ecosystem effects. Received 13 March 1998; accepted 30 September 1998     

Creating difficulties everywhere

In this essay we link the rationale for the medical humanities with radical hermeneutics, a move that infuses the medical humanities with incredulity and suspicion. This orientation is particularly important at this historical moment, when the evidence-based and competency blanket is threatening to overpower all aspects of medical education, including the medical humanities discourse itself. Radical hermeneutics works relentlessly against the final word on anything, and as such, it provides a critically provocative way of thinking about doctors, patients, illness, health, families, death--in short, the experience of being human. We use three literary examples to illustrate the complex, contradictory, perplexing, and disturbing questions related to a life in medicine: Rafael Campo's "Like a Prayer," Irvin Yalom's "Fat Lady," and Richard Selzer's "Brute."     

Draft genome sequence of marine alphaproteobacterial strain HIMB11, the first cultivated representative of a unique lineage within the Roseobacter clade possessing an unusually small genome

Strain HIMB11 is a planktonic marine bacterium isolated from coastal seawater in Kaneohe Bay, Oahu, Hawaii belonging to the ubiquitous and versatile Roseobacter clade of the alphaproteobacterial family Rhodobacteraceae. Here we describe the preliminary characteristics of strain HIMB11, including annotation of the draft genome sequence and comparative genomic analysis with other members of the Roseobacter lineage. The 3,098,747 bp draft genome is arranged in 34 contigs and contains 3,183 protein-coding genes and 54 RNA genes. Phylogenomic and 16S rRNA gene analyses indicate that HIMB11 represents a unique sublineage within the Roseobacter clade. Comparison with other publicly available genome sequences from members of the Roseobacter lineage reveals that strain HIMB11 has the genomic potential to utilize a wide variety of energy sources (e.g. organic matter, reduced inorganic sulfur, light, carbon monoxide), while possessing a reduced number of substrate transporters.     

Molecular basis for Cdk1‐regulated timing of Mis18 complex assembly and CENP‐A deposition

The centromere, a chromosomal locus that acts as a microtubule attachment site, is epigenetically specified by the enrichment of CENP‐A nucleosomes. Centromere maintenance during the cell cycle requires HJURP‐mediated CENP‐A deposition, a process regulated by the Mis18 complex (Mis18α/Mis18β/Mis18BP1). Spatial and temporal regulation of Mis18 complex assembly is crucial for its centromere association and function. Here, we provide the molecular basis for the assembly and regulation of the Mis18 complex. We show that the N‐terminal region of Mis18BP1 spanning amino acid residues 20–130 directly interacts with Mis18α/β to form the Mis18 complex. Within Mis18α/β, the Mis18α MeDiY domain can directly interact with Mis18BP1. Mis18α/β forms a hetero‐hexamer with 4 Mis18α and 2 Mis18β. However, only two copies of Mis18BP1 interact with Mis18α/β to form a hetero‐octameric assembly, highlighting the role of Mis18 oligomerization in limiting the number of Mis18BP1 within the Mis18 complex. Furthermore, we demonstrate the involvement of consensus Cdk1 phosphorylation sites on Mis18 complex assembly and thus provide a rationale for cell cycle‐regulated timing of Mis18 assembly and CENP‐A deposition.     

Investigation of core machinery for biosynthesis of Vi antigen capsular polysaccharides in Gram-negative bacteria

Salmonella enterica serovar Typhi causes typhoid fever. It possesses a Vi antigen capsular polysaccharide coat that is important for virulence and is the basis of a current glycoconjugate vaccine. Vi antigen is also produced by environmental Bordetella isolates, while mammal-adapted Bordetella species (such as Bordetella bronchiseptica) produce a capsule of undetermined structure that cross-reacts with antibodies recognizing Vi antigen. The Vi antigen backbone is composed of poly-α-(1→4)-linked N-acetylgalactosaminuronic acid, modified with O-acetyl residues that are necessary for vaccine efficacy. Despite its biological and biotechnological importance, some central aspects of Vi antigen production are poorly understood. Here we demonstrate that TviE and TviD, two proteins encoded in the viaB (Vi antigen production) locus, interact and are the Vi antigen polymerase and O-acetyltransferase, respectively. Structural modeling and site-directed mutagenesis reveal that TviE is a GT4-family glycosyltransferase. While TviD has no identifiable homologs beyond Vi antigen systems in other bacteria, structural modeling suggests that it belongs to the large SGNH hydrolase family, which contains other O-acetyltransferases. Although TviD possesses an atypical catalytic triad, its O-acetyltransferase function was verified by antibody reactivity and ¹³C NMR data for tviD-mutant polysaccharide. The B. bronchiseptica genetic locus predicts a mode of synthesis distinct from classical S. enterica Vi antigen production, but which still involves TviD and TviE homologs that are both active in a reconstituted S. Typhi system. These findings provide new insight into Vi antigen production and foundational information for the glycoengineering of Vi antigen production in heterologous bacteria.