Linking Industrial Ecology and Ecological Economics: A Theoretical and Empirical Foundation for the Circular Economy

The circular economy (CE) is a new model for the production and consumption of goods, which has attracted wide political attention as a strategy toward sustainability. However, the theoretical foundation of CE remains poorly structured and insufficiently explored. Recent studies have shown that the CE model draws on different schools of thought and that its origins are mainly rooted in fields such as industrial ecology (IE) and ecological economics (EE). In this article, we investigate the links between CE, IE, and EE and provide an overview of the similarities and differences between these fields. At the same time, we analyze to what extent the linkages between IE and EE can create a coherent body of knowledge for CE, and be used to identify further research opportunities. This paper shows that, until now, research on CE seems to be mainly rooted in the field of IE and based on concepts and tools that already exist in other fields, rather than inventing new ones. The reconciliation of IE and EE could provide a mechanism to extend beyond such a narrow focus, and increase knowledge of the theoretical and practical framework of CE to benefit sustainability.     

Sociocultural Factors and School Engagement Among African American Youth: The Roles of Racial Discrimination,Racial Socialization,and Ethnic Identity

This study investigated the links between racial discrimination and school engagement and the roles of racial socialization and ethnic identity as protective factors in those linkages in a sample of 148, sixth through twelfth grade African American adolescents from working and middle-class two-parent families. In home interviews, youth described their ethnic identity, discrimination experiences at school, and school engagement (school bonding, school grades, school self-esteem), and parents rated their racial socialization practices. Analyses revealed that discrimination was negatively related to school self-esteem and school bonding. Racial socialization had additive effects on school self-esteem and school bonding, but did not moderate the discrimination—school engagement association. For boys, ethnic identity had additive effects on school bonding, but for girls, ethnic identity moderated the relation between discrimination and school bonding: when girls experienced more discrimination and had a lower ethnic identity, they reported lower school bonding. Discrimination, racial socialization, and ethnic identity were not related to school grades.     

Linking Research to the Practice of Youth Development

The articles in this special issue address some of the challenges of strengthening the links between research and the practice of youth development and identify some approaches that have worked well. Youth development emerged from practice rather than from theory or research. Research that is most useful in the practice of youth development honors that primacy both by exploring questions that are important in practice and by engaging practitioners as partners, not merely as consumers.     

American Indians with African Ancestry: Differential Fertility and the Complexities of Social Identity

Interethnic marriage represents a major trend in the demographic history of American Indians. While the majority of these unions involved Indian women and Caucasian men, a sizeable number occurred between Indians and African Americans. The children of these bicultural marriages were “mixed bloods” who in turn typically married non-Indians or other mixed bloods. Using data from the 1910 Census on American Indians in the United States and Alaska, this article explores why American Indians with African ancestry enjoyed high fertility. Differential rates of fertility among American Indians in the past were due to a number of underlying genetic, cultural, and environmental factors. By identifying these factors, the paradox of why Indian women with African heritage did so well in terms of fertility largely disappears. African admixture, however, greatly complicates Indian social identity.     

Patterns and Processes of Genome-Wide Divergence Between North American and African Drosophila melanogaster

Genomic tools and analyses are now being widely used to understand genome-wide patterns and processes associated with speciation and adaptation. In this article, we apply a genomics approach to the model organism Drosophila melanogaster. This species originated in Africa and subsequently spread and adapted to temperate environments of Eurasia and the New World, leading some populations to evolve reproductive isolation, especially between cosmopolitan and Zimbabwean populations. We used tiling arrays to identify highly differentiated regions within and between North America (the United States and Caribbean) and Africa (Cameroon and Zimbabwe) across 63% of the D. melanogaster genome and then sequenced representative fragments to study their genetic divergence. Consistent with previous findings, our results showed that most differentiation was between populations living in Africa vs. outside of Africa (i.e., “out-of-Africa” divergence), with all other geographic differences being less substantial (e.g., between cosmopolitan and Zimbabwean races). The X chromosome was much more strongly differentiated than the autosomes between North American and African populations (i.e., greater X divergence). Overall differentiation was positively associated with recombination rates across chromosomes, with a sharp reduction in regions near centromeres. Fragments surrounding these high F_ST sites showed reduced haplotype diversity and increased frequency of rare and derived alleles in North American populations compared to African populations. Nevertheless, despite sharp deviation from neutrality in North American strains, a small set of bottleneck/expansion demographic models was consistent with patterns of variation at the majority of our high F_ST fragments. Although North American populations were more genetically variable compared to Europe, our simulation results were generally consistent with those previously based on European samples. These findings support the hypothesis that most differentiation between North America and Africa was likely driven by the sorting of African standing genetic variation into the New World via Europe. Finally, a few exceptional loci were identified, highlighting the need to use an appropriate demographic null model to identify possible cases of selective sweeps in species with complex demographic histories.THE study of genetic differentiation between populations and species has recently been empowered by the use of genomic techniques and analysis (e.g., Noor and Feder 2006; Stinchcombe and Hoekstra 2008). In the past decade, genetic studies of adaptation and speciation have taken advantage of emerging molecular techniques to scan the genomes of diverging populations for highly differentiated genetic regions (e.g., Wilding et al. 2001; Emelianov et al. 2003; Beaumont and Balding 2004; Campbell and Bernatchez 2004; Scotti-Saintagne et al. 2004; Achere et al. 2005; Turner et al. 2005; Vasemagi et al. 2005; Bonin et al. 2006, 2007; Murray and Hare 2006; Savolainen et al. 2006; Yatabe et al. 2007; Nosil et al. 2008, 2009; Turner et al. 2008a,b; Kulathinal et al. 2009). As a result, genome scans can identify candidate regions that may be associated with adaptive evolution between diverging populations and, more broadly, are able to describe genome-wide patterns and processes of population differentiation (Begun et al. 2007; Stinchcombe and Hoekstra 2008).Genome scans in well-studied genetic model species such as Drosophila melanogaster gain particular power because differentiated loci are mapped to a well-annotated genome. Moreover, the evolutionary history of D. melanogaster is rich with adaptive and demographic events with many parallels to human evolution. Most notable is the historical out-of-Africa migration and subsequent adaptation to temperate ecological environments of Europe, Asia, North America, and Australia. This has resulted in widespread genetic and phenotypic divergence between African and non-African populations (e.g., David and Capy 1988; Begun and Aquadro 1993; Capy et al. 1994; Colegrave et al. 2000; Rouault et al. 2001; Takahashi et al. 2001; Caracristi and Schlötterer 2003; Baudry et al. 2004; Pool and Aquadro 2006; Schmidt et al. 2008; Yukilevich and True 2008a,b). Further, certain populations in Africa and in the Caribbean vary in their degree of reproductive isolation from populations in more temperate regions (Wu et al. 1995; Hollocher et al. 1997; Yukilevich and True 2008a,b). In particular, the Zimbabwe and nearby populations of southern Africa are strongly sexually isolated from all other populations, designating them as a distinct behavioral race (Wu et al. 1995).D. melanogaster has received a great deal of attention from the population geneticists in studying patterns of sequence variation across African and non-African populations. Many snapshots have been taken of random microsatellite and SNP variants spread across X and autosomes, and these have generated several important conclusions. Polymorphism patterns in European populations are characterized by reduced levels of nucleotide and haplotype diversity, an excess of high frequency-derived polymorphisms, and elevated levels of linkage disequilibrium relative to African populations (e.g., Begun and Aquadro 1993; Andolfatto 2001; Glinka et al. 2003; Haddrill et al. 2005; Ometto et al. 2005; Thornton and Andolfatto 2006; Hutter et al. 2007; Singh et al. 2007). These results have been generally interpreted as compatible with population size reduction/bottlenecks followed by recent population expansions. On the other hand, African populations are generally assumed either to have been relatively constant in size over time or to have experienced population size expansions. They generally show higher levels of nucleotide and haplotype diversity, an excess of rare variants, and a deficit of high frequency-derived alleles (Glinka et al. 2003; Ometto et al. 2005; Pool and Aquadro 2006; Hutter et al. 2007; but see Haddrill et al. 2005 for evidence of bottlenecks in Africa).Previous work also shows that the ratio of X-linked to autosomal polymorphism deviates from neutral expectations in opposite directions in African and European populations with more variation on the X than expected in Africa and less variation on the X than expected in Europe (Andolfatto 2001; Kauer et al. 2002; Hutter et al. 2007; Singh et al. 2007). The deviation from neutrality in the ratio of X-autosome polymorphism may be explained by positive selection being more prevalent on the X in Europe and/or by a combination of bottlenecks and male-biased sex ratios in Europe and female-biased sex ratios in Africa (Charlesworth 2001; Hutter et al. 2007; Singh et al. 2007). The selective explanation stems from the argument that, under the hitchhiking selection model, X-linked loci are likely to be more affected by selective sweeps than autosomal loci (Maynard Smith and Haigh 1974; Charlesworth et al. 1987; Vicoso and Charlesworth 2006, 2009).The relative contribution of selective and demographic processes in shaping patterns of genomic variation and differentiation is highly debated (Wall et al. 2002; Glinka et al. 2003; Haddrill et al. 2005; Ometto et al. 2005; Schöfl and Schlötterer 2004; Thornton and Andolfatto 2006; Hutter et al. 2007; Singh et al. 2007; Shapiro et al. 2007; Stephan and Li 2007; Hahn 2008; Macpherson et al. 2008; Noor and Bennett 2009; Sella et al. 2009). This is especially the case in D. melanogaster because derived non-African populations have likely experienced a complex set of demographic events during their migration out of Africa (e.g., Thornton and Andolfatto 2006; Singh et al. 2007; Stephan and Li 2007), making population genetics signatures of demography and selection difficult to tease apart (e.g., Macpherson et al. 2008). Thus it is still unclear what role selection has played in shaping overall patterns of genomic variation and differentiation relative to demographic processes in this species.While there is a long tradition in studying arbitrarily or opportunistically chosen sequences in D. melanogaster, genomic scans that focus particularly on highly differentiated sites across the genome have received much less attention. Such sites are arguably the best candidates to resolve the debate on which processes have shaped genomic differentiation within species (e.g., Przeworski 2002). Recently, a genome-wide scan of cosmopolitan populations in the United States and in Australia was performed to investigate clinal genomic differentiation on the two continents (Turner et al. 2008a). Many single feature polymorphisms differentiating Northern and Southern Hemisphere populations were identified. Among the most differentiated loci in common between continents, 80% were differentiated in the same orientation relative to the Equator, implicating selection as the likely explanation (Turner et al. 2008a). Larger regions of genomic differentiation within and between African and non-African populations have also been discovered, some of them possibly being driven by divergent selection (e.g., Dopman and Hartl 2007; Emerson et al. 2008; Turner et al. 2008a, Aguade 2009). Despite this recent progress, we still know relatively little about large-scale patterns of genomic differentiation in this species, especially between African and non-African populations, and whether most of this differentiation is consistent with demographic processes alone or if it requires selective explanations.In this work, we explicitly focus on identifying differentiated sites across the genome between U.S., Caribbean, West African, and Zimbabwean populations. This allows us to address several fundamental questions related to genomic evolution in D. melanogaster, such as the following: (1) Do genome-wide patterns of differentiation reflect patterns of reproductive isolation? (2) Is genomic differentiation random across and within chromosomes or are some regions overrepresented? (3) What are the population genetics properties of differentiated sites and their surrounding sequences? (4) Can demographic historical processes alone explain most of the observed differentiation on a genome-wide level or is it necessary to involve selection in their explanation?In general, our findings revealed that most genomic differentiation within D. melanogaster shows an out-of-Africa genetic signature. These results are inconsistent with the notion that most genomic differentiation occurs between cosmopolitan and Zimbabwean reproductively isolated races. Further, we found that the X is more differentiated between North American and African populations and more strongly deviates from pure neutrality in North American populations relative to autosomes. Nevertheless, our article shows that much of this deviation from neutrality is broadly consistent with several demographic null models, with a few notable exceptions. Athough this does not exclude selection as a possible alternative mechanism for the observed patterns, it supports the idea that most differentiation in D. melanogaster was likely driven by the sorting of African standing genetic variation into the New World.     

“Remapping the Fabric of the African Self: A Synoptic Theory”

A thorough knowledge of the synoptic structure and contents of the modern African self is essential for an improved understanding of the Africa of the 21st century. This lack has compelled practitioners to continue to use the Western model of the self as a substitute for the African perspective. This situation is, however, regrettable, since the Western notion of the self is largely incompatible with the African view. The Western model is based on the notion of the self as a demarcated entity set off against the world, whereas the African views the self as an entity in close interaction with the multi-faceted aspects of his world. This paper is an attempt to correct this imbalance. It offers a synoptic theory of the fabric of the modern African self.     

Bridging Multiple Worlds: How African American and Latino Youth in Academic Outreach Programs Navigate Math Pathways to College

Universities have launched outreach programs to enhance their ethnic diversity, yet little developmental research examines students' pathways to college. This study compares capital models (highlighting family background) with challenge models (highlighting students' challenges and resources) in predicting pathways to college. The Bridging Multiple Worlds Model frames this longitudinal study of 120 African American and Latino youth in outreach programs. We examined students' family backgrounds; challenges and resources across family, school, peer, and community worlds; and high school math pathways as predictors of college eligibility and enrollment. African American students more typically had U. S. born, college-educated parents, and Latino students, immigrant parents with high school education or less. Second, students saw parents as greater resources than teachers, siblings, and themselves; peers and teachers were their greatest challenges. Youth distinguished resources and challenges more by their source than form. Third, high school math and English grades rose and fell together, with early math grades predicting college eligibility. Five math pathways emerged: steady, slowly declining, rapidly declining, increasing, and "back on track" toward college, but pathways did not always predict college choices. Fourth, although family background predicted few outcomes, parents' and teachers' help and siblings' challenges predicted grades, eligibility, and admission to prestigious colleges. Findings highlight both capital and challenge models for science, policy, and programs involving diversity and equity.     

Gun Possession among American Youth: A Discovery-Based Approach to Understand Gun Violence

Objective

To apply discovery-based computational methods to nationally representative data from the Centers for Disease Control and Preventions’ Youth Risk Behavior Surveillance System to better understand and visualize the behavioral factors associated with gun possession among adolescent youth.

Results

Our study uncovered the multidimensional nature of gun possession across nearly five million unique data points over a ten year period (2001–2011). Specifically, we automated odds ratio calculations for 55 risk behaviors to assemble a comprehensive table of associations for every behavior combination. Downstream analyses included the hierarchical clustering of risk behaviors based on their association “fingerprint” to 1) visualize and assess which behaviors frequently co-occur and 2) evaluate which risk behaviors are consistently found to be associated with gun possession. From these analyses, we identified more than 40 behavioral factors, including heroin use, using snuff on school property, having been injured in a fight, and having been a victim of sexual violence, that have and continue to be strongly associated with gun possession. Additionally, we identified six behavioral clusters based on association similarities: 1) physical activity and nutrition; 2) disordered eating, suicide and sexual violence; 3) weapon carrying and physical safety; 4) alcohol, marijuana and cigarette use; 5) drug use on school property and 6) overall drug use.

Conclusions

Use of computational methodologies identified multiple risk behaviors, beyond more commonly discussed indicators of poor mental health, that are associated with gun possession among youth. Implications for prevention efforts and future interdisciplinary work applying computational methods to behavioral science data are described.     

Editors' Introduction: Pathways to Identity and Positive Development Among Muslim Youth in the West

The present study used a person-centered approach to examine patterns of conflict experience among 198 3rd–6th grade children. Peer reports of aggressive behavior, sociability, victimization, and an assessment of psychological mindedness in narrative accounts of conflict experiences were used. Three patterns were identified using mixture modeling: Managers, Avoiders, and Sustainers. Patterns differed with respect to narrative skills and social adjustment. Findings demonstrate the benefit of examining children's ability to tell their own stories in combination with peer perceptions of children's behavior. Discussion focuses on how children may rely on behavioral and narrative skills to develop different ways of responding to peer conflict in context, as well as on the application of findings in school settings.     

Linking Community and Ecosystem Processes: The Role of Minor Species

The link between species and ecosystem functioning is a central issue in ecology. In natural plant communities, the dominant species determine most of the productivity-related processes but what is the function of minor species? A recent hypothesis suggests that after disturbance, minor species facilitate the recruitment and abundance of dominants during re-colonization, thus indirectly determining ecosystem function. We tested this hypothesis using a long-term dataset of annual plant communities in a semiarid shrubland by comparing plant density and biomass from plots in which all vegetation had been removed; plots from which only the dominant (the annual grass Stipa capensis) had been removed, and control plots. In the absence of vegetation, the dominant failed to re-establish during the following growing season. After being removed the dominant re-established similarly to the controls. An ant exclosure experiment excluded the possibility that this was due to seed predation. In an experiment with individual dispersal units of S. capensis, we demonstrated the mechanism by which minor species can control the dominant’s abundance. Minor species indirectly govern ecosystem processes by providing structures facilitating seed soil penetration and thus recruitment of the dominant.     

The Center for Epidemiologic Studies Depression Scale: A Review with a Theoretical and Empirical Examination of Item Content and Factor Structure

Background

The Center for Epidemiologic Studies Depression Scale (CES-D; Radloff, 1977) is a commonly used freely available self-report measure of depressive symptoms. Despite its popularity, several recent investigations have called into question the robustness and suitability of the commonly used 4-factor 20-item CES-D model. The goal of the current study was to address these concerns by confirming the factorial validity of the CES-D.

Methods and Findings

Differential item functioning estimates were used to examine sex biases in item responses, and confirmatory factor analyses were used to assess prior CES-D factor structures and new models heeding current theoretical and empirical considerations. Data used for the analyses included undergraduate (n = 948; 74% women), community (n = 254; 71% women), rehabilitation (n = 522; 53% women), clinical (n = 84; 77% women), and National Health and Nutrition Examination Survey (NHANES; n = 2814; 56% women) samples. Differential item functioning identified an item as inflating CES-D scores in women. Comprehensive comparison of the several models supported a novel, psychometrically robust, and unbiased 3-factor 14-item solution, with factors (i.e., negative affect, anhedonia, and somatic symptoms) that are more in line with current diagnostic criteria for depression.

Conclusions

Researchers and practitioners may benefit from using the novel factor structure of the CES-D and from being cautious in interpreting results from the originally proposed scale. Comprehensive results, implications, and future research directions are discussed.     

Elevated male European and female African contributions to the genomes of African American individuals

The differential relative contribution of males and females from Africa and Europe to individual African American genomes is relevant to mapping genes utilizing admixture analysis. The assessment of ancestral population contributions to the four types of genomic DNA (autosomes, X and Y chromosomes, and mitochondrial) with their differing modes of inheritance is most easily addressed in males. A thorough evaluation of 93 African American males for 2,018 autosomal single nucleotide polymorphic (SNP) markers, 121 X chromosome SNPs, 10 Y chromosome haplogroups specified by SNPs, and six haplogroup defining mtDNA SNPs is presented. A distinct lack of correlation observed between the X chromosome and the autosomal admixture fractions supports separate treatment of these chromosomes in admixture-based gene mapping applications. The European genetic contributions were highest (and African lowest) for the Y chromosome (28.46%), followed by the autosomes (19.99%), then the X chromosome (12.11%), and the mtDNA (8.51%). The relative order of admixture fractions in the genomic compartments validates previous studies that suggested sex-biased gene flow with elevated European male and African female contributions. There is a threefold higher European male contribution compared with European females (Y chromosome vs. mtDNA) to the genomes of African American individuals meaning that admixture-based gene discovery will have the most power for the autosomes and will be more limited for X chromosome analysis. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Ethnic Identity and Positive Youth Development in Adolescent Males: A Culturally Integrated Approach

The present study examined the relation between ethnic identity and indicators of positive youth development (PYD) in a sample of low-income, urban Black and Latino male youth (N = 254; 66% Black, mean age = 14). Using structural equation modeling, a two-factor model of PYD and ethnic identity was found to provide the best fit to the data with a significant, positive relation between the two factors. At age 14, PYD was positively related to concurrent involvement in prosocial activities, and negatively related to criminal and externalizing behaviors; ethnic identity was related to lower levels of internalizing symptoms. The PYD factor was also related to higher prosocial activity involvement and lower criminal offending at age 15. The findings suggest that male Black and Latino teens living in urban poverty have intrapersonal competencies that promote healthy outcomes and that integration of culturally-relevant factors can enhance our understanding of positive youth development.     

An In-Depth Examination of Perceptions of Physical Activity in Regularly Active and Insufficiently Active Older African American Women: A Participatory Approach

Despite considerable research and programmatic efforts to alleviate racial/ethnic disparities in physical activity (PA), disparities in PA among older minorities and major racial ethnic groups persist. This study explored perceptions of PA among regularly active (RA) and insufficiently active (IA) older African American women (AAW) and the factors that influence (positively and negatively) their physical participation in their socio-cultural environment. A total of 20 AAW aged 60 to 80 years participated in a cross-sectional mixed-methods study (i.e., qualitative and quantitative) employing participatory research approaches (i.e., photoelicitation) along with an objective assessment of PA. Nine women were considered RA and 11 IA according to current PA recommendations. RA and IA women held two major beliefs about the nature of PA (i.e., PA as a broadly defined construct that goes beyond traditional exercise routines; and PA and exercise are synonymous and can be used interchangeably) and had a good understanding of its benefits. Participants in both groups did not know about the importance of PA intensity for health benefits. Barriers and facilitator of PA were found to be similar among RA and IA participants. Special attention should be paid to providing access to no or low cost opportunities for PA participation in safe environments.     

When and What Parents Tell Children About Race: An Examination of Race-Related Socialization Among African American Families

This article describes a developmental systems approach to applied developmental science (ADS), which provides a framework to design and evaluate technology-rich programs that promote positive development by emphasizing the strengths and assets of young people instead of focusing on diminishing or preventing risk-taking behaviors. Until now, most of the psychoeducational programs conceived within the ADS model have not focused on the role of new technologies in young people's lives. This absence is particularly striking given that, in today's world, new technologies play an important role in different areas of the lives of young people, such as education, entertainment, socialization, and communication. This article presents the concept of identity construction environments (ICE), an interdisciplinary model that proposes guidelines to design and study new technologies purposefully created to promote positive youth development (PYD). Two types of ICE have been developed: one focusing on stand-alone technologies for learning, such as the Zora virtual city; and the other focusing on an approach for developing technologically rich learning contexts, such as the Project Inter-Actions robotics workshops. This article presents both examples of ICE and describes how their design fosters the 6 components of PYD. Initial findings from pilot studies conducted with very different populations of youth engaged in both types of ICE—such as young children, adolescents, and chronically ill children—are presented.     

Muslim Youth in Canadian Schools: Education and the Politics of Religious Identity

This article provides an ethnographic analysis of the schooling experiences of Muslim youth in Canada who are committed to maintaining an Islamic lifestyle despite the pressures of conformity to the dominant culture. Little attention has been paid to how religious identity intersects with other forms of social difference, such as race and gender in the schooling experiences of minoritized youth. Using a case study often Muslim students and parents, this article demonstrates how Muslim students were able to negotiate and maintain their religious identities within secular public schools. The participants' narratives address the challenges of peer pressure, racism, and Islamophobia. Their stories reveal how Muslim students are located at the nexus of social difference based on their race, gender, and religious identity. The discussion further explores the dynamics through which these youth were able to negotiate the continuity of their Islamic identity and practices within schools despite the challenges that they faced. Building upon existing theories of identity maintenance and construction, this research demonstrates how the interplay of the core factors of ambivalence, role performance, and interaction and isolation are implicated in the way Muslim students negotiate the politics of religious identity in their schooling experiences.     

The Self Model and the Conception of Biological Identity in Immunology

The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for 60 years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity.     

Susceptibility to glaucoma: differential comparison of the astrocyte transcriptome from glaucomatous African American and Caucasian American donors

Background  

Epidemiological and genetic studies indicate that ethnic/genetic background plays an important role in susceptibility to primary open angle glaucoma (POAG). POAG is more prevalent among the African-descent population compared to the Caucasian population. Damage in POAG occurs at the level of the optic nerve head (ONH) and is mediated by astrocytes. Here we investigated differences in gene expression in primary cultures of ONH astrocytes obtained from age-matched normal and glaucomatous donors of Caucasian American (CA) and African American (AA) populations using oligonucleotide microarrays.     

Linking Microbial and Ecosystem Ecology Using Ecological Stoichiometry: A Synthesis of Conceptual and Empirical Approaches

Currently, one of the biggest challenges in microbial and ecosystem ecology is to develop conceptual models that organize the growing body of information on environmental microbiology into a clear mechanistic framework with a direct link to ecosystem processes. Doing so will enable development of testable hypotheses to better direct future research and increase understanding of key constraints on biogeochemical networks. Although the understanding of phenotypic and genotypic diversity of microorganisms in the environment is rapidly accumulating, how controls on microbial physiology ultimately affect biogeochemical fluxes remains poorly understood. We propose that insight into constraints on biogeochemical cycles can be achieved by a more rigorous evaluation of microbial community biomass composition within the context of ecological stoichiometry. Multiple recent studies have pointed to microbial biomass stoichiometry as an important determinant of when microorganisms retain or recycle mineral nutrients. We identify the relevant cellular components that most likely drive changes in microbial biomass stoichiometry by defining a conceptual model rooted in ecological stoichiometry. More importantly, we show how X-ray microanalysis (XRMA), nanoscale secondary ion mass spectroscopy (NanoSIMS), Raman microspectroscopy, and in situ hybridization techniques (for example, FISH) can be applied in concert to allow for direct empirical evaluation of the proposed conceptual framework. This approach links an important piece of the ecological literature, ecological stoichiometry, with the molecular front of the microbial revolution, in an attempt to provide new insight into how microbial physiology could constrain ecosystem processes.