To avoid molecular damage of biomolecules due to oxidation, all cells have evolved constitutive and responsive systems to mitigate and repair chemical modifications. Archaea have adapted to some of the most extreme environments known to support life, including highly oxidizing conditions. However, in comparison to bacteria and eukaryotes, relatively little is known about the biology and biochemistry of archaea in response to changing conditions and repair of oxidative damage. In this study transcriptome, proteome, and chemical reactivity analyses of hydrogen peroxide (H2O2) induced oxidative stress in Sulfolobus solfataricus (P2) were conducted. Microarray analysis of mRNA expression showed that 102 transcripts were regulated by at least 1.5 fold, 30 minutes after exposure to 30 µM H2O2. Parallel proteomic analyses using two-dimensional differential gel electrophoresis (2D-DIGE), monitored more than 800 proteins 30 and 105 minutes after exposure and found that 18 had significant changes in abundance. A recently characterized ferritin-like antioxidant protein, DPSL, was the most highly regulated species of mRNA and protein, in addition to being post-translationally modified. As expected, a number of antioxidant related mRNAs and proteins were differentially regulated. Three of these, DPSL, superoxide dismutase, and peroxiredoxin were shown to interact and likely form a novel supramolecular complex for mitigating oxidative damage. A scheme for the ability of this complex to perform multi-step reactions is presented. Despite the central role played by DPSL, cells maintained a lower level of protection after disruption of the dpsl gene, indicating a level of redundancy in the oxidative stress pathways of S. solfataricus. This work provides the first “omics” scale assessment of the oxidative stress response for an archeal organism and together with a network analysis using data from previous studies on bacteria and eukaryotes reveals evolutionarily conserved pathways where complex and overlapping defense mechanisms protect against oxygen toxicity.

Ecosystem energy is now recognized as a primary correlate and potential driver of global patterns of species richness. The increasingly well-tested species-energy relationship is now ripe for application to conservation, and recent advances in satellite technology make this more feasible. While the correlates for the species-energy relationship have been addressed many times previously, this study is among the first to apply species-energy theory to conservation. Our objectives were to: (1) determine the strongest model of bird richness across North America; (2) determine whether the slope of the best species-energy model varied with varying energy levels; and (3) identify the spatial patterns with similar or dissimilar slopes to draw inference for conservation. Model selection techniques were used to evaluate relationships between Moderate Resolution Imaging Spectroradiometer (MODIS) measures of ecosystem energy and species richness of native land birds using the USGS Breeding Bird Survey (BBS) data. Linear, polynomial, and break point regression techniques were used to evaluate the shape of the relationships with correction for spatial autocorrelation. Spatial analyses were used to determine regions where slopes of the relationship differed. We found that annual gross primary production (GPP) was the strongest correlate of richness (adjusted R2 = 0.55), with a quadratic model being the strongest model. The negative slope of the model was confirmed significantly negative at the highest energy levels. This finding demonstrates that there are three different slopes to the species-energy relationship across the energy gradient of North America: positive, flat, and negative. If energy has a causal relationship with richness, then species-energy theory implies that energy causes richness to increase in low-energy areas, energy has little effect in intermediate-energy areas, and energy depresses richness in the highest-energy areas. This information provides a basis for potential applications for more effective conservation. For example, in low-energy areas, increased nutrients could improve vegetation productivity and increase species richness. In high-energy areas where competitive dominance of vegetation might reduce species richness, vegetation manipulation could increase species richness. These strategies will likely be most effective if tailored to the local energy gradient.

Quaking aspen (Populus tremuloides Michx.) recruitment and overstory stem densities were sampled in 315 clones in 1991 and 2006 on 560 km 2 of the Northern Yellowstone Winter Range (NYWR). A primary objective was to observe if aspen status had improved from 1991 to 2006: evidence of a wolf (Canis lupus) caused trophic cascade. Recruitment stems (height. 2 m and diameter at breast height , 5 cm) represent recent growth of aspen sprouts above elk (Cervus elaphus) browsing height, whereas overstory stems (all stems. 2 m) represent the cohort of stems, which will insure the sustainability of the clone. Overstory stem densities declined by 12% (P 5 0.04) on the landscape scale when compared with paired t-tests. Overstory stems declined in 58% of individual clones and in 63% of the 24 drainages of the study area. The second objective was to determine which factors influenced changes in aspen density. Winter ungulate browsing (P 5 0.0001), conifer establishment (P 5 0.0001), and cattle (Bos spp.) grazing (P 5 0.016) contributed to the decline in overstory stem densities when analyzed using a mixed effects model of log transformed medians. Eighty percent of the clones were classified as having medium to high browsing levels in 1991, whereas 65% of the clones received a similar rating in 2006, possibly due to the reduced NYWR elk population. Aspen recruitment has increased in some 2-10 km 2 areas, but not consistently. Our study found that a trophic cascade of wolves, elk, and aspen, resulting in a landscape-level recovery of aspen, is not occurring at this time. Resumen Se muestreó el reclutamiento y la densidad de tallos aéreos de Populus tremuloides Michx. de 315 clones en 1991 y 2006 en un área de 560 km 2 en la Invernada Norte de Yellowstone (NYWR). Un objetivo primario de este estudio fue observar si el estatus de P. tremuloides mejoró entre 1991 y 2006 evidenciando una cascada trófica causada por el lobo (Canis lupus). El reclutamiento de tallos nuevos (altura. 2 m y diámetro a la altura del pecho , 5 cm) representa crecimiento de brotes recientes por encima de la línea de ramoneo de los ciervos (Cervus elaphus), mientras que los tallos aéreos (todos los tallos. 2 m) representan la cohorte de tallos que asegurarán la sustentabilidad del clon. Las densidades de tallos aéreos decreció en un 12% (P 5 0.04) a la escala de paisaje según una comparación realizada con un prueba de ''t'' apareada. Los tallos aéreos decrecieron en un 58% de los clones individuales y en un 63% de las 24 micro-cuencas del área de estudio. El segundo objetivo de este estudio fue determinar cuáles factores influenciaron los cambios en la densidad de P. tremuloides. El ramoneo invernal de los ungulados (P 5 0.0001), el establecimiento de coníferas (P 5 0.0001), y el pastoreo bovino (Bos spp.; P 5 0.016) contribuyeron a la disminución en la densidad de tallos aéreos según un análisis de efectos mixtos utilizando una transformación logarítmica de las medianas. El 80% de los clones fueron clasificados en la categoría de nivel de uso medio a elevado...

Aim To demonstrate that the concept of carrying capacity for species richness (SK) is highly relevant to the conservation of biodiversity, and to estimate the spatial pattern of SK for native landbirds as a basis for conservation planning.Location North America. MethodsWe evaluated the leading hypotheses on biophysical factors affecting species richness for Breeding Bird Survey routes from areas with little influence of human activities. We then derived a best model based on information theory, and used this model to extrapolate SK across North America based on the biophysical predictor variables. The predictor variables included the latest and probably most accurate satellite and simulation-model derived products. ResultsThe best model of SK included mean annual and inter-annual variation in gross primary productivity and potential evapotranspiration. This model explained 70% of the variation in landbird species richness. Geographically, predicted SK was lowest at higher latitudes and in the arid west, intermediate in the Rocky Mountains and highest in the eastern USA and the Great Lakes region of the USA and Canada. Main conclusionsAreas that are high in SK but low in human density are high priorities for protection, and areas high in SK and high in human density are high priorities for restoration. Human density was positively related to SK, indicating that humans select environments similar to those with high bird species richness. Federal lands were disproportionately located in areas of low predicted SK.

No abstract