Hibernation factors directly block ribonucleases from entering the ribosome in response to starvation.

Ribosome hibernation is a universal translation stress response found in bacteria as well as plant plastids. The term was coined almost two decades ago and despite recent insights including detailed cryo-EM structures, the physiological role and underlying molecular mechanism of ribosome hibernation has remained unclear. Here, we demonstrate that Escherichia coli hibernation factors RMF, HPF and RaiA (HFs) concurrently confer ribosome hibernation. In response to carbon starvation and resulting growth arrest, we observe that HFs protect ribosomes at the initial stage of starvation. Consistently, a deletion mutant lacking all three factors (ΔHF) is severely inhibited in regrowth from starvation. ΔHF cells increasingly accumulate 70S ribosomes harbouring fragmented rRNA, while rRNA in wild-type 100S dimers is intact. RNA fragmentation is observed to specifically occur at HF-associated sites in 16S rRNA of assembled 70S ribosomes. Surprisingly, degradation of the 16S rRNA 3'-end is decreased in cells lacking conserved endoribonuclease YbeY and exoribonuclease RNase R suggesting that HFs directly block these ribonucleases from accessing target sites in the ribosome.

Cross-ecosystem carbon flows connecting ecosystems worldwide.

Ecosystems are widely interconnected by spatial flows of material, but the overall importance of these flows relative to local ecosystem functioning remains unclear. Here we provide a quantitative synthesis on spatial flows of carbon connecting ecosystems worldwide. Cross-ecosystem flows range over eight orders of magnitude, bringing between 10-3 and 105 gC m-2 year-1 to recipient ecosystems. Magnitudes are similar to local fluxes in freshwater and benthic ecosystems, but two to three orders of magnitude lower in terrestrial systems, demonstrating different dependencies on spatial flows among ecosystem types. The strong spatial couplings also indicate that ecosystems are vulnerable to alterations of cross-ecosystem flows. Thus, a reconsideration of ecosystem functioning, including a spatial perspective, is urgently needed.

Impact of winter roads on boreal peatland carbon exchange.

Across Canada's boreal forest, linear disturbances, including cutlines such as seismic lines and roads, crisscross the landscape to facilitate resource exploration and extraction; many of these linear disturbances cross peatland ecosystems. Changes in tree canopy cover and the compression of the peat by heavy equipment alter local thermal, hydrological, and ecological conditions, likely changing carbon exchange on the disturbance, and possibly in the adjacent peatland. We measured bulk density, water table, soil temperature, plant cover, and CO2 and CH4 flux along triplicate transects crossing a winter road through a wooded fen near Peace River, Alberta, Canada. Sample plots were located 1, 5, and 10 m from the road on both sides with an additional three plots on the road. Productivity of the overstory trees, when present, was also determined. The winter road had higher bulk density, shallower water table, higher graminoid cover, and thawed earlier than the adjacent peatland. Tree productivity and CO2 flux varied between the plots, and there was no clear pattern in relation to distance from the road. The plots on the winter road acted as a greater CO2 sink and greater CH4 source compared to the adjacent peatland with plots on the winter road emitting on average (standard error) 479 (138) compared to 41 (10) mg CH4  m-2  day-1 in the adjacent peatland. Considering both gases, global warming potential increased from 70 to 250 g CO2 e m-2  year-1 in the undisturbed area to 2100 g CO2 e m-2  year-1 on the winter road. Although carbon fluxes on any given cutline through peatland will vary depending on level of compaction, line width and vegetation community shifts, the large number of linear disturbances in Canada's boreal forest and slow recovery on peatland ecosites suggest they could represent an important anthropogenic greenhouse gas source.

Evaluating carbon storage, timber harvest, and habitat possibilities for a Western Cascades (USA) forest landscape.

Forest policymakers and managers have long sought ways to evaluate the capability of forest landscapes to jointly produce timber, habitat, and other ecosystem services in response to forest management. Currently, carbon is of particular interest as policies for increasing carbon storage on federal lands are being proposed. However, a challenge in joint production analysis of forest management is adequately representing ecological conditions and processes that influence joint production relationships. We used simulation models of vegetation structure, forest sector carbon, and potential wildlife habitat to characterize landscape-level joint production possibilities for carbon storage, timber harvest, and habitat for seven wildlife species across a range of forest management regimes. We sought to (1) characterize the general relationships of production possibilities for combinations of carbon storage, timber, and habitat, and (2) identify management variables that most influence joint production relationships. Our 160 000-ha study landscape featured environmental conditions typical of forests in the Western Cascade Mountains of Oregon (USA). Our results indicate that managing forests for carbon storage involves trade-offs among timber harvest and habitat for focal wildlife species, depending on the disturbance interval and utilization intensity followed. Joint production possibilities for wildlife species varied in shape, ranging from competitive to complementary to compound, reflecting niche breadth and habitat component needs of species examined. Managing Pacific Northwest forests to store forest sector carbon can be roughly complementary with habitat for Northern Spotted Owl, Olive-sided Flycatcher, and red tree vole. However, managing forests to increase carbon storage potentially can be competitive with timber production and habitat for Pacific marten, Pileated Woodpecker, and Western Bluebird, depending on the disturbance interval and harvest intensity chosen. Our analysis suggests that joint production possibilities under forest management regimes currently typical on industrial forest lands (e.g., 40- to 80-yr rotations with some tree retention for wildlife) represent but a small fraction of joint production outcomes possible in the region. Although the theoretical boundaries of the production possibilities sets we developed are probably unachievable in the current management environment, they arguably define the long-term potential of managing forests to produce multiple ecosystem services within and across multiple forest ownerships.

Carbon sources and trophic relationships of ice seals during recent environmental shifts in the Bering Sea.

Dramatic multiyear fluctuations in water temperature and seasonal sea ice extent and duration across the Bering-Chukchi continental shelf have occurred in this century, raising a pressing ecological question: Do such environmental changes alter marine production processes linking primary producers to upper trophic-level predators? We examined this question by comparing the blubber fatty acid (FA) composition and stable carbon isotope ratios of individual FA (δ¹³CFA) of adult ringed seals (Pusa hispida), bearded seals (Erignathus barbatus), spotted seals (Phoca largha), and ribbon seals (Histriophoca fasciata), collectively known as "ice seals," sampled during an anomalously warm, low sea ice period in 2002-2005 in the Bering Sea and a subsequent cold, high sea ice period in 2007-2010. δ¹³C(FA) values, used to estimate the contribution to seals of carbon derived from sea ice algae (sympagic production) relative to that derived from water column phytoplankton (pelagic production), indicated that during the cold period, sympagic production accounted for 62-80% of the FA in the blubber of bearded seals, 51-62% in spotted seals, and 21-60% in ringed seals. Moreover, the δ¹³CFA values of bearded seals indicated a greater incorporation of sympagic FAs during the cold period than the warm period. This result provides the first empirical evidence of an ecosystem-scale effect of a putative change in sympagic production in the Western Arctic. The FA composition of ice seals showed clear evidence of resource partitioning among ringed, bearded, and spotted seals, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. Despite interannual variability, the FA composition of ringed and bearded seals showed little evidence of differences in diet between the warm and cold periods. The findings that sympagic production contributes significantly to food webs supporting ice seals, and that the contribution apparently is less in warm years with low sea ice, raise an important concern: Will the projected warming and continuing loss of seasonal sea ice in the Arctic, and the associated decline of organic matter input from sympagic production, be compensated for by pelagic production to satisfy both pelagic and benthic carbon and energy needs?

Restoring forest structure and process stabilizes forest carbon in wildfire-prone southwestern ponderosa pine forests.

Changing climate and a legacy of fire-exclusion have increased the probability of high-severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwestern USA. Efforts to reduce high-severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin-only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatment TEC surpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability. NECB in the presence of wildfire showed a similar response to the no-wildfire scenarios: both thin-only and thin and burn treatments increased the C sink. Treatments increased TEC by reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear.

Spatial distribution and variability of carbon storage in different sympodial bamboo species in China.

Selection of tree species is potentially an important management decision for increasing carbon storage in forest ecosystems. This study investigated and compared spatial distribution and variability of carbon storage in 8 sympodial bamboo species in China. The results of this study showed that average carbon densities (CDs) in the different organs decreased in the order: culms (0.4754 g g(-1)) > below-ground (0.4701 g g(-1)) > branches (0.4662 g g(-1)) > leaves (0.4420 g g(-1)). Spatial distribution of carbon storage (CS) on an area basis in the biomass of 8 sympodial bamboo species was in the order: culms (17.4-77.1%) > below-ground (10.6-71.7%) > branches (3.8-11.6%) > leaves (0.9-5.1%). Total CSs in the sympodial bamboo ecosystems ranged from 103.6 Mg C ha(-1) in Bambusa textilis McClure stand to 194.2 Mg C ha(-1) in Dendrocalamus giganteus Munro stand. Spatial distribution of CSs in 8 sympodial bamboo ecosystems decreased in the order: soil (68.0-83.5%) > vegetation (16.8-31.1%) > litter (0.3-1.7%). Total current CS and biomass carbon sequestration rate in the sympodial bamboo stands studied in China is 93.184 × 10(6) Mg C ha(-1) and 8.573 × 10(6) Mg C yr(-1), respectively. The sympodial bamboos had a greater CSs and higher carbon sequestration rates relative to other bamboo species. Sympodial bamboos can play an important role in improving climate and economy in the widely cultivated areas of the world.

The dynamical landscape of marine phytoplankton diversity.

Observations suggest that the landscape of marine phytoplankton assemblage might be strongly heterogeneous at the dynamical mesoscale and submesoscale (10-100 km, days to months), with potential consequences in terms of global diversity and carbon export. But these variations are not well documented as synoptic taxonomic data are difficult to acquire. Here, we examine how phytoplankton assemblage and diversity vary between mesoscale eddies and submesoscale fronts. We use a multi-phytoplankton numerical model embedded in a mesoscale flow representative of the North Atlantic. Our model results suggest that the mesoscale flow dynamically distorts the niches predefined by environmental contrasts at the basin scale and that the phytoplankton diversity landscape varies over temporal and spatial scales that are one order of magnitude smaller than those of the basin-scale environmental conditions. We find that any assemblage and any level of diversity can occur in eddies and fronts. However, on a statistical level, the results suggest a tendency for larger diversity and more fast-growing types at fronts, where nutrient supplies are larger and where populations of adjacent water masses are constantly brought into contact; and lower diversity in the core of eddies, where water masses are kept isolated long enough to enable competitive exclusion.

Mechanisms of piñon pine mortality after severe drought: a retrospective study of mature trees.

Conifers have incurred high mortality during recent global-change-type drought(s) in the western USA. Mechanisms of drought-related tree mortality need to be resolved to support predictions of the impacts of future increases in aridity on vegetation. Hydraulic failure, carbon starvation and lethal biotic agents are three potentially interrelated mechanisms of tree mortality during drought. Our study compared a suite of measurements related to these mechanisms between 49 mature piñon pine (Pinus edulis Engelm.) trees that survived severe drought in 2002 (live trees) and 49 trees that died during the drought (dead trees) over three sites in Arizona and New Mexico. Results were consistent over all sites indicating common mortality mechanisms over a wide region rather than site-specific mechanisms. We found evidence for an interactive role of hydraulic failure, carbon starvation and biotic agents in tree death. For the decade prior to the mortality event, dead trees had twofold greater sapwood cavitation based on frequency of aspirated tracheid pits observed with scanning electron microscopy (SEM), smaller inter-tracheid pit diameter measured by SEM, greater diffusional constraints to photosynthesis based on higher wood δ(13)C, smaller xylem resin ducts, lower radial growth and more bark beetle (Coleoptera: Curculionidae) attacks than live trees. Results suggest that sapwood cavitation, low carbon assimilation and low resin defense predispose piñon pine trees to bark beetle attacks and mortality during severe drought. Our novel approach is an important step forward to yield new insights into how trees die via retrospective analysis.

Quantifying the timescales over which exogenous and endogenous conditions affect soil respiration.

Understanding how exogenous and endogenous factors and above-ground-below-ground linkages modulate carbon dynamics is difficult because of the influences of antecedent conditions. For example, there are variable lags between above-ground assimilation and below-ground efflux, and the duration of antecedent periods are often arbitrarily assigned. Nonetheless, developing models linking above- and below-ground processes is crucial for estimating current and future carbon dynamics. We collected data on leaf-level photosynthesis (Asat ) and soil respiration (Rsoil ) in different microhabitats (under shrubs vs under bunchgrasses) in the Sonoran Desert. We evaluated timescales over which endogenous and exogenous factors control Rsoil by analyzing data in the context of a semimechanistic temperature-response model of Rsoil that incorporated effects of antecedent exogenous (soil water) and endogenous (Asat ) conditions. For both microhabitats, antecedent soil water and Asat significantly affected Rsoil , but Rsoil under shrubs was more sensitive to Asat than that under bunchgrasses. Photosynthetic rates 1 and 3 d before the Rsoil measurement were most important in determining current-day Rsoil under bunchgrasses and shrubs, respectively, indicating a significant lag effect. Endogenous and exogenous controls are critical drivers of Rsoil , but the relative importance and the timescale over which each factor affects Rsoil depends on above-ground vegetation and ecosystem structure characteristics.

Night temperature and source-sink effects on overall growth, cell number and cell size in bell pepper ovaries.

BACKGROUND AND AIMS: Ovary swelling, and resultant fruit malformation, in bell pepper flowers is favoured by low night temperature or a high source-sink ratio. However, the interaction between night temperature and source-sink ratio on ovary swelling and the contribution of cell size and cell number to ovary swelling are unknown. The present research examined the interactive effects of night temperature and source-sink ratio on ovary size, cell number and cell size at anthesis in bell pepper flowers. METHODS: Bell pepper plants were grown in growth chambers at night temperatures of either 20 °C (HNT) or 12 °C (LNT). Within each temperature treatment, plants bore either 0 (non-fruiting) or two developing fruits per plant. Ovary fresh weight, cell size and cell number were measured. KEY RESULTS: Ovary fresh weights in non-fruiting plants grown at LNT were the largest, while fresh weights were smallest in plants grown at HNT with fruits. In general, mesocarp cell size in ovaries was largest in non-fruiting plants grown at either LNT or HNT and smallest in fruiting plants at HNT. Mesocarp cell number was greater in non-fruiting plants under LNT than in the rest of the night temperature/fruiting treatments. These responses were more marked in ovaries sampled after 18 d of treatment compared with those sampled after 40 d of treatment. CONCLUSIONS: Ovary fresh weight of flowers at anthesis increased 65 % in non-fruiting plants grown under LNT compared with fruiting plants grown under HNT. This increase was due primarily to increases in mesocarp cell number and size. These results indicate that the combined effects of LNT and high source-sink ratio on ovary swelling are additive. Furthermore, the combined effects of LNT and low source-sink ratio or HNT and high source-sink ratio can partially overcome the detrimental effects of LNT and high source-sink ratio.

Venation networks and the origin of the leaf economics spectrum.

The leaf economics spectrum describes biome-invariant scaling functions for leaf functional traits that relate to global primary productivity and nutrient cycling. Here, we develop a comprehensive framework for the origin of this leaf economics spectrum based on venation-mediated economic strategies. We define a standardized set of traits - density, distance and loopiness - that provides a common language for the study of venation. We develop a novel quantitative model that uses these venation traits to model leaf-level physiology, and show that selection to optimize the venation network predicts the mean global trait-trait scaling relationships across 2548 species. Furthermore, using empirical venation data for 25 plant species, we test our model by predicting four key leaf functional traits related to leaf economics: net carbon assimilation rate, life span, leaf mass per area ratio and nitrogen content. Together, these results indicate that selection on venation geometry is a fundamental basis for understanding the diversity of leaf form and function, and the carbon balance of leaves. The model and associated predictions have broad implications for integrating venation network geometry with pattern and process in ecophysiology, ecology and palaeobotany.

Rangeomorphs, Thectardis (Porifera?) and dissolved organic carbon in the Ediacaran oceans.

The mid-Ediacaran Mistaken Point biota of Newfoundland represents the first morphologically complex organisms in the fossil record. At the classic Mistaken Point localities the biota is dominated by the enigmatic group of "fractally" branching organisms called rangeomorphs. One of the few exceptions to the rangeomorph body plan is the fossil Thectardis avalonensis, which has been reconstructed as an upright, open cone with its apex in the sediment. No biological affinity has been suggested for this fossil, but here we show that its body plan is consistent with the hydrodynamics of the sponge water-canal system. Further, given the habitat of Thectardis beneath the photic zone, and the apparent absence of an archenteron, movement, or a fractally designed body plan, we suggest that it is a sponge. The recognition of sponges in the Mistaken Point biota provides some of the earliest body fossil evidence for this group, which must have ranged through the Ediacaran based on biomarkers, molecular clocks, and their position on the metazoan tree of life, in spite of their sparse macroscopic fossil record. Should our interpretation be correct, it would imply that the paleoecology of the Mistaken Point biota was dominated by sponges and rangeomorphs, organisms that are either known or hypothesized to feed in large part on dissolved organic carbon (DOC). The biology of these two clades gives insight into the structure of the Ediacaran ocean, and indicates that a non-uniformitarian mechanism delivered labile DOC to the Mistaken Point seafloor.

Production of ectomycorrhizal mycelium peaks during canopy closure in Norway spruce forests.

*Here, species composition and biomass production of actively growing ectomycorrhizal (EM) mycelia were studied over the rotation period of managed Norway spruce (Picea abies) stands in south-western Sweden. *The EM mycelia were collected using ingrowth mesh bags incubated in the forest soil during one growing season. Fungal biomass was estimated by ergosterol analysis and the EM species were identified by 454 sequencing of internal transcribed spacer (ITS) amplicons. Nutrient availability and the fungal biomass in soil samples were also estimated. *Biomass production peaked in young stands (10-30 yr old) before the first thinning phase. Tylospora fibrillosa dominated the EM community, especially in these young stands, where it constituted 80% of the EM amplicons derived from the mesh bags. Species richness increased in older stands. *The establishment of EM mycelial networks in young Norway spruce stands requires large amounts of carbon, while much less is needed to sustain the EM community in older stands. The variation in EM biomass production over the rotation period has implications for carbon sequestration rates in forest soils.

You can get there from here: acetone, anionic ketones and even-carbon fatty acids can provide substrates for gluconeogenesis.

Although the literature contains studies published more than 30 years ago showing that acetone is not metabolically inert, it is common to find biochemistry textbooks and current research publications asserting that acetone is a 'dead-end' metabolite. In fact, acetone derived from the non-enzymatic breakdown of acetoacetate in ketotic individuals or from the oxidation of ingested isopropanol can be metabolized to D-lactate and pyruvate, and ultimately glucose. This report describes the reactions and pathways that account for the metabolism of acetone in humans.

Re-assessment of plant carbon dynamics at the Duke free-air CO(2) enrichment site: interactions of atmospheric [CO(2)] with nitrogen and water availability over stand development.

*The potential for elevated [CO(2)]-induced changes to plant carbon (C) storage, through modifications in plant production and allocation of C among plant pools, is an important source of uncertainty when predicting future forest function. Utilizing 10 yr of data from the Duke free-air CO(2) enrichment site, we evaluated the dynamics and distribution of plant C. *Discrepancy between heights measured for this study and previously calculated heights required revision of earlier allometrically based biomass determinations, resulting in higher (up to 50%) estimates of standing biomass and net primary productivity than previous assessments. *Generally, elevated [CO(2)] caused sustained increases in plant biomass production and in standing C, but did not affect the partitioning of C among plant biomass pools. Spatial variation in net primary productivity and its [CO(2)]-induced enhancement was controlled primarily by N availability, with the difference between precipitation and potential evapotranspiration explaining most interannual variability. Consequently, [CO(2)]-induced net primary productivity enhancement ranged from 22 to 30% in different plots and years. *Through quantifying the effects of nutrient and water availability on the forest productivity response to elevated [CO(2)], we show that net primary productivity enhancement by elevated [CO(2)] is not uniform, but rather highly dependent on the availability of other growth resources.

Stress-induced beta-lactam antibiotic resistance mutation and sequences of stationary-phase mutations in the Escherichia coli chromosome.

In some enterobacterial pathogens, but not in Escherichia coli, loss-of-function mutations are a common route to clinically relevant beta-lactam antibiotic resistance. We previously constructed an assay system for studying enterobacterial beta-lactam resistance mutations using the well-developed genetics of E. coli by integrating enterobacterial ampRC genes into the E. coli chromosome. Like the cells of other enterobacteria, E. coli cells acquire beta-lactam resistance by ampD mutation. Here we show that starvation and stress responses provoke ampD beta-lactam resistance mutagenesis. When starved on lactose medium, Lac(-) strains used in mutagenesis studies accumulate ampD beta-lactam resistance mutations independent of Lac reversion. DNA double-strand break repair (DSBR) proteins and the SOS and RpoS stress responses are required for this mutagenesis, in agreement with the results obtained for lac reversion in these cells. Surprisingly, the stress-induced ampD mutations require DinB (DNA polymerase IV) and partially require error-prone DNA polymerase V, unlike lac mutagenesis, which requires only DinB. This assay demonstrates that real-world stressors, such as starvation, can induce clinically relevant resistance mutations. Finally, we used the ampD system to observe the true forward-mutation sequence spectrum of DSBR-associated stress-induced mutagenesis, for which previously only frameshift reversions were studied. We found that base substitutions outnumber frameshift mutations, as seen in other experimental systems showing stress-induced mutagenesis. The important evolutionary implication is that not only loss-of-function mutations but also change-of-function mutations can be generated by this mechanism.

Role of transitory carbon reserves during adjustment to climate variability and source-sink imbalances in oil palm (Elaeis guineensis).

Oil palm (Elaeis guineensis Jacq.) is a perennial, tropical, monocotyledonous plant characterized by simple architecture and low phenotypic plasticity, but marked by long development cycles of individual phytomers (a pair of one leaf and one inflorescence at its axil). Environmental effects on vegetative or reproductive sinks occur with various time lags depending on the process affected, causing source-sink imbalances. This study investigated how the two instantaneous sources of carbon assimilates, CO(2) assimilation and mobilization of transitory non-structural carbohydrate (NSC) reserves, may buffer such imbalances. An experiment was conducted in Indonesia during a 22-month period (from July 2006 to May 2008) at two contrasting locations (Kandista and Batu Mulia) using two treatments (control and complete fruit pruning treatment) in Kandista. Measurements included leaf gas exchange, dynamics of NSC reserves and dynamics of structural aboveground vegetative growth (SVG) and reproductive growth. Drought was estimated from a simulated fraction of transpirable soil water. The main sources of variation in source-sink relationships were (i) short-term reductions in light-saturated leaf CO(2) assimilation rate (A(max)) during seasonal drought periods, particularly in Batu Mulia; (ii) rapid responses of SVG rate to drought; and (iii) marked lag periods between 16 and 29 months of environmental effects on the development of reproductive sinks. The resulting source-sink imbalances were buffered by fluctuations in NSC reserves in the stem, which mainly consisted of glucose and starch. Starch was the main buffer for sink variations, whereas glucose dynamics remained unexplained. Even under strong sink limitation, no negative feedback on A(max) was observed. In conclusion, the different lag periods for environmental effects on assimilate sources and sinks in oil palm are mainly buffered by NSC accumulation in the stem, which can attain 50% (dw:dw) in stem tops. The resulting dynamics of growth and production are complex because several dozen phytomers of different phenological ages develop at any given time and interact with a common pool of reserves.

Fog interception by Sequoia sempervirens (D. Don) crowns decouples physiology from soil water deficit.

Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indicated that fog interception increased leaf water potential above that of leaves sheltered from fog. Furthermore, observed increases in leaf water potential exceeded the maximum water potential predicted if soil water was the only available water source. Because field observations were limited to two mature trees, we conducted a greenhouse experiment to investigate how fog interception influences plant water status and photosynthesis. Pre-dawn and midday branchlet water potential, leaf gas exchange and chlorophyll fluorescence were measured on S. sempervirens saplings exposed to increasing soil water deficit, with and without overnight canopy fog interception. Sapling fog interception increased leaf water potential and photosynthesis above the control and soil water deficit treatments despite similar dark-acclimated leaf chlorophyll fluorescence. The field observations and greenhouse experiment show that fog interception represents an overlooked flux into the soil-plant-atmosphere continuum that temporarily, but significantly, decouples leaf-level water and carbon relations from soil water availability.

Staphylococcus aureus ClpC ATPase is a late growth phase effector of metabolism and persistence.

Staphylococcus aureus Clp ATPases (molecular chaperones) alter normal physiological functions including an aconitase-mediated effect on post-stationary growth, acetate catabolism, and entry into death phase (Chatterjee et al., J. Bacteriol. 2005, 187, 4488-4496). In the present study, the global function of ClpC in physiology, metabolism, and late-stationary phase survival was examined using DNA microarrays and 2-D PAGE followed by MALDI-TOF MS. The results suggest that ClpC is involved in regulating the expression of genes and/or proteins of gluconeogenesis, the pentose-phosphate pathway, pyruvate metabolism, the electron transport chain, nucleotide metabolism, oxidative stress, metal ion homeostasis, stringent response, and programmed cell death. Thus, one major function of ClpC is balancing late growth phase carbon metabolism. Furthermore, these changes in carbon metabolism result in alterations of the intracellular concentration of free NADH, the amount of cell-associated iron, and fatty acid metabolism. This study provides strong evidence for ClpC as a critical factor in staphylococcal energy metabolism, stress regulation, and late-stationary phase survival; therefore, these data provide important insight into the adaptation of S. aureus toward a persister state in chronic infections.