Evaluating tidal marsh sustainability in the face of sea-level rise: a hybrid modeling approach applied to San Francisco Bay

Background

Tidal marshes will be threatened by increasing rates of sea-level rise (SLR) over the next century. Managers seek guidance on whether existing and restored marshes will be resilient under a range of potential future conditions, and on prioritizing marsh restoration and conservation activities.

Methodology

Building upon established models, we developed a hybrid approach that involves a mechanistic treatment of marsh accretion dynamics and incorporates spatial variation at a scale relevant for conservation and restoration decision-making. We applied this model to San Francisco Bay, using best-available elevation data and estimates of sediment supply and organic matter accumulation developed for 15 Bay subregions. Accretion models were run over 100 years for 70 combinations of starting elevation, mineral sediment, organic matter, and SLR assumptions. Results were applied spatially to evaluate eight Bay-wide climate change scenarios.

Principal Findings

Model results indicated that under a high rate of SLR (1.65 m/century), short-term restoration of diked subtidal baylands to mid marsh elevations (−0.2 m MHHW) could be achieved over the next century with sediment concentrations greater than 200 mg/L. However, suspended sediment concentrations greater than 300 mg/L would be required for 100-year mid marsh sustainability (i.e., no elevation loss). Organic matter accumulation had minimal impacts on this threshold. Bay-wide projections of marsh habitat area varied substantially, depending primarily on SLR and sediment assumptions. Across all scenarios, however, the model projected a shift in the mix of intertidal habitats, with a loss of high marsh and gains in low marsh and mudflats.

Conclusions/Significance

Results suggest a bleak prognosis for long-term natural tidal marsh sustainability under a high-SLR scenario. To minimize marsh loss, we recommend conserving adjacent uplands for marsh migration, redistributing dredged sediment to raise elevations, and concentrating restoration efforts in sediment-rich areas. To assist land managers, we developed a web-based decision support tool (www.prbo.org/sfbayslr).     

Phosphorus chemistry and bacterial community composition interact in brackish sediments receiving agricultural discharges

Background

External nutrient discharges have caused eutrophication in many estuaries and coastal seas such as the Baltic Sea. The sedimented nutrients can affect bacterial communities which, in turn, are widely believed to contribute to release of nutrients such as phosphorus from the sediment.

Methods

We investigated relationships between bacterial communities and chemical forms of phosphorus as well as elements involved in its cycling in brackish sediments using up-to-date multivariate statistical methods. Bacterial community composition was determined by terminal restriction fragment length polymorphism and cloning of the 16S rRNA gene.

Results and Conclusions

The bacterial community composition differed along gradients of nutrients, especially of different phosphorus forms, from the estuary receiving agricultural phosphorus loading to the open sea. This suggests that the chemical composition of sediment phosphorus, which has been affected by riverine phosphorus loading, influenced on bacterial communities. Chemical and spatial parameters explained 25% and 11% of the variation in bacterial communities. Deltaproteobacteria, presumptively sulphate and sulphur/iron reducing, were strongly associated to chemical parameters, also when spatial autocorrelation was taken into account. Sulphate reducers correlated positively with labile organic phosphorus and total nitrogen in the open sea sediments. Sulphur/iron reducers and sulphate reducers linked to iron reduction correlated positively with aluminium- and iron-bound phosphorus, and total iron in the estuary. The sulphate and sulphur/iron reducing bacteria can thus have an important role both in the mineralization and mobilization of nutrients from sediment.

Significance

Novelty in our study is that relationships between bacterial community composition and different phosphorus forms, instead of total phosphorus, were investigated. Total phosphorus does not necessarily bring out interactions between bacteria and phosphorus chemistry since proportions of easily usable mobile (reactive) phosphorus and immobile phosphorus forms in different sediments can vary. Our study suggested possible feedbacks between different forms of phosphorus and bacterial community composition.     

The Influence of Organic Material and Temperature on the Burial Tolerance of the Blue Mussel,Mytilus edulis: Considerations for the Management of Marine Aggregate Dredging

Rationale and Experimental Approach

Aggregate dredging is a growing source of anthropogenic disturbance in coastal UK waters and has the potential to impact marine systems through the smothering of benthic fauna with organically loaded screening discards. This study investigates the tolerance of the blue mussel, Mytilus edulis to such episodic smothering events using a multi-factorial design, including organic matter concentration, temperature, sediment fraction size and duration of burial as important predictor variables.

Results and Discussion

Mussel mortality was significantly higher in organically loaded burials when compared to control sediments after just 2 days. Particularly, M. edulis specimens under burial in fine sediment with high (1%) concentrations of organic matter experienced a significantly higher mortality rate (p<0.01) than those under coarse control aggregates. Additionally, mussels exposed to the summer maximum temperature treatment (20°C) exhibited significantly increased mortality (p<0.01) compared to those in the ambient treatment group (15°C). Total Oxygen Uptake rates of experimental aggregates were greatest (112.7 mmol m^-2 day^-1) with 1% organic loadings in coarse sediment at 20°C. Elevated oxygen flux rates in porous coarse sediments are likely to be a function of increased vertical migration of anaerobically liberated sulphides to the sediment-water interface. However, survival of M. edulis under bacterial mats of Beggiatoa spp. indicates the species’ resilience to sulphides and so we propose that the presence of reactive organic matter within the burial medium may facilitate bacterial growth and increase mortality through pathogenic infection. This may be exacerbated under the stable interstitial conditions in fine sediment and increased bacterial metabolism under high temperatures. Furthermore, increased temperature may impose metabolic demands upon the mussel that cannot be met during burial-induced anaerobiosis.

Summary

Lack of consideration for the role of organic matter and temperature during sedimentation events may lead to an overestimation of the tolerance of benthic species to smothering from dredged material.     

Mutualistic ants contribute to tank-bromeliad nutrition

Background and Aims

Epiphytism imposes physiological constraints resulting from the lack of access to the nutrient sources available to ground-rooted plants. A conspicuous adaptation in response to that lack is the phytotelm (plant-held waters) of tank-bromeliad species that are often nutrient-rich. Associations with terrestrial invertebrates also result in higher plant nutrient acquisition. Assuming that tank-bromeliads rely on reservoir-assisted nutrition, it was hypothesized that the dual association with mutualistic ants and the phytotelm food web provides greater nutritional benefits to the plant compared with those bromeliads involved in only one of these two associations.

Methods

Quantitative (water volume, amount of fine particulate organic matter, predator/prey ratio, algal density) and qualitative variables (ant-association and photosynthetic pathways) were compared for eight tank- and one tankless-bromeliad morphospecies from French Guiana. An analysis was also made of which of these variables affect nitrogen acquisition (leaf N and δ¹⁵N).

Key Results

All variables were significantly different between tank-bromeliad species. Leaf N concentrations and leaf δ¹⁵N were both positively correlated with the presence of mutualistic ants. The amount of fine particulate organic matter and predator/prey ratio had a positive and negative effect on leaf δ¹⁵N, respectively. Water volume was positively correlated with leaf N concentration whereas algal density was negatively correlated. Finally, the photosynthetic pathway (C₃ vs. CAM) was positively correlated with leaf N concentration with a slightly higher N concentration for C₃-Tillandsioideae compared with CAM-Bromelioideae.

Conclusions

The study suggests that some of the differences in N nutrition between bromeliad species can be explained by the presence of mutualistic ants. From a nutritional standpoint, it is more advantageous for a bromeliad to use myrmecotrophy via its roots than to use carnivory via its tank. The results highlight a gap in our knowledge of the reciprocal interactions between bromeliads and the various trophic levels (from bacteria to large metazoan predators) that intervene in reservoir-assisted nutrition.     

Mobility, expansion and management of a multi-species scuba diving fishery in East Africa

Background

Scuba diving fishing, predominantly targeting sea cucumbers, has been documented to occur in an uncontrolled manner in the Western Indian Ocean and in other tropical regions. Although this type of fishing generally indicates a destructive activity, little attention has been directed towards this category of fishery, a major knowledge gap and barrier to management.

Methodology and Principal Findings

With the aim to capture geographic scales, fishing processes and social aspects the scuba diving fishery that operate out of Zanzibar was studied using interviews, discussions, participant observations and catch monitoring. The diving fishery was resilient to resource declines and had expanded to new species, new depths and new fishing grounds, sometimes operating approximately 250 km away from Zanzibar at depths down to 50 meters, as a result of depleted easy-access stock. The diving operations were embedded in a regional and global trade network, and its actors operated in a roving manner on multiple spatial levels, taking advantage of unfair patron-client relationships and of the insufficient management in Zanzibar.

Conclusions and Significance

This study illustrates that roving dynamics in fisheries, which have been predominantly addressed on a global scale, also take place at a considerably smaller spatial scale. Importantly, while proposed management of the sea cucumber fishery is often generic to a simplified fishery situation, this study illustrates a multifaceted fishery with diverse management requirements. The documented spatial scales and processes in the scuba diving fishery emphasize the need for increased regional governance partnerships to implement management that fit the spatial scales and processes of the operation.     

Ecosystem services transcend boundaries: estuaries provide resource subsidies and influence functional diversity in coastal benthic communities

Background

Estuaries are highly productive ecosystems that can export organic matter to coastal seas (the ‘outwelling hypothesis’). However the role of this food resource subsidy on coastal ecosystem functioning has not been examined.

Methodology/Principal Findings

We investigated the influence of estuarine primary production as a resource subsidy and the influence of estuaries on biodiversity and ecosystem functioning in coastal mollusk-dominated sediment communities. Stable isotope values (δ¹³C, δ¹⁵N) demonstrated that estuarine primary production was exported to the adjacent coast and contributed to secondary production up to 4 km from the estuary mouth. Further, isotope signatures of suspension feeding bivalves on the adjacent coast (Dosinia subrosea) closely mirrored the isotope values of the dominant bivalves inside the estuaries (Austrovenus stutchburyi), indicating utilization of similar organic matter sources. However, the food subsidies varied between estuaries; with estuarine suspended particulate organic matter (SPOM) dominant at Tairua estuary, while seagrass and fringing vegetation detritus was proportionately more important at Whangapoua estuary, with lesser contributions of estuarine SPOM. Distance from the estuary mouth and the size and density of large bivalves (Dosinia spp.) had a significant influence on the composition of biological traits in the coastal macrobenthic communities, signaling the potential influence of these spatial subsidies on ecosystem functioning.

Conclusions/Significance

Our study demonstrated that the locations where ecosystem services like productivity are generated are not necessarily where the services are utilized. Further, we identified indirect positive effects of the nutrient subsidies on biodiversity (the estuarine subsidies influenced the bivalves, which in turn affected the diversity and functional trait composition of the coastal sediment macrofaunal communities). These findings highlight the importance of integrative ecosystem-based management that maintains the connectivity of estuarine and coastal ecosystems.     

Hemolytic and cytotoxic properties of saponin purified from Holothuria leucospilota sea cucumber

Background:

Holothuroids (sea cucumbers) are members of the phylum echinodermata, which produce saponins. Saponins exhibit a wide spectrum of pharmacological and biological activities. In this study, we isolated the crude saponins from the body wall of the dominant Iranian species of sea cucumber, Holothuria leucospilota (H. leucospilota). The purpose of this study was to confirm the presence of saponins in the Persian Gulf H. leucospilota and study the hemolytic and cytotoxic activities of these compounds.

Methods:

The body wall of sea cucumber was dried and powdered and the crude saponins were isolated using various solvents. The crude saponins were further purified by column chromatography using HP-20 resin. The foam test, Thin Layer Chromatography (TLC), hemolytic assay, and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of saponins. Cytotoxicity was analyzed using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay on A549 cells, a human lung cancer cell line.

Results:

The foam test, hemolytic assay, and TLC supported the presence of saponin compounds in the 80% ethanol fraction of H. leucospilota. The infrared (IR) spectrum of the extract showed hydroxyl (-OH), alkyl (C-H), ether (C-O) and ester (–C=O) absorption characteristic of teriterpenoid saponins. The C-O-C absorption indicated glycoside linkages to the sapogenins. The crude saponin extracted from sea cucumber was cytotoxic to A549 cells.

Conclusion:

The 80% ethanol fraction of saponin isolated from H. leucospilota exhibited hemolytic activity and offers promise as an anti-cancer candidate.Key Words: Sea cucumber, Holothuria leucospilota, Saponin, Hemolytic assay, Cytotoxicity assay     

Cholesterol Pathways Affected by Small Molecules That Decrease Sterol Levels in Niemann-Pick Type C Mutant Cells

Background

Niemann-Pick type C (NPC) disease is a genetically inherited multi-lipid storage disorder with impaired efflux of cholesterol from lysosomal storage organelles.

Methodology/Principal Findings

The effect of screen-selected cholesterol lowering compounds on the major sterol pathways was studied in CT60 mutant CHO cells lacking NPC1 protein. Each of the selected chemicals decreases cholesterol in the lysosomal storage organelles of NPC1 mutant cells through one or more of the following mechanisms: increased cholesterol efflux from the cell, decreased uptake of low-density lipoproteins, and/or increased levels of cholesteryl esters. Several chemicals promote efflux of cholesterol to extracellular acceptors in both non-NPC and NPC1 mutant cells. The uptake of low-density lipoprotein-derived cholesterol is inhibited by some of the studied compounds.

Conclusions/Significance

Results herein provide the information for prioritized further studies in identifying molecular targets of the chemicals. This approach proved successful in the identification of seven chemicals as novel inhibitors of lysosomal acid lipase (Rosenbaum et al, Biochim. Biophys. Acta. 2009, 1791:1155–1165).     

The barley MATE gene,HvAACT1, increases citrate efflux and Al3+ tolerance when expressed in wheat and barley

Background and Aims

Aluminium is toxic in acid soils because the soluble Al³⁺ inhibits root growth. A mechanism of Al³⁺ tolerance discovered in many plant species involves the release of organic anions from root apices. The Al³⁺-activated release of citrate from the root apices of Al³⁺-tolerant genotypes of barley is controlled by a MATE gene named HvAACT1 that encodes a citrate transport protein located on the plasma membrane. The aim of this study was to investigate whether expressing HvAACT1 with a constitutive promoter in barley and wheat can increase citrate efflux and Al³⁺ tolerance of these important cereal species.

Methods HvAACT1

was over-expressed in wheat (Triticum aestivum) and barley (Hordeum vulgare) using the maize ubiquitin promoter. Root apices of transgenic and control lines were analysed for HvAACT1 expression and organic acid efflux. The Al³⁺ tolerance of transgenic and control lines was assessed in both hydroponic solution and acid soil.

Key Results and Conclusions

Increased HvAACT1 expression in both cereal species was associated with increased citrate efflux from root apices and enhanced Al³⁺ tolerance, thus demonstrating that biotechnology can complement traditional breeding practices to increase the Al³⁺ tolerance of important crop plants.     

Retained duplicate genes in green alga Chlamydomonas reinhardtii tend to be stress responsive and experience frequent response gains

Background

Green algae belong to a group of photosynthetic organisms that occupy diverse habitats, are closely related to land plants, and have been studied as sources of food and biofuel. Although multiple green algal genomes are available, a global comparative study of algal gene families has not been carried out. To investigate how gene families and gene expression have evolved, particularly in the context of stress response that have been shown to correlate with gene family expansion in multiple eukaryotes, we characterized the expansion patterns of gene families in nine green algal species, and examined evolution of stress response among gene duplicates in Chlamydomonas reinhardtii.

Results

Substantial variation in domain family sizes exists among green algal species. Lineage-specific expansion of families occurred throughout the green algal lineage but inferred gene losses occurred more often than gene gains, suggesting a continuous reduction of algal gene repertoire. Retained duplicates tend to be involved in stress response, similar to land plant species. However, stress responsive genes tend to be pseudogenized as well. When comparing ancestral and extant gene stress response state, we found that response gains occur in 13% of duplicate gene branches, much higher than 6% in Arabidopsis thaliana.

Conclusion

The frequent gains of stress response among green algal duplicates potentially reflect a high rate of innovation, resulting in a species-specific gene repertoire that contributed to adaptive response to stress. This could be further explored towards deciphering the mechanism of stress response, and identifying suitable green algal species for oil production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1335-5) contains supplementary material, which is available to authorized users.     

Oxidative stress induces distinct physiological responses in the two Trebouxia phycobionts of the lichen Ramalina farinacea

Background and Aims

Most lichens form associations with Trebouxia phycobionts and some of them simultaneously include genetically different algal lineages. In other symbiotic systems involving algae (e.g. reef corals), the relative abundances of different endosymbiotic algal clades may change over time. This process seems to provide a mechanism allowing the organism to respond to environmental stress. A similar mechanism may operate in lichens with more than one algal lineage, likewise protecting them against environmental stresses. Here, the physiological responses to oxidative stress of two distinct Trebouxia phycobionts (provisionally named TR1 and TR9) that coexist within the lichen Ramalina farinacea were analysed.

Methods

Isolated phycobionts were exposed to oxidative stress through the reactive oxygen species propagator cumene hydroperoxide (CuHP). Photosynthetic pigments and proteins, photosynthesis (through modulated chlorophyll fluorescence), the antioxidant enzymes superoxide dismutase (SOD) and glutathione reductase (GR), and the stress-related protein HSP70 were analysed.

Key Results

Photosynthetic performance was severely impaired by CuHP in phycobionts, as indicated by decreases in the maximal PSII photochemical efficiency (F_v/F_m), the quantum efficiency of PSII (Φ_PSII) and the non-photochemical dissipation of energy (NPQ). However, the CuHP-dependent decay in photosynthesis was significantly more severe in TR1, which also showed a lower NPQ and a reduced ability to preserve chlorophyll a, carotenoids and D1 protein. Additionally, differences were observed in the capacities of the two phycobionts to modulate antioxidant activities and HPS70 levels when exposed to oxidative stress. In TR1, CuHP significantly diminished HSP70 and GR but did not change SOD activities. In contrast, in TR9 the levels of both antioxidant enzymes and those of HSP70 increased in response to CuHP.

Conclusions

The better physiological performance of TR9 under oxidative conditions may reflect its greater capacity to undertake key metabolic adjustments, including increased non-photochemical quenching, higher antioxidant protection and the induction of repair mechanisms.     

Genomes of Alteromonas australica,a world apart

Background

Alteromonas is a genus of marine bacteria that is very easy to isolate and grow in the laboratory. There are genomes available of the species Alteromonas macleodii from different locations around the world and an Alteromonas sp. isolated from a sediment in Korea. We have analyzed the genomes of two strains classified by 16S rRNA (>99% similarity) as the recently described species Alteromonas australica, and isolated from opposite ends of the world; A. australica DE170 was isolated in the South Adriatic (Mediterranean) at 1000 m depth while A. australica H17^T was isolated from a sea water sample collected in St Kilda Beach, Tasman Sea.

Results

Although these two strains belong to a clearly different species from A. macleodii, the overall synteny is well preserved and the flexible genomic islands seem to code for equivalent functions and be located at similar positions. Actually the genomes of all the Alteromonas species known to date seem to preserve synteny quite well with the only exception of the sediment isolate SN2. Among the specific metabolic features found for the A. australica isolates there is the degradation of xylan and production of cellulose as extracellular polymeric substance by DE170 or the potential ethanol/methanol degradation by H17^T.

Conclusions

The genomes of the two A. australica isolates are not more different than those of strains of A. macleodii isolated from the same sample. Actually the recruitment from metagenomes indicates that all the available genomes are found in most tropical-temperate marine samples analyzed and that they live in consortia of several species and multiple clones within each. Overall the hydrolytic activities of the Alteromonas genus as a whole are impressive and fit with its known capabilities to exploit sudden inputs of organic matter in their environment.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-483) contains supplementary material, which is available to authorized users.     

CO2 efflux from cleared mangrove peat

Background

CO₂ emissions from cleared mangrove areas may be substantial, increasing the costs of continued losses of these ecosystems, particularly in mangroves that have highly organic soils.

Methodology/Principal Findings

We measured CO₂ efflux from mangrove soils that had been cleared for up to 20 years on the islands of Twin Cays, Belize. We also disturbed these cleared peat soils to assess what disturbance of soils after clearing may have on CO₂ efflux. CO₂ efflux from soils declines from time of clearing from ∼10 600 tonnes km⁻² year⁻¹ in the first year to 3000 tonnes km² year⁻¹ after 20 years since clearing. Disturbing peat leads to short term increases in CO₂ efflux (27 umol m⁻² s⁻¹), but this had returned to baseline levels within 2 days.

Conclusions/Significance

Deforesting mangroves that grow on peat soils results in CO₂ emissions that are comparable to rates estimated for peat collapse in other tropical ecosystems. Preventing deforestation presents an opportunity for countries to benefit from carbon payments for preservation of threatened carbon stocks.     

White matter and cognition in adults who were born preterm

Background and Purpose

Individuals born very preterm (before 33 weeks of gestation, VPT) are at risk of damage to developing white matter, which may affect later cognition and behaviour.

Methods

We used diffusion tensor MRI (DT-MRI) to assess white matter microstructure (fractional anisotropy; FA) in 80 VPT and 41 term-born individuals (mean age 19.1 years, range 17–22, and 18.5 years, range17–22 years, respectively). VPT individuals were part of a 1982–1984 birth cohort which had been followed up since birth; term individuals were recruited by local press advertisement. General intellectual function, executive function and memory were assessed.

Results

The VPT group had reduced FA in four clusters, and increased FA in four clusters relative to the Term group, involving several association tracts of both hemispheres. Clusters of increased FA were associated with more severe neonatal brain injury in the VPT group. Clusters of reduced FA were associated with lower birth weight and perinatal hypoxia, and with reduced adult cognitive performance in the VPT group only.

Conclusions

Alterations of white matter microstructure persist into adulthood in VPT individuals and are associated with cognitive function.     

Incidental Findings on Brain MR Imaging in Older Community-Dwelling Subjects Are Common but Serious Medical Consequences Are Rare: A Cohort Study

Objectives

Incidental findings in neuroimaging occur in 3% of volunteers. Most data come from young subjects. Data on their occurrence in older subjects and their medical, lifestyle and financial consequences are lacking. We determined the prevalence and medical consequences of incidental findings found in community-dwelling older subjects on brain magnetic resonance imaging.

Design

Prospective cohort observational study.

Setting

Single centre study with input from secondary care.

Participants

Lothian Birth Cohort 1936, a study of cognitive ageing.

Main Outcome Measures

Incidental findings identified by two consultant neuroradiologists on structural brain magnetic resonance imaging at age 73 years; resulting medical referrals and interventions.

Primary and Secondary Outcome Measures

Prevalence of incidental findings by individual categories: neoplasms, cysts, vascular lesions, developmental, ear, nose or throat anomalies, by intra- and extracranial location; visual rating of white matter hyperintensities and brain atrophy.

Results

There were 281 incidental findings in 223 (32%) of 700 subjects, including 14 intra- or extracranial neoplasms (2%), 15 intracranial vascular anomalies (2%), and 137 infarcts or haemorrhages (20%). Additionally, 153 had moderate/severe deep white matter hyperintensities (22%) and 176 had cerebral atrophy at, or above, the upper limit of normal (25%) compared with a normative population template. The incidental findings were unrelated to white matter hyperintensities or atrophy; about a third of subjects had both incidental findings and moderate or severe WMH and a quarter had incidental findings and atrophy. The incidental findings resulted in one urgent and nine non-urgent referrals for further medical assessment, but ultimately in no new treatments.

Conclusions

In community-dwelling older subjects, incidental findings, including white matter hyperintensities and atrophy, were common. However, many findings were not of medical importance and, in this age group, most did not result in further assessment and none in change of treatment.     

The progressive ankylosis gene product ANK regulates extracellular ATP levels in primary articular chondrocytes

Introduction

Extracellular ATP (eATP) is released by articular chondrocytes under physiological and pathological conditions. High eATP levels cause pathologic calcification, damage cartilage, and mediate pain. We recently showed that stable over-expression of the progressive ankylosis gene product, ANK, increased chondrocyte eATP levels, but the mechanisms of this effect remained unexplored. The purpose of this work was to further investigate mechanisms of eATP efflux in primary articular chondrocytes and to better define the role of ANK in this process.

Methods

We measured eATP levels using a bioluminescence-based assay in adult porcine articular chondrocyte media with or without a 10 minute exposure to hypotonic stress. siRNAs for known ATP membrane transporters and pharmacologic inhibitors of ATP egress pathways were used to identify participants involved in chondrocyte eATP release.

Results

eATP levels increased after exposure to hypotonic media in a calcium-dependent manner in monolayer and 3-dimensional agarose gel cultures (p < 0.001). A potent transient receptor potential vanilloid 4 (TRPV4) agonist mimicked the effects of hypotonic media. ANK siRNA suppressed basal (p < 0.01) and hypotonically-stressed (p < 0.001) ATP levels. This effect was not mediated by altered extracellular pyrophosphate (ePPi) levels, and was mimicked by the ANK inhibitor, probenecid (p < 0.001). The P2X7/4 receptor inhibitor Brilliant Blue G also suppressed eATP efflux induced by hypotonic media (p < 0.001), while ivermectin, a P2X4 receptor stimulant, increased eATP levels (p < 0.001). Pharmacologic inhibitors of hemichannels, maxianion channels and other volume-sensitive eATP efflux pathways did not suppress eATP levels.

Conclusions

These findings implicate ANK and P2X7/4 receptors in chondrocyte eATP efflux. Understanding the mechanisms of eATP efflux may result in novel therapies for calcium crystal arthritis and osteoarthritis.     

Cyanolichens can have both cyanobacteria and green algae in a common layer as major contributors to photosynthesis

Background and Aims

Cyanolichens are usually stated to be bipartite (mycobiont plus cyanobacterial photobiont). Analyses revealed green algal carbohydrates in supposedly cyanobacterial lichens (in the genera Pseudocyphellaria, Sticta and Peltigera). Investigations were carried out to determine if both cyanobacteria and green algae were present in these lichens and, if so, what were their roles.

Methods

The types of photobiont present were determined by light and fluorescence microscopy. Small carbohydrates were analysed to detect the presence of green algal metabolites. Thalli were treated with selected strengths of Zn²⁺ solutions that stop cyanobacterial but not green algal photosynthesis. CO₂ exchange was measured before and after treatment to determine the contribution of each photobiont to total thallus photosynthesis. Heterocyst frequencies were determined to clarify whether the cyanobacteria were modified for increased nitrogen fixation (high heterocyst frequencies) or were normal, vegetative cells.

Key Results

Several cyanobacterial lichens had green algae present in the photosynthetic layer of the thallus. The presence of the green algal transfer carbohydrate (ribitol) and the incomplete inhibition of thallus photosynthesis upon treatment with Zn²⁺ solutions showed that both photobionts contributed to the photosynthesis of the lichen thallus. Low heterocyst frequencies showed that, despite the presence of adjacent green algae, the cyanobacteria were not altered to increase nitrogen fixation.

Conclusions

These cyanobacterial lichens are a tripartite lichen symbiont combination in which the mycobiont has two primarily photosynthetic photobionts, ‘co-primary photobionts’, a cyanobacterium (dominant) and a green alga. This demonstrates high flexibility in photobiont choice by the mycobiont in the Peltigerales. Overall thallus appearance does not change whether one or two photobionts are present in the cyanobacterial thallus. This suggests that, if there is a photobiont effect on thallus structure, it is not specific to one or the other photobiont.     

Metagenomics reveals that detoxification systems are underrepresented in marine bacterial communities

Background

Environmental shotgun sequencing (metagenomics) provides a new way to study communities in microbial ecology. We here use sequence data from the Global Ocean Sampling (GOS) expedition to investigate toxicant selection pressures revealed by the presence of detoxification genes in marine bacteria. To capture a broad range of potential toxicants we selected detoxification protein families representing systems protecting microorganisms from a variety of stressors, such as metals, organic compounds, antibiotics and oxygen radicals.

Results

Using a bioinformatics procedure based on comparative analysis to finished bacterial genomes we found that the amount of detoxification genes present in marine microorganisms seems surprisingly small. The underrepresentation is particularly evident for toxicant transporters and proteins involved in detoxifying metals. Exceptions are enzymes involved in oxidative stress defense where peroxidase enzymes are more abundant in marine bacteria compared to bacteria in general. In contrast, catalases are almost completely absent from the open ocean environment, suggesting that peroxidases and peroxiredoxins constitute a core line of defense against reactive oxygen species (ROS) in the marine milieu.

Conclusions

We found no indication that detoxification systems would be generally more abundant close to the coast compared to the open ocean. On the contrary, for several of the protein families that displayed a significant geographical distribution, like peroxidase, penicillin binding transpeptidase and divalent ion transport protein, the open ocean samples showed the highest abundance. Along the same lines, the abundance of most detoxification proteins did not increase with estimated pollution. The low level of detoxification systems in marine bacteria indicate that the majority of marine bacteria have a low capacity to adapt to increased pollution. Our study exemplifies the use of metagenomics data in ecotoxicology, and in particular how anthropogenic consequences on life in the sea can be examined.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-749) contains supplementary material, which is available to authorized users.     

11C-Acetate PET Imaging in Patients with Multiple Sclerosis

Background

Activation of glial cells is a cardinal feature in multiple sclerosis (MS) pathology, and acetate has been reported to be selectively uptaken by astrocytes in the CNS. The aim of this study was to investigate the efficacy of PET with ¹¹C-acetate for MS diagnosis.

Materials and Methods

Six patients with relapsing-remitting MS and 6 healthy volunteers (HV) were enrolled. The ¹¹C-acetate brain uptake on PET was measured in patients with MS and HV. Volume-of-interest analysis of cerebral gray and white matter based on the segmentation technique for co-registered MRI and voxel-based statistical parametric analysis were performed. Correlation between ¹¹C-acetate uptake and the lesion number in T1- and T2- weighted MR images were also assessed.

Results

The standardized uptake value (SUV) of ¹¹C-acetate was increased in both white and gray matter in MS patients compared to HV. Voxel-based statistical analysis revealed a significantly increased SUV relative to that in the bilateral thalami (SUVt) in a broad area of white matter, particularly in the subcortical white matter of MS patients. The numbers of T2 lesions and T1 black holes were significantly correlated with SUV of ¹¹C-acetate in white and gray matter.

Conclusions

The ¹¹C-acetate uptake significantly increased in MS patients and correlated to the number of MRI lesions. These preliminary data suggest that ¹¹C-acetate PET can be a useful clinical examination for MS patients.