Dual thermal ecotypes coexist within a nearly genetically identical population of the unicellular marine cyanobacterium Synechococcus.

The extent and ecological significance of intraspecific functional diversity within marine microbial populations is still poorly understood, and it remains unclear if such strain-level microdiversity will affect fitness and persistence in a rapidly changing ocean environment. In this study, we cultured 11 sympatric strains of the ubiquitous marine picocyanobacterium Synechococcus isolated from a Narragansett Bay (RI) phytoplankton community thermal selection experiment. Thermal performance curves revealed selection at cool and warm temperatures had subdivided the initial population into thermotypes with pronounced differences in maximum growth temperatures. Curiously, the genomes of all 11 isolates were almost identical (average nucleotide identities of >99.99%, with >99% of the genome aligning) and no differences in gene content or single nucleotide variants were associated with either cool or warm temperature phenotypes. Despite a very high level of genomic similarity, sequenced epigenomes for two strains showed differences in methylation on genes associated with photosynthesis. These corresponded to measured differences in photophysiology, suggesting a potential pathway for future mechanistic research into thermal microdiversity. Our study demonstrates that present-day marine microbial populations can harbor cryptic but environmentally relevant thermotypes which may increase their resilience to future rising temperatures.

Molecular underpinnings and biogeochemical consequences of enhanced diatom growth in a warming Southern Ocean.

The Southern Ocean (SO) harbors some of the most intense phytoplankton blooms on Earth. Changes in temperature and iron availability are expected to alter the intensity of SO phytoplankton blooms, but little is known about how these changes will influence community composition and downstream biogeochemical processes. We performed light-saturated experimental manipulations on surface ocean microbial communities from McMurdo Sound in the Ross Sea to examine the effects of increased iron availability (+2 nM) and warming (+3 and +6 °C) on nutrient uptake, as well as the growth and transcriptional responses of two dominant diatoms, Fragilariopsis and Pseudo-nitzschia We found that community nutrient uptake and primary productivity were elevated under both warming conditions without iron addition (relative to ambient -0.5 °C). This effect was greater than additive under concurrent iron addition and warming. Pseudo-nitzschia became more abundant under warming without added iron (especially at 6 °C), while Fragilariopsis only became more abundant under warming in the iron-added treatments. We attribute the apparent advantage Pseudo-nitzschia shows under warming to up-regulation of iron-conserving photosynthetic processes, utilization of iron-economic nitrogen assimilation mechanisms, and increased iron uptake and storage. These data identify important molecular and physiological differences between dominant diatom groups and add to the growing body of evidence for Pseudo-nitzschia's increasingly important role in warming SO ecosystems. This study also suggests that temperature-driven shifts in SO phytoplankton assemblages may increase utilization of the vast pool of excess nutrients in iron-limited SO surface waters and thereby influence global nutrient distribution and carbon cycling.

Natural ocean iron fertilization and climate variability over geological periods.

Marine primary producers are largely dependent on and shape the Earth's climate, although their relationship with climate varies over space and time. The growth of phytoplankton and associated marine primary productivity in most of the modern global ocean is limited by the supply of nutrients, including the micronutrient iron. The addition of iron via episodic and frequent events drives the biological carbon pump and promotes the sequestration of atmospheric carbon dioxide (CO2 ) into the ocean. However, the dependence between iron and marine primary producers adaptively changes over different geological periods due to the variation in global climate and environment. In this review, we examined the role and importance of iron in modulating marine primary production during some specific geological periods, that is, the Great Oxidation Event (GOE) during the Huronian glaciation, the Snowball Earth Event during the Cryogenian, the glacial-interglacial cycles during the Pleistocene, and the period from the last glacial maximum to the late Holocene. Only the change trend of iron bioavailability and climate in the glacial-interglacial cycles is consistent with the Iron Hypothesis. During the GOE and the Snowball Earth periods, although the bioavailability of iron in the ocean and the climate changed dramatically, the changing trend of many factors contradicted the Iron Hypothesis. By detangling the relationship among marine primary productivity, iron availability and oceanic environments in different geological periods, this review can offer some new insights for evaluating the impact of ocean iron fertilization on removing CO2 from the atmosphere and regulating the climate.

Defect Detection and Imaging in Composite Structures Using Magnetostrictive Patch Transducers.

The use of thin magnetostrictive patches to generate and detect guided waves within the composite samples is investigated for defect detection. This approach has been implemented using SH0 shear horizontal guided waves in both CFRP and GFRP plates. A magnetostrictive patch transducer was able to generate SH0 waves with known directional characteristics. The synthetic aperture focusing technique (SAFT) was then used to reconstruct images of defects using multiple transmission and detection locations. The results for imaging defects in both types of material are presented.

Why Environmental Biomarkers Work: Transcriptome-Proteome Correlations and Modeling of Multistressor Experiments in the Marine Bacterium Trichodesmium.

Ocean microbial communities are important contributors to the global biogeochemical reactions that sustain life on Earth. The factors controlling these communities are being increasingly explored using metatranscriptomic and metaproteomic environmental biomarkers. Using published proteomes and transcriptomes from the abundant colony-forming cyanobacterium Trichodesmium (strain IMS101) grown under varying Fe and/or P limitation in low and high CO2, we observed robust correlations of stress-induced proteins and RNAs (i.e., involved in transport and homeostasis) that yield useful information on the nutrient status under low and/or high CO2. Conversely, transcriptional and translational correlations of many other central metabolism pathways exhibit broad discordance. A cellular RNA and protein production/degradation model demonstrates how biomolecules with small initial inventories, such as environmentally responsive proteins, achieve large increases in fold-change units as opposed to those with a higher basal expression and inventory such as metabolic systems. Microbial cells, due to their immersion in the environment, tend to show large adaptive responses in both RNA and protein that result in transcript-protein correlations. These observations and model results demonstrate multi-omic coherence for environmental biomarkers and provide the underlying mechanism for those observations, supporting the promise for global application in detecting responses to environmental stimuli in a changing ocean.

Long-Term m5C Methylome Dynamics Parallel Phenotypic Adaptation in the Cyanobacterium Trichodesmium.

A major challenge in modern biology is understanding how the effects of short-term biological responses influence long-term evolutionary adaptation, defined as a genetically determined increase in fitness to novel environments. This is particularly important in globally important microbes experiencing rapid global change, due to their influence on food webs, biogeochemical cycles, and climate. Epigenetic modifications like methylation have been demonstrated to influence short-term plastic responses, which ultimately impact long-term adaptive responses to environmental change. However, there remains a paucity of empirical research examining long-term methylation dynamics during environmental adaptation in nonmodel, ecologically important microbes. Here, we show the first empirical evidence in a marine prokaryote for long-term m5C methylome modifications correlated with phenotypic adaptation to CO2, using a 7-year evolution experiment (1,000+ generations) with the biogeochemically important marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly changed in response to high (750 µatm) CO2 exposure and were maintained for at least 4.5 years of CO2 selection. After 7 years of CO2 selection, however, m5C methylation levels that initially responded to high-CO2 returned to ancestral, ambient CO2 levels. Concurrently, high-CO2 adapted growth and N2 fixation rates remained significantly higher than those of ambient CO2 adapted cell lines irrespective of CO2 concentration, a trend consistent with genetic assimilation theory. These data demonstrate the maintenance of CO2-responsive m5C methylation for 4.5 years alongside phenotypic adaptation before returning to ancestral methylation levels. These observations in a globally distributed marine prokaryote provide critical evolutionary insights into biogeochemically important traits under global change.

Integrating the impact of global change on the niche and physiology of marine nitrogen-fixing cyanobacteria.

Marine nitrogen fixation is a major source of new nitrogen to the ocean, which interacts with climate driven changes to physical nutrient supply to regulate the response of ocean primary production in the oligotrophic tropical ocean. Warming and changes in nutrient supply may alter the ecological niche of nitrogen-fixing organisms, or 'diazotrophs', however, impacts of warming on diazotroph physiology may also be important. Lab-based studies reveal that warming increases the nitrogen fixation-specific elemental use efficiency (EUE) of two prevalent marine diazotrophs, Crocosphaera and Trichodesmium, thus reducing their requirements for the limiting nutrients iron and phosphorus. Here, we coupled a new diazotroph model based upon observed diazotroph energetics of growth and resource limitation to a state-of-the-art global model of phytoplankton physiology and ocean biogeochemistry. Our model is able to address the integrated response of nitrogen fixation by Trichodesmium and Crocosphaera to warming under the IPCC high emission RCP8.5 scenario for the first time. Our results project a global decline in nitrogen fixation over the coming century. However, the regional response of nitrogen fixation to climate change is modulated by the diazotroph-specific thermal performance curves and EUE, particularly in the Pacific Ocean, which shapes global trends. Spatially, the response of both diazotrophs is similar with expansion towards higher latitudes and reduced rates of nitrogen fixation in the lower latitudes. Overall, 95%-97% of the nitrogen fixation climate signal can be attributed to the combined effect of temperature on the niche and physiology of marine diazotrophs, with decreases being associated with a reduced niche and increases resulting due to a combination of expanding niche and temperature driven changes to EUE. Climate change impacts on both the niche and physiology of marine diazotrophs interact to shape patterns of marine nitrogen fixation, which will have important implications for ocean productivity in the future.

Temperature variability interacts with mean temperature to influence the predictability of microbial phenotypes.

Despite their relatively high thermal optima (Topt ), tropical taxa may be particularly vulnerable to a rising baseline and increased temperature variation because they live in relatively stable temperatures closer to their Topt . We examined how microbial eukaryotes with differing thermal histories responded to temperature fluctuations of different amplitudes (0 control, ±2, ±4°C) around mean temperatures below or above their Topt . Cosmopolitan dinoflagellates were selected based on their distinct thermal traits and included two species of the same genus (tropical and temperate Coolia spp.), and two strains of the same species maintained at different temperatures for >500 generations (tropical Amphidinium massartii control temperature and high temperature, CT and HT, respectively). There was a universal decline in population growth rate under temperature fluctuations, but strains with narrower thermal niche breadth (temperate Coolia and HT) showed ~10% greater reduction in growth. At suboptimal mean temperatures, cells in the cool phase of the fluctuation stopped dividing, fixed less carbon (C) and had enlarged cell volumes that scaled positively with elemental C, N, and P and C:Chlorophyll-a. However, at a supra-optimal mean temperature, fixed C was directed away from cell division and novel trait combinations developed, leading to greater phenotypic diversity. At the molecular level, heat-shock proteins, and chaperones, in addition to transcripts involving genome rearrangements, were upregulated in CT and HT during the warm phase of the supra-optimal fluctuation (30 ± 4°C), a stress response indicating protection. In contrast, the tropical Coolia species upregulated major energy pathways in the warm phase of its supra-optimal fluctuation (25 ± 4°C), indicating a broadscale shift in metabolism. Our results demonstrate divergent effects between taxa and that temporal variability in environmental conditions interacts with changes in the thermal mean to mediate microbial responses to global change, with implications for biogeochemical cycling.

The Effect of Changes in Magnetic Field and Frequency on the Vibration of a Thin Magnetostrictive Patch as a Tool for Generating Guided Ultrasonic Waves.

A set of experiments was designed and conducted to investigate the vibrational ultrasonic response of a thin magnetostrictive patch bonded to a glass plate, with changes in static and dynamic magnetic fields applied to the patch. Such arrangements are often used as a means of generating guided waves in pipes or plates, by attaching a patch to a sample's surface. The effect of varying the applied static and dynamic magnetic field's amplitudes and directions and the frequency of the dynamic magnetic field was studied. It was demonstrated that the vibration of the magnetostrictive patch could be controlled and enhanced by optimizing the magnetic fields. It was also shown that for low-amplitude dynamic magnetic fields, Lorentz forces generated within the patch and the resonant frequency of the patch could also contribute to the enhancement of the vibration of the patch for low-amplitude fields. For high-amplitude dynamic magnetic fields, the magnetostriction effect can be the main transduction mechanism, which can be optimized for non-destructive testing and inspection purposes.

Modified FMCW Scheme for Improved Ultrasonic Positioning and Ranging of Unmanned Ground Vehicles at Distances < 50 mm

Unmanned ground vehicles (UGVs) find extensive use in various applications, including that within industrial environments. Efforts have been made to develop cheap, portable, and light-ranging/positioning systems to accurately locate their absolute/relative position and to automatically avoid potential obstacles and/or collisions with other drones. To this aim, a promising solution is the use of ultrasonic systems, which can be set up on UGVs and can potentially output a precise reconstruction of the drone's surroundings. In this framework, a so-called frequency-modulated continuous wave (FMCW) scheme is widely employed as a distance estimator. However, this technique suffers from low repeatability and accuracy at ranges of less than 50 mm when used in combination with low-resource hardware and commercial narrowband transducers, which is a distance range of the utmost importance to avoid potential collisions and/or imaging UGV surroundings. We hereby propose a modified FMCW-based scheme using an ad hoc time-shift of the reference signal. This was shown to improve performance at ranges below 50 mm while leaving the signal unaltered at greater distances. The capabilities of the modified FMCW were evaluated numerically and experimentally. A dramatic enhancement in performance was found for the proposed FMCW with respect to its standard counterpart, which is very close to that of the correlation approach. This work paves the way for the future use of FMCWs in applications requiring high precision.

A pilot study that provides evidence of epigenetic changes among mother-child pairs living proximal to mining in the US.

Environmental exposures to chemicals can disrupt gene expression, and the effects could be mediated by methylation. This investigation focused on methylation of genes associated with exposure to metals. Mother-child pairs from three locations in Montana were recruited, and buccal cells were collected for genome-wide methylation assay. Four pairs were from Butte, where there is mining and a Superfund site, four pairs were from Anaconda with a Superfund site, and four pairs were from Missoula with neither a mine nor a Superfund site. Principal component analysis, linear mixed models, hierarchical clustering and heatmap, and gene set enrichment analysis were used to visualize the profiles, identify the top associated methylation loci, and investigate the involved pathways. Distinctly higher or lower methylation in samples from Butte were found at the top differentially methylated loci. The 200 genes harboring the most hypermethylated loci were significantly enriched in genes involved in actin cytoskeleton regulation, ABC transporters, leukocyte transendothelial migration, focal adhesion, and adherens junction, which plays a role in pathogenesis of disease, including autism spectrum disorders. This study lays a foundation for inquiry about genetic changes associated with environmental exposure to metals for people living in proximity to Superfund and open pit mining.

Alphaproteobacteria facilitate Trichodesmium community trimethylamine utilization.

In the surface waters of the warm oligotrophic ocean, filaments and aggregated colonies of the nitrogen (N)-fixing cyanobacterium Trichodesmium create microscale nutrient-rich oases. These hotspots fuel primary productivity and harbour a diverse consortium of heterotrophs. Interactions with associated microbiota can affect the physiology of Trichodesmium, often in ways that have been predicted to support its growth. Recently, it was found that trimethylamine (TMA), a globally abundant organic N compound, inhibits N2 fixation in cultures of Trichodesmium without impairing growth rate, suggesting that Trichodesmium can use TMA as an alternate N source. In this study, 15 N-TMA DNA stable isotope probing (SIP) of a Trichodesmium enrichment was employed to further investigate TMA metabolism and determine whether TMA-N is incorporated directly or secondarily via cross-feeding facilitated by microbial associates. Herein, we identify two members of the marine Roseobacter clade (MRC) of Alphaproteobacteria as the likely metabolizers of TMA and provide genomic evidence that they converted TMA into a more readily available form of N, e.g., ammonium (NH4 + ), which was subsequently used by Trichodesmium and the rest of the community. The results implicate microbiome-mediated carbon (C) and N transformations in modulating N2 fixation and thus highlight the involvement of host-associated heterotrophs in global biogeochemical cycling.

Holey-structured tungsten metamaterials for broadband ultrasonic sub-wavelength imaging in water.

Metamaterials exhibiting Fabry-Pérot resonances are shown to achieve ultrasonic imaging of a sub-wavelength aperture in water immersion across a broad bandwidth. Holey-structured metamaterials of different thickness were additively manufactured using a tungsten substrate and selective laser melting, tungsten being chosen so as to create a significant acoustic impedance mismatch with water. Both broadband metamaterial behavior and sub-wavelength imaging in water are demonstrated experimentally and validated with finite element simulations over the 200-300 kHz range.

Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches.

The characteristics of removable magnetostrictive thin patches are investigated for the generation of guided waves in plates. The directivity patterns of SH, S0 and A0 modes have been measured in a thin metallic plate for different combinations of static and dynamic magnetic field directions. This used different coil geometries such as racetrack and spiral coils to generate the dynamic magnetic field, as well as separate biasing static magnetic fields from permanent magnets. This arrangement generated signals via both Lorentz and magnetostrictive forces, and the resultant emitted guided waves were studied for different dynamic and static magnetic field directions and magnitudes. It is demonstrated that different guided wave modes can be produced by controlling these parameters.

Ultrasonic Propagation in Highly Attenuating Insulation Materials.

Experiments have been performed to demonstrate that ultrasound in the 100-400 kHz frequency range can be used to propagate signals through various types of industrial insulation. This is despite the fact that they are highly attenuating to ultrasonic signals due to scattering and viscoelastic effects. The experiments used a combination of piezocomposite transducers and pulse compression processing. This combination allowed signal-to-noise levels to be enhanced so that signals reflected from the surface of an insulated and cladded steel pipe could be obtained.

Marine Synechococcus isolates representing globally abundant genomic lineages demonstrate a unique evolutionary path of genome reduction without a decrease in GC content.

Synechococcus, a genus of unicellular cyanobacteria found throughout the global surface ocean, is a large driver of Earth's carbon cycle. Developing a better understanding of its diversity and distributions is an ongoing effort in biological oceanography. Here, we introduce 12 new draft genomes of marine Synechococcus isolates spanning five clades and utilize ~100 environmental metagenomes largely sourced from the TARA Oceans project to assess the global distributions of the genomic lineages they and other reference genomes represent. We show that five newly provided clade-II isolates are by far the most representative of the recovered in situ populations (most 'abundant') and have biogeographic distributions distinct from previously available clade-II references. Additionally, these isolates form a subclade possessing the smallest genomes yet identified of the genus (2.14 ± 0.05Mbps; mean ± 1SD) while concurrently hosting some of the highest GC contents (60.67 ± 0.16%). This is in direct opposition to the pattern in Synechococcus's nearest relative, Prochlorococcus - wherein decreasing genome size has coincided with a strong decrease in GC content - suggesting this new subclade of Synechococcus appears to have convergently undergone genomic reduction relative to the rest of the genus, but along a fundamentally different evolutionary trajectory.

Ocean acidification increases iodine accumulation in kelp-based coastal food webs.

Kelp are main iodine accumulators in the ocean, and their growth and photosynthesis are likely to benefit from elevated seawater CO2 levels due to ocean acidification. However, there are currently no data on the effects of ocean acidification on iodine metabolism in kelp. As key primary producers in coastal ecosystems worldwide, any change in their iodine metabolism caused by climate change will potentially have important consequences for global geochemical cycles of iodine, including iodine levels of coastal food webs that underpin the nutrition of billions of humans around the world. Here, we found that elevated pCO2 enhanced growth and increased iodine accumulation not only in the model kelp Saccharina japonica using both short-term laboratory experiment and long-term in situ mesocosms, but also in several other edible and ecologically significant seaweeds using long-term in situ mesocosms. Transcriptomic and proteomic analysis of S. japonica revealed that most vanadium-dependent haloperoxidase genes involved in iodine efflux during oxidative stress are down-regulated under increasing pCO2 , suggesting that ocean acidification alleviates oxidative stress in kelp, which might contribute to their enhanced growth. When consumed by abalone (Haliotis discus), elevated iodine concentrations in S. japonica caused increased iodine accumulation in abalone, accompanied by reduced synthesis of thyroid hormones. Thus, our results suggest that kelp will benefit from ocean acidification by a reduction in environmental stress however; iodine levels, in kelp-based coastal food webs will increase, with potential impacts on biogeochemical cycles of iodine in coastal ecosystems.

Methods for Measuring Multiple Medication Adherence: A Systematic Review-Report of the ISPOR Medication Adherence and Persistence Special Interest Group.

BACKGROUND: A broad literature base exists for measuring medication adherence to monotherapeutic regimens, but publications are less extensive for measuring adherence to multiple medications. OBJECTIVES: To identify and characterize the multiple medication adherence (MMA) methods used in the literature. METHODS: A literature search was conducted using PubMed, PsycINFO, the International Pharmaceutical Abstracts, the Cumulative Index to Nursing and Allied Health Literature and the Cochrane Library databases on methods used to measure MMA published between January 1973 and May 2015. A two-step screening process was used; all abstracts were screened by pairs of researchers independently, followed by a full-text review identifying the method for calculating MMA. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed to conduct this systematic review. For studies that met the eligibility criteria, general study and adherence-specific characteristics and the number and type of MMA measurement methods were summarized. RESULTS: The 147 studies that were included originated from 32 countries, in 13 disease states. Of these studies, 26 used proportion of days covered, 23 used medication possession ratio, and 72 used self-reported questionnaires (e.g., the Morisky Scale) to assess MMA. About 50% of the studies included more than one method for measuring MMA, and different variations of medication possession ratio and proportion of days covered were used for measuring MMA. CONCLUSIONS: There appears to be no standardized method to measure MMA. With an increasing prevalence of polypharmacy, more efforts should be directed toward constructing robust measures suitable to evaluate adherence to complex regimens. Future research to understand the validity and reliability of MMA measures and their effects on objective clinical outcomes is also needed.

Molecular and physiological evidence of genetic assimilation to high CO2 in the marine nitrogen fixer Trichodesmium.

Most investigations of biogeochemically important microbes have focused on plastic (short-term) phenotypic responses in the absence of genetic change, whereas few have investigated adaptive (long-term) responses. However, no studies to date have investigated the molecular progression underlying the transition from plasticity to adaptation under elevated CO2 for a marine nitrogen-fixer. To address this gap, we cultured the globally important cyanobacterium Trichodesmium at both low and high CO2 for 4.5 y, followed by reciprocal transplantation experiments to test for adaptation. Intriguingly, fitness actually increased in all high-CO2 adapted cell lines in the ancestral environment upon reciprocal transplantation. By leveraging coordinated phenotypic and transcriptomic profiles, we identified expression changes and pathway enrichments that rapidly responded to elevated CO2 and were maintained upon adaptation, providing strong evidence for genetic assimilation. These candidate genes and pathways included those involved in photosystems, transcriptional regulation, cell signaling, carbon/nitrogen storage, and energy metabolism. Conversely, significant changes in specific sigma factor expression were only observed upon adaptation. These data reveal genetic assimilation as a potentially adaptive response of Trichodesmium and importantly elucidate underlying metabolic pathways paralleling the fixation of the plastic phenotype upon adaptation, thereby contributing to the few available data demonstrating genetic assimilation in microbial photoautotrophs. These molecular insights are thus critical for identifying pathways under selection as drivers in plasticity and adaptation.