A model of time-dependent macromolecular and elemental composition of phytoplankton.

Phytoplankton Chl:C:N:P ratios are important from both an ecological and a biogeochemical perspective. We show that these elemental ratios can be represented by a phytoplankton physiological model of low complexity that includes major cellular macromolecular pools. In particular, our model resolves time-dependent intracellular pools of chlorophyll, proteins, nucleic acids, carbohydrates/lipids, and N and P storage.

AAV6 mediated Gsx1 expression in neural stem progenitor cells promotes neurogenesis and restores locomotor function after contusion spinal cord injury.

Genomic screened homeobox 1 (Gsx1 or Gsh1) is a neurogenic transcription factor required for the generation of excitatory and inhibitory interneurons during spinal cord development. In the adult, lentivirus (LV) mediated Gsx1 expression promotes neural regeneration and functional locomotor recovery in a mouse model of lateral hemisection spinal cord injury (SCI). The LV delivery method is clinically unsafe due to insertional mutations to the host DNA.

Genomic architecture constrains macromolecular allocation in dinoflagellates.

Dinoflagellate genomes have a unique architecture that may constrain their physiological and biochemical responsiveness to environmental stressors. Here we quantified how nitrogen (N) starvation influenced macromolecular allocation and C:N:P of three photosynthetic marine dinoflagellates, representing different taxonomic classes and genome sizes. Dinoflagellates respond to nitrogen starvation by decreasing cellular nitrogen, protein and RNA content, but unlike many other eukaryotic phytoplankton examined RNA:protein is invariant.

Common environmental stress responses in a model marine diatom.

Marine planktonic diatoms are among the most important contributors to phytoplankton blooms and marine net primary production. Their ecological success has been attributed to their ability to rapidly respond to changing environmental conditions. Here, we report common molecular mechanisms used by the model marine diatom Thalassiosira pseudonana to respond to 10 diverse environmental stressors using RNA-Seq analysis.

Elemental stoichiometry of the key calcifying marine phytoplankton Emiliania huxleyi under ocean climate change: A meta-analysis.

The elemental composition of marine microorganisms (their C:N:P ratio, or stoichiometry) is central to understanding the biotic and biogeochemical processes underlying key marine ecosystem functions. Phytoplankton C:N:P is species specific and flexible to changing environmental conditions. However, bulk or fixed phytoplankton stoichiometry is usually assumed in biogeochemical and ecological models because more realistic, environmentally responsive C:N:P ratios have yet to be defined for key functional groups.

Current Advancements in Spinal Cord Injury Research-Glial Scar Formation and Neural Regeneration.

Spinal cord injury (SCI) is a complex tissue injury resulting in permanent and degenerating damage to the central nervous system (CNS). Detrimental cellular processes occur after SCI, including axonal degeneration, neuronal loss, neuroinflammation, reactive gliosis, and scar formation. The glial scar border forms to segregate the neural lesion and isolate spreading inflammation, reactive oxygen species, and excitotoxicity at the injury epicenter to preserve surrounding healthy tissue.

Machine-Assisted Discovery of Chondroitinase ABC Complexes toward Sustained Neural Regeneration.

Among the many molecules that contribute to glial scarring, chondroitin sulfate proteoglycans (CSPGs) are known to be potent inhibitors of neuronal regeneration. Chondroitinase ABC (ChABC), a bacterial lyase, degrades the glycosaminoglycan (GAG) side chains of CSPGs and promotes tissue regeneration. However, ChABC is thermally unstable and loses all activity within a few hours at 37 °C under dilute conditions.

Basin-scale biogeography of marine phytoplankton reflects cellular-scale optimization of metabolism and physiology.

Extensive microdiversity within , the most abundant marine cyanobacterium, occurs at scales from a single droplet of seawater to ocean basins. To interpret the structuring role of variations in genetic potential, as well as metabolic and physiological acclimation, we developed a mechanistic constraint-based modeling framework that incorporates the full suite of genes, proteins, metabolic reactions, pigments, and biochemical compositions of 69 sequenced isolates spanning the pangenome. Optimizing each strain to the local, observed physical and chemical environment along an Atlantic Ocean transect, we predicted variations in strain-specific patterns of growth rate, metabolic configuration, and physiological state, defining subtle niche subspaces directly attributable to differences in their encoded metabolic potential.

Diversity of Adult Neural Stem and Progenitor Cells in Physiology and Disease.

Adult neural stem and progenitor cells (NSPCs) contribute to learning, memory, maintenance of homeostasis, energy metabolism and many other essential processes. They are highly heterogeneous populations that require input from a regionally distinct microenvironment including a mix of neurons, oligodendrocytes, astrocytes, ependymal cells, NG2+ glia, vasculature, cerebrospinal fluid (CSF), and others. The diversity of NSPCs is present in all three major parts of the CNS, i.

Nkx6.1 enhances neural stem cell activation and attenuates glial scar formation and neuroinflammation in the adult injured spinal cord.

Nkx6.1 plays an essential role during the embryonic development of the spinal cord. However, its role in the adult and injured spinal cord is not well understood.

Contrasting transcriptomic responses of a microbial eukaryotic community to oil and dispersant.

Dispersants can aid dispersion and biodegradation of oil in seawater, but the wider ecotoxicological effects of oil and dispersant to the base of marine food webs is unclear. Here we apply a metatranscriptomic approach to identify molecular responses of a natural marine microbial eukaryotic community to oil and chemically dispersed oil. Oil exposure stimulated the upregulation of ketogenesis in the eukaryotic community, which may alleviate carbon- and energy-limitation and reduce oxidative stress.

Gsx1 promotes locomotor functional recovery after spinal cord injury.

Promoting residential cells, particularly endogenous neural stem and progenitor cells (NSPCs), for tissue regeneration represents a potential strategy for the treatment of spinal cord injury (SCI). However, adult NSPCs differentiate mainly into glial cells and contribute to glial scar formation at the site of injury. Gsx1 is known to regulate the generation of excitatory and inhibitory interneurons during embryonic development of the spinal cord.

Anthropogenic climate change impacts on copepod trait biogeography.

Copepods are among the most abundant marine metazoans and form a key link between marine primary producers, higher trophic levels, and carbon sequestration pathways. Climate change is projected to change surface ocean temperature by up to 4°C in the North Atlantic with many associated changes including slowing of the overturning circulation, areas of regional freshening, and increased salinity and reductions in nutrients available in the euphotic zone over the next century. These changes will lead to a restructuring of phytoplankton and zooplankton communities with cascading effects throughout the food web.

Dynamic Photophysiological Stress Response of a Model Diatom to Ten Environmental Stresses.

Stressful environmental conditions can induce many different acclimation mechanisms in marine phytoplankton, resulting in a range of changes in their photophysiology. Here we characterize the common photophysiological stress response of the model diatom Thalassiosira pseudonana to ten environmental stressors and identify diagnostic responses to particular stressors. We quantify the magnitude and temporal trajectory of physiological parameters including the functional absorption cross-section of PSII (σ ), quantum efficiency of PSII, non-photochemical quenching (NPQ), cell volume, Chl a, and carotenoid (Car) content in response to nutrient starvation (nitrogen (N), phosphorus (P), silicon (Si), and iron (Fe)), changes in temperature, irradiance, pH, and reactive oxygen species (ROS) over 5 time points (0, 2, 6, 24, 72 h).

Quantifying nutrient throughput and DOM production by algae in continuous culture.

Freshwater and marine algae can balance nutrient demand and availability by regulating uptake, accumulation and exudation. To obtain insight into these processes under nitrogen (N) and phosphorus (P) limitation, we reanalyze published data from continuous cultures of the chlorophyte Selenastrum minutum. Based on mass budgets, we argue that much of the non-limiting N and P had passed through the organisms and was present as dissolved organic phosphorus or nitrogen (DOP or DON).

Trait-dependent variability of the response of marine phytoplankton to oil and dispersant exposure.

The Deepwater Horizon oil spill released millions of barrels of crude oil into the Gulf of Mexico, and saw widespread use of the chemical dispersant Corexit. We assessed the role of traits, such as cell size, cell wall, motility, and mixotrophy on the growth and photosynthetic response of 15 phytoplankton taxa to oil and Corexit. We collected growth and photosynthetic data on five algal cultures.

A ribosomal sequence-based oil sensitivity index for phytoplankton groups.

Species-level variability has made it difficult to determine the relative sensitivity of phytoplankton to oil and mixtures of oil and dispersant. Here we develop a phytoplankton group sensitivity index using ribosome sequence data that we apply to a mesocosm experiment in which a natural microbial community was exposed to oil and two oil-dispersant mixtures. The relative sensitivity of four phytoplankton taxonomic groups, diatoms, dinoflagellates, green algae, and Chrysophytes, was computed using the log of the ratio of the number of species that increase to the number that decrease in relative abundance in the treatment relative to the control.

Correction: Nitrogen starvation induces distinct photosynthetic responses and recovery dynamics in diatoms and prasinophytes.

[This corrects the article DOI: 10.1371/journal.pone.

The macromolecular composition of noncalcified marine macroalgae.

The macromolecular composition of macroalgae influences nutrient flow and food quality in aquatic ecosystems and the value of macroalgae species for human consumption, aquaculture, biofuels, and other applications. We used literature data (125 publications, 1,117 observations) and a hierarchal Bayesian statistical model to estimate the average macromolecular composition, protein, lipid, and carbohydrate of macroalgae as a whole and at the phylum level. Our focus was on marine, noncalcified macroalgae sampled from wild-grown populations in the field.