Heterotrophic bacteria exhibit a wide range of rates of extracellular production and decay of hydrogen peroxide

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bond, R. J., Hansel, C. M., & Voelker, B. M. Heterotrophic bacteria exhibit a wide range of rates of extracellular production and decay of hydrogen peroxide. Frontiers in Marine Science, 7, (2020): 72, doi:10.3389/fmars.2020.00072.Bacteria have been implicated as both a source and sink of hydrogen peroxide (H2O2), a reactive oxygen species which can both impact microbial growth and participate in the geochemical cycling of trace metals and carbon in natural waters. In this study, simultaneous H2O2 production and decay by twelve species of heterotrophic bacteria were evaluated in both batch and flow-through incubations. While wide species-to-species variability of cell-normalized H2O2 decay rate coefficients [2 × 10–8 to 5 × 10–6 hr–1 (cell mL–1)–1] was observed, these rate coefficients were relatively consistent for a given bacterial species. By contrast, observed production rates (below detection limit to 3 × 102 amol cell–1 hr–1) were more variable even for the same species. Variations based on incubation conditions in some bacterial strains suggest that external conditions may impact extracellular H2O2 levels either through increased extracellular production or leakage of intracellular H2O2. Comparison of H2O2 production rates to previously determined superoxide (O2–) production rates suggests that O2– and H2O2 production are not necessarily linked. Rates measured in this study indicate that bacteria could account for a majority of H2O2 decay observed in aqueous systems but likely only make a modest contribution to dark H2O2 production.This research was supported by NSF grant OCE-1131734/1246174 to BV and CH

Inspiring Vision and Practice: CultureWork, a leading voice for arts and cultural management praxis

3 pagesIn this issue of CultureWork we take a moment to look back and reflect on the publication’s past. As part of this reflection we celebrate the legacy and history of arts management practice upon which we have focused. Over its 15 years of publication, CultureWork has consistently shared relevant, timely work from within the field of arts and cultural management, including emerging research and practical advisories

Expand+Functional selection and systematic analysis of intronic splicing elements identify active sequence motifs and associated splicing factors

Despite the critical role of pre-mRNA splicing in generating proteomic diversity and regulating gene expression, the sequence composition and function of intronic splicing regulatory elements (ISREs) have not been well elucidated. Here, we employed a high-throughput in vivo Screening PLatform for Intronic Control Elements (SPLICE) to identify 125 unique ISRE sequences from a random nucleotide library in human cells. Bioinformatic analyses reveal consensus motifs that resemble splicing regulatory elements and binding sites for characterized splicing factors and that are enriched in the introns of naturally occurring spliced genes, supporting their biological relevance. In vivo characterization, including an RNAi silencing study, demonstrate that ISRE sequences can exhibit combinatorial regulatory activity and that multiple trans-acting factors are involved in the regulatory effect of a single ISRE. Our work provides an initial examination into the sequence characteristics and function of ISREs, providing an important contribution to the splicing code

Calcification depth of deep-dwelling planktonic foraminifera from the eastern North Atlantic constrained by stable oxygen isotope ratios of shells from stratified plankton tows

Stable oxygen isotopes (delta O-18) of planktonic foraminifera are one of the most used tools to reconstruct environmental conditions of the water column. Since different species live and calcify at different depths in the water column, the delta O-18 of sedimentary foraminifera reflects to a large degree the vertical habitat and interspecies delta O-18 differences and can thus potentially provide information on the vertical structure of the water column. However, to fully unlock the potential of foraminifera as recorders of past surface water properties, it is necessary to understand how and under what conditions the environmental signal is incorporated into the calcite shells of individual species. Deep-dwelling species play a particularly important role in this context since their calcification depth reaches below the surface mixed layer. Here we report delta O-18 measurements made on four deep-dwelling Globorotalia species collected with stratified plankton tows in the eastern North Atlantic. Size and crust effects on the delta O-18 signal were evaluated showing that a larger size increases the delta O-18 of G. inflata and G. hirsuta, and a crust effect is reflected in a higher delta O-18 signal in G. truncatulinoides. The great majority of the delta O-18 values can be explained without invoking disequilibrium calcification. When interpreted in this way the data imply depth-integrated calcification with progressive addition of calcite with depth to about 300m for G. inflata and to about 500m for G. hirsuta. In G. scitula, despite a strong subsurface maximum in abundance, the vertical delta O-18 profile is flat and appears dominated by a surface layer signal. In G. truncatulinoides, the delta O-18 profile follows equilibrium for each depth, implying a constant habitat during growth at each depth layer. The delta O-18 values are more consistent with the predictions of the Shackleton (1974) palaeotemperature equation, except in G. scitula which shows values more consistent with the Kim and O'Neil (1997) prediction. In all cases, we observe a difference between the level where most of the specimens were present and the depth where most of their shell appears to calcify.Agência financiadora Portuguese Foundation for Science and Technology (FCT): SFRH/BD/78016/2011; UID/Multi/04326/2019 European Union Seventh Framework Programme (FP7/2007-2013): 228344-EUROFLEETS German Research Foundation (DFG): WA2175/2-1; WA2175/4-1 German Climate Modelling consortium PalMod - German Federal Ministry of Education and Research (BMBF)info:eu-repo/semantics/publishedVersio

Beam Dynamics Studies for SRF Photoinjectors

The SRF photoinjector combines the advantages of photo assisted production of high brightness, short electron pulses and high gradient, low loss continuous wave CW operation of a superconducting radiofrequency SRF cavity. The paper discusses beam dynamics considerations for ERL class applications of SRF photoinjectors. One case of particular interest is the design of the SRF photoinjector for BERLinPro, an ERL test facility demanding a high brightness beam with an emittance better than 1 mm mrad at 77 pC and average current of 100 m

Regulatory mechanisms of surfactant secretion

AbstractSurfactant secretion is a critical regulated process in the metabolism of pulmonary surfactant. Presumably, because this process is vital to the survival of the organism, there are several independent pathways for stimulating secretion which work through different cell surface receptors and signaling mechanisms. In addition, there is apparent homeostatic regulation in that two components of surfactant, namely SP-A and dipalmitoylphosphatidylcholine, can inhibit secretion. Although secretion of surfactant has been studied for over two decades, there remains some important issues to be resolved. In vivo secretion can be stimulated by hyperventilation or even a single large breath. However, we do not know the biochemical mechanism for this physiologically important form of stimulation. In vitro, we know many of the proximal events in signaling, but we do not know how the lamellar bodies move within a cell or the docking mechanism at the plasma membrane. Many investigators have demonstrated that SP-A will inhibit secretion in vitro, but the mechanism is not known. Finally, there is a route of secretion of SP-A independent of lamellar bodies, but we do not know details of this pathway nor its regulation

Wigner Glass, Spin-liquids, and the Metal-Insulator Transition

Recent experiments on the two dimensional electron gas in various semiconductor devices have revealed an unexpected metal-insulator transition and have challenged the previously held assumption that there is no such transition in two dimensions. While the experiments are still at the stage of rapid development, it is becoming evident that they cannot be understood from the conventional perspective of weak interactions. In the present paper, we propose the following. (1) The low-density insulating state is the Wigner Glass, a phase with quasi-long-range translational order and competing ferromagnetic and antiferromagnetic spin-exchange interactions. (2) The transition is the melting of this Wigner Glass, disorder being the agent allowing the transition to be second order. (3) Within the Wigner Glass phase, there are at least two, distinct magnetic ground-states, a ferromagnetic state at very low electron density and a spin-liquid state with a spin pseudo-gap at higher densities. (4) The metallic side of the transition is a non-Fermi liquid. These conclusions are encapsulated in Figure 1 which presents the proposed phase diagram as a function of disorder strength and density; we also suggest experimental signatures of the various phases and transitions.Comment: Revised manuscript 6 pages, 1 figure redrawn for clarity; discussion of experiments expande

Porelike Morphologies in Amyloidogenic Proteins

Intrinsically disordered proteins (IDPs) have been linked to a variety of human diseases. The roles that IDPs play in physiological functions and disease pathology are frequently an enigma. Their disordered nature and structural complexity presents significant experimental and computational challenges, and makes IDPs difficult to study and characterize effectively. Soluble, low molecular weight (LMW) oligomers of the IDPs amyloid beta-protein (Abeta) and alpha-synuclein (alphaS) have been hypothesized to be the primary neurotoxic agents in Alzheimer's Disease (AD) and Parkinson's Disease (PD) respectively, however their structure remains elusive. In this thesis, we take a varied computational approach in studies of Abeta and alphaS oligomers in order to probe and elucidate their structure. A$\beta$ oligomers have been observed to impair cognition in live rats and to negatively affect memory by hindering long-term potentiation in the hippocampus. Of the two predominant A$\beta$ alloforms, Abeta40 and Abeta42, the latter is more strongly associated with AD. Here, we structurally characterize Abeta40 and Abeta42 monomers through pentamers via a multi-scale computational approach, wherein conformations derived by discrete molecular dynamics combined with an implicit--solvent intermediate--resolution protein model and amino acid-specific interactions (DMD4B-HYDRA) were converted into all-atom conformations and subjected to explicit-solvent MD. Unlike the initial DMD4B-HYDRA conformations, fully atomistic Abeta40 and Abeta42 trimers, tetramers, and pentamers form water-permeable pores, whereby the tendency for pore formation sharply increases with oligomer order and is the highest for Abeta42 pentamers. Our findings reveal an extraordinary ability of Abeta oligomers to form pores in pure water prior to their insertion into a membrane. PD is characterized in part by the cerebral accumulation of alpha-synuclein, a 140 amino acids--long protein produced naturally in the body, into abnormal intracellular protein deposits in the brain. Soluble alphaS oligomers in particular have been shown to be toxic to neuronal cell cultures in vitro. We here characterize the structure of alphaS oligomers computationally using the DMD4B-HYDRA approach. We vary the implicit-solvent parameter corresponding to the strength of electrostatic interactions (E_CH) to fine tune the solvent conditions in order to obtain an alphaS oligomer distribution consistent with experimental data. The population of alphaS oligomers is characterized by a monotonically decreasing propensity of monomers through septamers followed by an increase in octamers. We observe that alphaS forms water-permeable pores in all assembly states, with a propensity for pore formation that increases with oligomer order. Previous studies have reported that both Abeta and alphaS oligomers form ion channels when embedded into a cellular membrane, which causes an abnormal ion flux and eventually leads to cell death. These observations form a leading theory for the mechanism behind the cytotoxicity associated with AD and PD, known as the ion channel hypothesis. The observations of porelike morphologies in our studies of LMW oligomers of Abeta and alphaS, which form in the absence of a membrane and increase in propensity with oligomer order, provides important insights and further support to the ion channel hypothesis of AD and PD.Ph.D., Physics -- Drexel University, 201