Biology subjects

Polka, J. K.

Publications and source records attributed to Polka, J. K..

7 recordsLinked to original sources

bioRxiv2021

The DocMaps Framework for representing assertions on research products in an extensible, machine-readable, and discoverable format

Peer review of a research product varies widely depending on the publishers and platforms involved in the process. As scholarly publishing is disrupted by new innovations, peer review processes become more heterogeneous, placing an increasing burden on the researcher in understanding how they can communicate their scholarship. New ways to model such processes, and increase transparency, trust, and experimentation in scholarly publishing are needed. Many are emerging but can tend to focus on the needs of creators, and not those of readers, funders, and the whole scholarly publishing ecosystem. They may not place focus on representing editorial practices in ways that can be reliably aggregated, surfaced, and queried; are often limited to traditional peer review processes; and cannot capture the full range of editorial practices and events needed to accommodate alternative publication, review, and curation models. To support researchers in a world of experimentation in scholarly publishing, we propose a machine-readable, extensible, and discoverable framework for representing and surfacing review and editorial processes. Working with a Technical Committee composed of interested parties by employing a modified Delphi Method, we developed initial guiding principles and proposals towards an object-level editorial metadata framework compatible with a broad range of possible futures for scholarly publishing. We present the results of this process with a proposal and example use cases for DocMaps, a framework for representing object-level assertions.

scientific communication and education↗

bioRxiv2021

Preprints in motion: tracking changes between posting and journal publication

Amidst the COVID-19 pandemic, preprints in the biomedical sciences are being posted and accessed at unprecedented rates, drawing widespread attention from the general public, press and policymakers for the first time. This phenomenon has sharpened longstanding questions about the reliability of information shared prior to journal peer review. Does the information shared in preprints typically withstand the scrutiny of peer review, or are conclusions likely to change in the version of record? We assessed preprints from bioRxiv and medRxiv that had been posted and subsequently published in a journal through 30th April 2020, representing the initial phase of the pandemic response. We utilised a combination of automatic and manual annotations to quantify how an article changed between the preprinted and published version. We found that the total number of figure panels and tables changed little between preprint and published articles. Moreover, the conclusions of 7.2% of non-COVID-19-related and 17.2% of COVID-19-related abstracts undergo a discrete change by the time of publication, but the majority of these changes do not qualitatively change the conclusions of the paper.

scientific communication and education↗

bioRxiv2020

Preprinting a pandemic: the role of preprints in the COVID-19 pandemic

The world continues to face a life-threatening viral pandemic. The virus underlying the COVID-19 disease, SARS-CoV-2, has caused over 98 million confirmed cases and 2.2 million deaths since January 2020. Although the most recent respiratory viral pandemic swept the globe only a decade ago, the way science operates and responds to current events has experienced a paradigm shift in the interim. The scientific community has responded rapidly to the COVID-19 pandemic, releasing over 125,000 COVID-19 related scientific articles within 10 months of the first confirmed case, of which more than 30,000 were hosted by preprint servers. We focused our analysis on bioRxiv and medRxiv, two growing preprint servers for biomedical research, investigating the attributes of COVID-19 preprints, their access and usage rates, as well as characteristics of their propagation on online platforms. Our data provides evidence for increased scientific and public engagement with preprints related to COVID-19 (COVID-19 preprints are accessed more, cited more, and shared more on various online platforms than non-COVID-19 preprints), as well as changes in the use of preprints by journalists and policymakers. We also find evidence for changes in preprinting and publishing behaviour: COVID-19 preprints are shorter and reviewed faster. Our results highlight the unprecedented role of preprints and preprint servers in the dissemination of COVID-19 science, and the impact of the pandemic on the scientific communication landscape.

scientific communication and education↗

bioRxiv2020

A systematic examination of preprint platforms for use in the medical and biomedical sciences setting

ABSTRACTObjectives The objective of this review is to identify all preprint platforms with biomedical and medical scope and to compare and contrast the key characteristics and policies of these platforms. We also aim to provide a searchable database to enable relevant stakeholders to compare between platforms.Study Design and Setting Preprint platforms that were launched up to 25th June 2019 and have a biomedical and medical scope according to MEDLINE’s journal selection criteria were identified using existing lists, web-based searches and the expertise of both academic and non-academic publication scientists. A data extraction form was developed, pilot-tested and used to collect data from each preprint platform’s webpage(s). Data collected were in relation to scope and ownership; content-specific characteristics and information relating to submission, journal transfer options, and external discoverability; screening, moderation, and permanence of content; usage metrics and metadata. Where possible, all online data were verified by the platform owner or representative by correspondence.Results A total of 44 preprint platforms were identified as having biomedical and medical scope, 17 (39%) were hosted by the Open Science Framework preprint infrastructure, six (14%) were provided by F1000 Research Ltd (the Open Research Central infrastructure) and 21 (48%) were other independent preprint platforms. Preprint platforms were either owned by non-profit academic groups, scientific societies or funding organisations (n=28; 64%), owned/partly owned by for-profit publishers or companies (n=14; 32%) or owned by individuals/small communities (n=2; 5%). Twenty-four (55%) preprint platforms accepted content from all scientific fields although some of these had restrictions relating to funding source, geographical region or an affiliated journal’s remit. Thirty-three (75%) preprint platforms provided details about article screening (basic checks) and 14 (32%) of these actively involved researchers with context expertise in the screening process. The three most common screening checks related to the scope of the article, plagiarism and legal/ethical/societal issues and compliance. Almost all preprint platforms allow submission to any peer-reviewed journal following publication, have a preservation plan for read-access, and most have a policy regarding reasons for retraction and the sustainability of the service. Forty-one (93%) platforms currently have usage metrics, with the most common metric being the number of downloads presented on the abstract page.Conclusion A large number of preprint platforms exist for use in biomedical and medical sciences, all of which offer researchers an opportunity to rapidly disseminate their research findings onto an open-access public server, subject to scope and eligibility. However, the process by which content is screened before online posting and withdrawn or removed after posting varies between platforms, which may be associated with platform operation, ownership, governance and financing.In concurrence with an increase in the number of preprint servers and platforms supporting biomedical and medical sciences research since 2013, there has been substantial growth in the number of preprints posted in this research area.The significant benefits of accelerated dissemination of research that preprints offer has attracted the support of many major funders.The raised profile of preprints has led to their wider acceptance in institutional and individual level assessment.This is the first full examination of the characteristics and policies of 44 preprint platforms with biomedical and medical scope. We use a robust methodological approach to extract relevant information from web-based material with input from preprint platform owners.Despite concerns regarding the permanence and quality of preprints, most preprint platforms have long-term preservation strategies and many have screening checks (for example, a basic check for the relevance of content) in place. For some platforms, these checks are performed by researchers with content expertise.We provide a searchable database as a valuable resource for researchers, funders and policymakers in the biomedical and medical science field to determine which preprint platforms are relevant to their research scope and which have the functionality and policies that they value most.Competing Interest StatementJessica Polka is Executive Director of ASAPbio.View Full Text

scientific communication and education↗

bioRxiv2017

Cryo-EM structure of the bacterial actin AlfA reveals unique assembly and ATP-binding interactions and the absence of a conserved subdomain

Bacterial actins are an evolutionarily diverse family of ATP-dependent filaments built from protomers with a conserved structural fold. Actin-based segregation systems are encoded on many bacterial plasmids and function to partition plasmids into daughter cells. The bacterial actin AlfA segregates plasmids by a mechanism distinct from other partition systems, dependent on its unique dynamic properties. Here, we report the near-atomic resolution cryo-EM structure of the AlfA filament, which reveals a strikingly divergent filament architecture resulting from the loss of a subdomain conserved in all other actins and a novel mode of ATP binding. Its unusual assembly interfaces and nucleotide interactions provide insight into AlfA dynamics, and expand the range of evolutionary variation accessible to actin quaternary structure.\n\nSignificance StatementActin filaments are dynamic cytoskeletal elements that assemble upon ATP binding. Actin homologs are present in all domains of life, and all share a similar three-dimensional structure of the assembling subunit, but evolutionary changes to subunit have generated many different actin filament structures. The filament structure of the bacterial actin AlfA, which positions plasmids - small, circular DNA molecules that encode important genes - to ensure that each daughter cell receives a copy at cell division. AlfA is different from all other actins in two critical ways: it binds to ATP in a unique way, and it is missing a quarter of the conserved structural core. These differences explain unusual AlfA assembly dynamics that underlie its ability to move plasmids.

biophysics↗

bioRxiv2017

Bacterial Microtubules Exhibit Polarized Growth, Mixed-Polarity Bundling, and Destabilization by GTP Hydrolysis

Bacteria of the genus Prosthecobacter express homologs of eukaryotic -and {beta}-tubulin, called BtubA and BtubB, that have been observed to assemble into bacterial microtubules (bMTs). The btubAB genes likely entered the Prosthecobacter lineage via horizontal gene transfer and may derive from an early ancestor of the modern eukaryotic microtubule (MT). Previous biochemical studies revealed that BtubA/B polymerization is GTP-dependent and reversible and that BtubA/B folding does not require chaperones. To better understand bMT behavior and gain insight into the evolution of microtubule dynamics, we characterized in vitro bMT assembly using a combination of polymerization kinetics assays, and microscopy. Like eukaryotic microtubules, bMTs exhibit polarized growth with different assembly rates at each end. GTP hydrolysis stimulated by bMT polymerization drives a stochastic mechanism of bMT disassembly that occurs via polymer breakage. We also observed treadmilling (continuous addition and loss of subunits at opposite ends) of bMT fragments. Unlike MTs, polymerization of bMTs requires KCl, which reduces the critical concentration for BtubA/B assembly and induces bMTs to form stable mixed-orientation bundles in the absence of any additional bMT-binding proteins. Our results suggest that at potassium concentrations resembling that inside the cytoplasm of Prosthecobacter, bMT stabilization through self-association may be a default behavior. The complex dynamics we observe in both stabilized and unstabilized bMTs may reflect common properties of an ancestral eukaryotic tubulin polymer.\n\nImportanceMicrotubules are polymers within all eukaryotic cells that perform critical functions: they segregate chromosomes in cell division, organize intracellular transport by serving as tracks for molecular motors, and support the flagella that allow sperm to swim. These functions rely on microtubules remarkable range of tunable dynamic behaviors. Recently discovered bacterial microtubules composed of an evolutionarily related protein are evolved from a missing link in microtubule evolution, the ancestral eukaryotic tubulin polymer. Using microscopy and biochemical approaches to characterize bacterial microtubules, we observed that they exhibit complex and structurally polarized dynamic behavior like eukaryotic microtubules, but differ in how they self-associate into bundles and become destabilized. Our results demonstrate the diversity of mechanisms that microtubule-like filaments employ to promote filament dynamics and monomer turnover.

microbiology↗

bioRxiv2016

Super-resolution microscopy of the β-carboxysome reveals a homogenous matrix

Carbon fixation in cyanobacteria makes a major contribution to the global carbon cycle. The cyanobacterial carboxysome is a proteinaceous microcompartment that protects and concentrates the carbon-fixing enzyme RuBisCO in a paracrystalline lattice, making it possible for these organisms to fix CO2 from the atmosphere. The protein responsible for the organization of this lattice in beta-type carboxysomes of the freshwater cyanobacterium Synechococcus elongatus, CcmM, occurs in two isoforms thought to localize differentially within the carboxysome matrix. Here we use widefield timelapse and 3D-structured illumination microscopy (3D-SIM) to study the recruitment and localization of these two isoforms. We demonstrate that this super-resolution technique is capable of successfully resolving the outer protein shell of the carboxysome from its internal cargo. We develop an automated analysis pipeline to analyze and quantify 3D-SIM images and generate a population level description of carboxysome shell protein, RuBisCO, and CcmM isoform localization. We find that both CcmM isoforms colocalize in space and time, prompting a revised model of the internal arrangement of the beta carboxysome.

cell biology↗