Biology subjects

Lopez, D.

Publications and source records attributed to Lopez, D..

At least 19 recordsLinked to original sources

bioRxiv2026

Chronic cocaine exposure negatively impacts Long-COVID-like outcomes produced by the SARS-CoV-2 spike protein in the rat

Acute COVID-19 outcomes are exacerbated by substance use, however, the impact of substance use on Long-COVID is unknown. Here, we investigated the impact of chronic cocaine administration on spike-induced Long-COVID-like outcomes in the rat. Rats received intermittent chronic cocaine administration and a single intravenous injection of the SARS-CoV-2 spike protein. Two months following spike administration, Long-COVID-like outcomes were assessed. Exposure to spike protein in the presence of cocaine produced a persistent reduction in weight gain as compared with controls or spike protein alone. Further, cocaine-treated rats exposed to spike had lower withdrawal thresholds compared to control animals as well as their own baseline, suggesting increased pain sensitivity. Spike and/or cocaine increased the ratio of interleukin-6 (IL-6) to interleukin-10 (IL-10) levels in the hippocampus, indicating a shift towards a proinflammatory state. Paw withdrawal thresholds were positively correlated with IL-10 levels in the hippocampus and prefrontal cortex. Regarding olfaction, rats exposed to spike spent less time sniffing an odor attractant. Cocaine produced an anxiolytic-like phenotype during the elevated plus maze test. Further analysis of behaviors on the maze revealed that the latency to enter the open arms was shorter in rats exposed to spike or cocaine, suggesting a possible impulsive-like phenotype in these animals. These findings demonstrate the negative impact of cocaine on Long-COVID-like outcomes suggesting a need for increased clinical observations of people with co-occurring Long-COVID and cocaine use disorder. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=59 SRC="FIGDIR/small/729575v1_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@12fdc19org.highwire.dtl.DTLVardef@11b1b0dorg.highwire.dtl.DTLVardef@8d1e21org.highwire.dtl.DTLVardef@b53d20_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

In-Situ ssDNA Isolation from dsDNA Sources as a Streamlined Pathway to DNA Origami Assembly and Testing

Scaffolded DNA origami has become a valuable nanoscale tool for applications in biomedical and physical sciences. Critical to leveraging the modular and programmable properties of DNA origami nanodevices is access to the scaffold strand, a long single-stranded DNA (ssDNA) of precise length and sequence, which is folded into a compact shape via piecewise base-pairing with many staple strands, short ssDNA oligonucleotides. Current methods to produce and manipulate long ssDNA scaffolds can be costly, time-consuming, and cumbersome. In contrast, methods to produce and manipulate the sequence of double-stranded DNA (dsDNA) are efficient and scalable. Here, we present a method for the rapid isolation of target ssDNA sequences from a variety of dsDNA sources using oligonucleotides as blocking strands that bind continuously to the undesired strand, thereby releasing the target scaffold strand. We report successful ssDNA isolation from linear and supercoiled dsDNAs of various sequences and lengths, ranging from 769 to 15,101 nucleotides. In addition to isolating ssDNA, we demonstrated this approach enables folding of DNA origami directly from dsDNA templates using both blocking and staple strands in a single-pot thermally controlled reaction. Furthermore, we explore multi-scaffold and gene-encoding DNA origami structures, expanding the framework for application-based designs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/709872v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@f7ada7org.highwire.dtl.DTLVardef@a9bab8org.highwire.dtl.DTLVardef@121b695org.highwire.dtl.DTLVardef@5a1dea_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2025

Fronto-Parietal Oscillatory Dynamics of Emotion Regulation as a Function of Adult Attachment Orientations

Emotion regulation enables individuals to modulate emotional experiences and behaviors according to situational demands. Within attachment theory, individual differences in attachment anxiety and avoidance are conceived as interpersonal dispositions that influence the quality and efficiency of emotion regulation strategies, potentially shaping the underlying neural dynamics. This study examined cortical oscillatory activity during two regulation strategies--cognitive reappraisal and expressive suppression--focusing on theta (4-8 Hz) and beta (15-30 Hz) bands at the source level. Forty adults (21 male, 18 female, 1 gender-unspecified; M = 27.58 years, SD = 8.71) performed an emotion regulation task involving emotionally evocative images from the International Affective Picture System (IAPS) while EEG was recorded. Cortical sources were reconstructed using standardized low-resolution brain electromagnetic tomography (sLORETA). Linear mixed-effects models (LMMs) assessed the effects of condition, region of interest (ROI), and attachment orientations on oscillatory power. Results showed that higher attachment anxiety predicted reduced theta power in the right dorsolateral prefrontal cortex (dlPFC) during reappraisal, indicating attenuated recruitment of cognitive control mechanisms. In the beta band, suppression reduced activity in the right parietal lobe/precuneus -- a region involved in self-referential and attentional processes -- across participants, while during reappraisal, attachment anxiety was linked to lower beta power and attachment avoidance to higher beta power in the left dlPFC. Together, these findings indicate that cognitive reappraisal and expressive suppression engage distinct cortical oscillatory systems, and that interpersonal dispositions modulate their neural implementation. Frontal theta appears to index top-down control during reappraisal, whereas beta activity shows a dual pattern: frontal beta variations reflect differences in control stability associated with attachment orientations, and parietal beta decreases during suppression suggest attentional disengagement from self-referential processing.

neuroscience↗

bioRxiv2025

Localized immunomodulation with cytokine-producing cells to mitigate host immune rejection responses in rodents and a non-human primate

The efficacy of cell-based therapeutics is often compromised by host immune recognition of implanted cells and biomaterials, resulting in fibrotic encapsulation and loss of function. Here, we address this challenge with an immunomodulatory cell-based therapy, in which alginate-encapsulated retinal pigment epithelial cells continuously secrete cytokines to locally modulate the implant microenvironment. In a healthy rodent model, the localized production of interleukin-10 (IL-10) or IL-12 from encapsulated cytokine-producing cells prevented host immune rejection and fibrosis of alginate capsules. Mechanistically, treatment was associated with reduced expression of pro-fibrotic genes and immune shifts consistent with macrophage and T-cell regulation, supporting a cytokine-mediated mitigation of foreign body response. In a diabetic murine model (streptozotocin-induced C57BL/6J), co-implantation of human islets with IL-10-producing cells attenuated pericapsular fibrosis, preserved islet viability, and restored normoglycemia for up to 100 days (4.76 times longer than islets alone). Significantly, IL-10-producing cells were also effective in enabling the durability and function of encapsulated cells in a healthy non-human primate, showing translational feasibility. Collectively, these findings suggest that localized cytokine delivery can reduce fibrotic encapsulation and support durable graft function, offering a path to lessen reliance on systemic immunosuppression in islets transplantation and other implantable biomaterial therapies. TeaserEncapsulated IL-10-producing cells locally suppress fibrosis and extend graft function in rodent models and a non-human primate.

bioengineering↗

bioRxiv2025

What drives cultural ecosystem services in mountain protected areas? An AI-assisted answer using social media

High mountain protected areas (PAs) are increasingly recognized not only for their role in conserving biodiversity but also for their contribution to the provision of cultural ecosystem services (CES). Despite their relevance, CES remain underrepresented in conservation planning, particularly due to challenges in quantifying their spatial distribution. This study combines geolocated social media data and ecological niche models (ENMs) to assess the spatial patterns and key drivers of CES supply across eight mountain PAs spanning distinct biogeographical regions in Spain and Portugal. Using deep learning techniques to classify more than 200,000 photographs into ten CES categories, we evaluated model performance under two modeling approaches and identified the most influential environmental and social predictors. Most CES categories exhibited good model performance (Boyce index > 0.5), though variation existed across services and regions. Nature & Landscape and Gastronomy CES showed strong associations with park boundaries and human settlements, respectively, while Religious and Cultural CES were spatially linked to culturally significant landmarks.. Our findings demonstrate the potential of combining social media data with ENMs to map CES distributions and reveal both universal and context-dependent drivers. This approach offers valuable insights for integrating CES into PA management and spatial planning, supporting more holistic and culturally inclusive conservation strategies.

ecology↗

bioRxiv2025

iSleep: Continuous, binocular pupil tracking in sleep and reduced consciousness for physiological monitoring, predictions and interventions

Monitoring pupil dynamics is a key tool in understanding arousal. Pupil size can serve as a biomarker for the autonomic nervous system balance as well as for identifying brain states. While internal states can also be self-reported when awake, automated detection and non-invasive monitoring is crucial during sleep and reduced consciousness. Here, we introduce iSleep, an innovative pupil tracking and analysis framework for sleep in humans. It features comfortable, humidified eye-tracking goggles and a platform for integrated analysis and prediction capabilities. We show that iSleep allows safe and continuous access to binocular pupil size and ocular dynamics during sleep and anesthesia. iSleep reveals that pupillary fluctuations correlate tightly with brain activity, heartbeat, and breathing, and can reliably predict brain states. Pupil constrictions reflect parasympathetic drive and likely serve a protective function for deep sleep stability; while dilations indicate arousals. Unexpectedly, we observed a decoupling of binocular movements during periods of sleep, indicating alterations in reflexes which usually govern voluntary eye movements. Finally, iSleep was tested in surgery patients under general anesthesia, revealing dynamic pupil changes to noxious stimuli, suggesting the potential for nociception monitoring during surgeries. In summary, iSleep offers an easy-to-use, robust alternative to read out brain states during sleep and anesthesia, opening new avenues in monitoring, diagnostics, and treatments, previously obscured by closed eyelids.

neuroscience↗

bioRxiv2025

Intercellular signaling stabilizes single-cell level phenotypic transitions and accelerates the reestablishment of equilibrium of heterogeneous cancer cell populations

BackgroundCancer cells within tumors exhibit a wide range of phenotypic states driven by non-genetic mechanisms in addition to extensively studied genetic alterations. Conversions among cancer cell states can result in intratumoral heterogeneity which contributes to metastasis and development of drug resistance. However, mechanisms underlying the initiation and/or maintenance of such phenotypic plasticity are poorly understood. In particular, the role of intercellular communications in phenotypic plasticity remains elusive. MethodsIn this study, we employ a multiscale inference-based approach using single-cell RNA sequencing (scRNA-seq) data to explore how intercellular interactions influence phenotypic dynamics of cancer cells, particularly cancers undergoing epithelial-mesenchymal transition. In addition, we use mathematical models based on our data-driven findings to interrogate the roles of intercellular communications at the cell populations from the viewpoint of dynamical systems. ResultsOur inference approach reveals that signaling interactions between cancerous cells in small cell lung cancer (SCLC) result in the reinforcement of the phenotypic transition in single cells and the maintenance of population-level intratumoral heterogeneity. Additionally, we find a recurring signaling pattern across multiple types of cancer in which the mesenchymal-like subtypes utilize signals from other subtypes to support its new phenotype, further promoting the intratumoral heterogeneity. Our models show that inter-subtype communication both accelerates the development of heterogeneous tumor populations and confers robustness to their steady state phenotypic compositions. ConclusionsOur work highlights the critical role of intercellular signaling in sustaining intratumoral heterogeneity, and our approach of computational analysis of scRNA-seq data can infer inter- and intra-cellular signaling networks in a holistic manner.

systems biology↗

bioRxiv2024

A critical affinity window for IgSF proteins DIP-α and Dpr10 is required for proper motor neuron arborization

For flies to walk properly, motor neurons (MNs) from the ventral nerve cord (VNC) need to reach the correct muscle, and arborize appropriately during development. The canonical view of how this is achieved is that cell surface proteins are expressed pre- and post-synaptically that bind to each other like molecular "lock-and-keys" that guide neurons to their targets. The binding affinities of these molecules can vary by more than 100-fold. In the fly leg neuromuscular system, three MNs express DIP- and their target muscles express its cognate partner, dpr10, both of which encode members of the Immunoglobulin superfamily (IgSF). Although, both of these molecules are necessary for the maintenance of MN-muscle contacts, the role that specific affinities play in this process has not been examined. Here we use knock-in mutations into DIP- and dpr10 that either decrease or increase the affinity between these two proteins. Compared to control animals, decreasing the affinity results in phenotypes similar to DIP- or dpr10 null animals, where MN axons fail to maintain contacts with their muscle targets and retract their filopodia, resulting in stunted and/or branchless axons. We also find that the three DIP--expressing motor neurons behave differently to the loss of affinity. Surprisingly, if the affinity increases past a certain threshold, a similar branchless phenotype is observed in adult legs. Live imaging during pupal development shows that MN filopodia are unable to productively engage their muscle targets and behavioral assays suggest that these defects lead to locomotor deficits. These data suggest that CAM affinities are tuned to a specific range to achieve proper neuronal morphology.

developmental biology↗

bioRxiv2024

Spatiotemporal dispersion of DENV1 genotype V in western Colombia

Dengue virus (DENV) is a significant public health concern in Colombia, with increased transmission of DENV type 1 (DENV-1) in the departments of Risaralda and Valle del Cauca in the Central-West region of the country following a large outbreak in 2019. However, little is known about the source, genetic diversity, and evolution of circulating viruses. We obtained plasma samples from individuals with acute DENV infection and analyzed DENV-1 genetic diversity, phylodynamics, and phylogeography. We found that most viruses belonged to DENV-1 genotype V, and phylogenetic analysis revealed three distinct clades, each of which was most closely related to viruses from neighboring departments of Colombia sampled over the last 5-10 years. Thus, the 2019 outbreak and subsequent DENV-1 circulation was not due to the introduction of a new lineage but rather reflected local DENV-1V dispersion and evolution. We identified amino acid positions under positive selection in structural proteins and NS1, which may have a role in immune evasion and pathogenesis. Overall, our analysis of DENV1 genotype V diversity, evolution and spread within Colombia highlights the important role of genomic surveillance in understanding virus dynamics during endemic circulation and outbreaks.

evolutionary biology↗

bioRxiv2023

Phase-changing citrate macromolecule combats oxidative pancreatic islet damage, enables islet engraftment and function in the omentum

Clinical outcomes for total-pancreatectomy followed by intraportal islet autotransplantation (TP-IAT) to treat chronic pancreatitis (CP) patients are suboptimal due to the inflammatory state of the patients pancreas, oxidative tissue damage during the isolation process, and the harsh engraftment conditions in the livers vasculature, which include ischemia-reperfusion injury, and instant blood-mediated inflammatory reactions. We describe the use of the thermoresponsive, antioxidant macromolecule poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) to protect islet redox status and function in vitro and in vivo and to create a viable extrahepatic islet engraftment site in the abdomen. PPCN in aqueous media transitions from a liquid to an elastic hydrogel when exposed to body temperature via temperature-induced macromolecular self-assembly. Islets entrapped in the PPCN hydrogel and exposed to oxidative stress remain functional and support long-term euglycemia, in contrast to islets entrapped in a biologic scaffold (BS). When applied to the omentum of non-human primates (NHPs), PPCN is well-tolerated, safe, and mostly resorbed without fibrosis at 3 months post-implantation. To obtain autologous islets, a partial pancreatectomy was performed, followed by STZ administration to induce diabetes and destroy any remaining endogenous islets. Application of the autologous islets to the momentum using PPCN restored normoglycemia with minimal insulin requirements for over 100 days. These results support the use of PPCN as a scaffold for minimally invasive delivery of islets to the omentum of pancreatitis patients and highlight the importance of scaffold antioxidant properties as a new mechanism to protect islet function and maximize long-term autologous graft performance. One Sentence SummaryOmentum islet transplantation using a thermoresponsive, antioxidative polymer supports autologous islet viability and function in nonhuman primates.

bioengineering↗

bioRxiv2023

Pan-viral ORFs discovery using Massively Parallel Ribosome Profiling

Unveiling the complete proteome of viruses is crucial to our understanding of the viral life cycle and interaction with the host. We developed Massively Parallel Ribosome Profiling (MPRP) to experimentally determine open reading frames (ORFs) in 20,170 designed oligonucleotides across 679 human-associated viral genomes. We identified 5,381 ORFs, including 4,208 non-canonical ORFs, and show successful detection of both annotated coding sequences (CDSs) and reported non-canonical ORFs. By examining immunopeptidome datasets of infected cells, we found class I human leukocyte antigen (HLA-I) peptides originating from non-canonical ORFs identified through MPRP. By inspecting ribosome occupancies on the 5UTR and CDS regions of annotated viral genes, we identified hundreds of upstream ORFs (uORFs) that negatively regulate the synthesis of canonical viral proteins. The unprecedented source of viral ORFs across a wide range of viral families, including highly pathogenic viruses, expands the repertoire of vaccine targets and exposes new cis-regulatory sequences in viral genomes.

systems biology↗

bioRxiv2023

Functional membrane microdomains and the hydroxamate siderophore transporter ATPase FhuC govern Isd-dependent heme acquisition in Staphylococcus aureus

Sufficient access to transition metals such as iron is essential for bacterial proliferation and their active limitation within host tissues effectively restricts infection. To overcome iron limitation, the invasive pathogen Staphylococcus aureus uses the iron-regulated surface determinant (Isd) system to acquire hemoglobin-derived heme. While heme transport over the cell wall is well understood, its transport over the membrane is hardly investigated. In this study, we show the heme-specific permease IsdF to be energized by the general ATPase FhuC. Additionally, we show that IsdF needs appropriate location within the membrane for functionality. The membrane of S. aureus possesses special compartments (functional membrane microdomains - FMMs) to organize membrane complexes. We show IsdF to be associated with FMMs, to directly interact with the FMM scaffolding protein flotillin A (FloA) and to co-localize with the latter on intact bacterial cells. Additionally, Isd-dependent bacterial growth required FMMs and FloA. Our study shows that Isd-dependent heme acquisition requires a highly structured cell envelope to allow coordinated transport over the cell wall and membrane and it gives the first example of a bacterial nutrient acquisition system that depends on FMMs.

microbiology↗

bioRxiv2022

Escherichia coli membrane microdomain SPFH protein HflC interacts with YajC and contributes to aminoglycoside and oxidative stress tolerance

Many eukaryotic membrane-dependent functions are often spatially and temporally regulated by membrane microdomains (FMMs) also known as lipid rafts. These domains are enriched in polyisoprenoid lipids and scaffolding proteins belonging to the Stomatin, Prohibitin, Flotillin, and HflK/C (SPFH) protein superfamily that was also identified in Gram-positive bacteria. By contrast, little is still known about FMMs in Gram-negative bacteria. In Escherichia coli K12, 4 SPFH proteins, YqiK, QmcA, HflK, and HflC, were shown to localize in discrete polar or lateral inner-membrane locations, raising the possibility that E. coli SPFH proteins could contribute to the assembly of inner-membrane FMMs and the regulation of cellular processes. Here we studied the determinant of the localization of QmcA and HflC and showed that FMM-associated cardiolipin lipid biosynthesis is required for their native localization pattern. Using Biolog phenotypic arrays, we showed that a mutant lacking all SPFH genes displayed increased sensitivity to aminoglycosides and oxidative stress that is due to the absence of HflKC. Our study therefore provides further insights into the contribution of SPFH proteins to stress tolerance in E. coli. IMPORTANCEEukaryotic cells often segregate physiological processes in cholesterol-rich functional membrane micro-domains. These domains are also called lipid rafts and contain proteins of the Stomatin, Prohibitin, Flotillin, and HflK/C (SPFH) superfamily, which are also present in prokaryotes but were mostly studied in Gram-positive bacteria. Here, we showed that the cell localization of the SPFH proteins QmcA and HflKC in the Gram-negative bacteria E. coli is altered in absence of cardiolipin lipid synthesis. This suggests that cardiolipins contribute to E. coli membrane microdomain assembly. Using a broad phenotypic analysis, we also showed that HflKC contribute to E. coli tolerance to aminoglycosides and oxidative stress. Our study, therefore, provides new insights into the cellular processes associated with SPFH proteins in E. coli.

microbiology↗

bioRxiv2021

Mites alight! Sunflower crop area and pollen supplementation enhance honey bee resistance to Varroa destructor

Anthropogenic landscape changes can affect parasite epidemiology in wild and agricultural animals. Honey bees are agricultural animals whose services are threatened by loss of floral resources and by parasites, most notably the invasive mite Varroa destructor. Existing mite control strategies rely heavily on chemical treatments that can adversely affect bees. Alternative, pesticide-free control methods are urgently needed to maintain effective pollination services. Many flowering plants provide nectar and pollen that enhance resistance to parasites in animals. Enrichment of landscapes with antiparasitic floral resources could therefore provide a sustainable means of parasite control in pollinators. Floral rewards of Asteraceae plants have been shown to reduce parasitic infection in diverse bee species, including honey and bumble bees. Here, we tested the effects of sunflower (Helianthus annuus) cropland and pollen supplementation on honey bee resistance to macro- and microparasites. Our results show that each doubling of sunflower crop area is associated with a 28% reduction in mite infestation intensity. Late-summer supplementation of colonies with sunflower pollen reduced mite infestation by 2.75-fold relative to an artificial pollen. Our findings suggest the potential for sunflower plantings or pollen supplements to counteract a main driver of honey bee losses worldwide.

ecology↗

bioRxiv2021

Predicted Impact of the Viral Mutational Landscape on the Cytotoxic Response against SARS-CoV-2

The massive assessment of immune evasion due to viral mutations that potentially increase COVID-19 susceptibility can be computationally facilitated. The adaptive cytotoxic T response is critical during primary infection and the generation of long-term protection. Potential epitopes in the SARS-CoV-2 proteome were predicted for 2,915 human alleles of 71 HLA class I families. Allele families showed extreme differences in number of recognized epitopes, underscoring genetic variability of protective capacity between humans. Up to 1,222 epitopes were associated with any of the twelve supertypes, that is, allele clusters covering 90% population. Among them, the B27 supertype showed the lowest number of epitopes. Epitope escape mutations identified in ~118,000 NCBI isolates mainly involved non-conservative substitutions at the second and C-terminal position of the ligand core, or total ligand removal by large recurrent deletions. Escape mutations affected 47% of supertype epitopes, which in 21% of cases concerned isolates from two or more sub-continental areas. Some of these changes were coupled, but never surpassed 15% evaded epitopes for the same supertype in the same isolate, except for B27, which reached up to 33%. In contrast to most supertypes, eight particular allele families mostly contained alleles with few SARS-CoV-2 ligands. Isolates harboring cytotoxic escape mutations for these families co-existed geographically within sub-Saharan and Asian populations enriched in these alleles. Collectively, these data indicate that independent escape mutation events have already occurred for half of HLA class I supertype epitopes. However, it is presently unlikely that, overall, it poses a threat to the global population. In contrast, single and double mutations for susceptible alleles may be associated with viral selective pressure and alarming local outbreaks. This study highlights the automated integration of genomic, geographical and immunoinformatic information for surveillance of SARS-CoV-2 variants potentially affecting the population as a whole, as well as minority subpopulations. AUTHOR SUMMARYThe cytotoxic T response, a type of immune response dependent upon an individual's genetics that does not require antibodies, is critical for neutralizing SARS-CoV-2 infection. The potential bypass of the cytotoxic T response by mutations acquired by the virus after one year of the pandemic is therefore of maximal concern. We have approached the complexity of human variability and more than 100.000 viral genomes in this respect using a computational strategy. We have detected numerous mutations in these genomes that mask some viral regions involved in the cytotoxic response. However, the accumulation of these changes in independent isolates is still too low to threaten the global human population. In contrast, our protocol has identified mutations that may be relevant for specific populations and minorities with cytotoxic genetic backgrounds susceptible to SARS-CoV-2 infection. Some viral variants co-existed in the same country with these human communities which warrants deeper surveillance in these cases to prevent local outbreaks. Our study support the integration of massive data of different natures in the surveillance of viral pandemics.

immunology↗

bioRxiv2020

The Bacterial Cytoskeleton Spatially Confines Functional Membrane Microdomains

Cell membranes laterally segregate into microdomains enriched in certain lipids and scaffold proteins. Membrane microdomains modulate protein-protein interactions and are essential for cell polarity, signaling and membrane trafficking. How cells organize their membrane microdomains, and the physiological importance of these microdomains, is unknown. In eukaryotes, the cortical actin cytoskeleton is proposed to act like a fence, constraining the dynamics of membrane microdomains. Like their eukaryotic counterparts, bacterial cells have functional membrane microdomains (FMMs) that act as platforms for the efficient oligomerization of protein complexes. In this work, we used the model organism Bacillus subtilis to demonstrate that FMM organization and movement depend primarily on the interaction of FMM scaffold proteins with the domains protein cargo, rather than with domain lipids. Additionally, the MreB actin-like cytoskeletal network that underlies the bacterial membrane was found to frame areas of the membrane in which FMM mobility is concentrated. Variations in membrane fluidity did not affect FMM mobility whereas alterations in cell wall organization affected FMM mobility substantially. Interference with MreB organization alleviates FMM spatial confinement whereas, by contrast, inhibition of cell wall synthesis strengthens FMM confinement. The restriction of FMM lateral mobility by the submembranous actin-like cytoskeleton or the extracellular wall cytoskeleton appears to be a conserved mechanism in prokaryotic and eukaryotic cells for localizing functional protein complexes in specific membrane regions, thus contributing to the organization of cellular processes.

microbiology↗

bioRxiv2019

Aberrant cocoons found on honey bee comb cells are found to be Osmia cornifrons (Radoszkowski) (Hymenoptera Megachilidae)

Potential biological threats to honey bees must be addressed and validated quickly, before making disruptive and costly decisions. Here we describe numerous Osmia cornifrons (Hymenoptera: Megachilidae) cocoons in honey bee cells from one bee hive in Ohio. The developing Osmia cells presented themselves as a mystery at first, catching the attention of regulatory agencies. Along with identifying this species as a presumably benign resident in honey bee colonies, our observations suggest Osmia may use stored honey bee resources to provision offspring. Conceivably, resident honey bees might even act as surrogates, by provisioning Osmia offspring with pollen. Since the cocoons were attached to one another with honey bee wax, it seems likely that honey bee hosts were present during Osmia development. Osmia females have some plasticity when selecting nesting resources, and, upon discovering honey bee comb can use this resource for raising offspring. Along with resolving a potentially new biotic threat to honey bees, this diagnosis suggests a method for mass production of Osmia pollinators using an array of single cell foundation.

zoology↗

bioRxiv2019

Effects of initial microbial biomass abundance on respiration during pine litter decomposition

Microbial biomass is increasingly used to predict respiration in soil organic carbon (SOC) models. Its increased use combined with the difficulty of accurately measuring this variable points a need to directly assess the importance of microbial biomass abundance for carbon (C) cycling. To test the hypothesis that the initial microbial biomass abundance (i.e. biomass abundance on new plant litter) is a strong driver of plant litter C cycling, we manipulated biomass abundance by 10 and 100-fold dilution and composition using 12 source communities on sterile pine litter and measured respiration in microcosms for 30 days. In the first two days of microbial growth on fresh litter, a 100-fold difference in initial biomass abundance caused an average difference in respiration of nearly 300%, but the effect rapidly declined to less than 30% in 10 days and to 14% in 30 days. Parallel simulations with a soil carbon model, SOMIC 1.0, also predicted a 14% difference over 30 days, consistent with the experimental results. Model simulations predicted convergence of cumulative CO2 to within 10% in three months and within 4% in three years. Rapid microbial growth likely attenuates the effects of large initial differences in biomass abundance. In contrast, the persistence of source community as an explanatory factor in driving differences in respiration across microcosms supports the importance of microbial composition in C cycling. Overall, the results suggest that the initial abundance of microbial biomass on litter is a weak driver of C flux from litter decomposition over long timescales (months to years) when litter communities have equal nutrient availability. By extension, slight variation in the timing of microbial dispersal to fresh litter is likely to be a minor factor in long-term C flux.\n\nImportanceMicrobial biomass is one of the most common microbial parameters used in land carbon (C) cycle models, however, it is notoriously difficult to measure accurately. To understand the consequences of mismeasurement, as well as the broader importance of microbial biomass abundance as a direct driver of ecological phenomena, greater quantitative understanding of the role of microbial biomass abundance in environmental processes is needed. Using microcosms, we manipulated the initial biomass of numerous microbial communities across a 100-fold range and measured effects on CO2 production during plant litter decomposition. We found that the effects of initial biomass abundance on CO2 production was largely attenuated within a week, while the effects of community type remained significant over the course of the experiment. Overall, our results suggest that initial microbial biomass abundance in litter decomposition within an ecosystem is a weak driver of long-term C cycling dynamics.

microbiology↗