Biology subjects

Booth, R.

Publications and source records attributed to Booth, R..

6 recordsLinked to original sources

bioRxiv2025

Dynamic and Catalytic Multiphase Coacervates

Subcellular organization is critical for myriad cellular functions, including spatiotemporal regulation of biocatalysts. Liquid-liquid phase separation contributes to intracellular organization by providing microenvironments that sequester biomolecules and control their activities. Although catalytic reactions in multiphase coacervate systems are important for living cells, provide functionality to artificial systems, and may aid understanding of how metabolism first arose, they are not well understood. Here we report an artificial multiphase system in which catalytically active droplets containing three distinct coexisting coacervate phases undergo reorganization in response to pH, enabling control over chemical reactions. Catalysis is performed by an inner, polyhistidine-dense coacervate phase with inherent nonenzymatic activity. We show how phase composition, in addition to pH, affects catalytic activity, and how the addition of enzymes that alter local pH provides a means to regulate composition and catalysis. By exploiting competitive interplay between intramolecular self-association and intermolecular complexation among polymers within multiphase coacervate systems, it was possible to (re)organize and tune the reactivity of dynamic synthetic biological systems beyond what is possible for single-phase coacervates. Such approaches could prove valuable in designing artificial cells and related microreactor systems capable of catalyzing and controlling complex chemical and biochemical processes.

biochemistry↗

bioRxiv2024

Hybrid Protocells based on Coacervate-Templated Fatty Acid Vesicles combine Improved Membrane Stability with Functional Interior Protocytoplasm

Prebiotically-plausible compartmentalization mechanisms include membrane vesicles formed by amphiphile self-assembly and coacervate droplets formed by liquid-liquid phase separation. Both types of structures form spontaneously and can be related to cellular compartmentalization motifs in todays living cells. As prebiotic compartments, they have complementary capabilities, with coacervates offering excellent solute accumulation and membranes providing superior boundaries. Herein, we describe protocell models constructed by spontaneous encapsulation of coacervate droplets by mixed fatty acid/phospholipid and by purely fatty acid membranes. Coacervate-supported membranes formed over a range of coacervate and lipid compositions, with membrane properties impacted by charge-charge interactions between coacervates and membranes. Vesicles formed by coacervate-templated membrane assembly exhibited profoundly different permeability than traditional fatty acid or blended fatty acid/phospholipid membranes without coacervate interiors, particularly in the presence of Mg2+ ions. While fatty acid and blended membrane vesicles were disrupted by addition of 25 mM MgCl2, the corresponding coacervate-supported membranes remained intact and impermeable to externally-added solutes even in the presence of MgCl2. With the more robust membrane, fluorescein diacetate (FDA) hydrolysis, which is commonly used for cell viability assays, could be performed inside the protocell model due to the simple diffusion of FDA and then following with the coacervate-mediated abiotic hydrolysis to fluorescein.

biophysics↗

bioRxiv2023

Oxycodone self-administration and reinstatement in male and female squirrel monkeys: Effects of alternative reinforcer availability

The use of non-drug alternative reinforcers has long been utilized as a component of therapeutic interventions for the management of substance use disorder; however, the conditions under which alternative reinforcers are most effective are not well characterized. This study evaluated the impact of varying the magnitude of an alternative reinforcer on oxycodone self-administration and reinstatement in male and female squirrel monkeys. Subjects (n=4/sex) were trained under concurrent second-order schedules of reinforcement for intravenous oxycodone (0.001-0.1mg/kg/inj) on one lever, and sweetened condensed milk (5, 10, 20, 30% in water) on another. Oxycodone-primed reinstatement was evaluated by administering 0.32mg/kg oxycodone prior to sessions in which saline was available on the drug-paired lever. During oxycodone self-administration sessions, milk availability decreased oxycodone self-administration and preference in a concentration-dependent manner; low milk concentrations were more effective at decreasing oxycodones reinforcing potency in males. During reinstatement tests, milk significantly attenuated oxycodone-primed responding in both males and females; low milk concentrations were more effective at decreasing the priming effects of oxycodone in females. That alternative reinforcers differentially impacted self-administration and reinstatement in a sex-dependent manner suggests that treatment strategies that utilize alternative reinforcers may be more effective in males or females depending on when they are implemented.

pharmacology and toxicology↗

bioRxiv2019

A periplasmic L,D-carboxypeptidase is important for cell morphology, membrane integrity, and virulence in Francisella tularensis

Francisella tularensis is a Gram-negative, intracellular bacterium that causes the zoonotic disease tularemia. Intracellular pathogens, including F. tularensis, have evolved mechanisms to survive in the harsh environment of macrophages and neutrophils, where they are exposed to cell envelope-damaging molecules. The bacterial cell wall, primarily composed of peptidoglycan (PG), maintains cell morphology, structure, and membrane integrity. Intracellular Gram-negative bacteria protect themselves from macrophage and neutrophil killing by recycling and repairing damaged PG - a process that involves over 50 different PG synthesis and recycling enzymes. Here, we identified a PG recycling enzyme, L,D-carboxypeptidase A (LdcA), of F. tularensis that is responsible for converting PG tetrapeptide stems to tripeptide stems. Unlike E. coli LdcA and most other orthologs, F. tularensis LdcA does not localize to the cytoplasm and also exhibits L,D-endopeptidase activity, converting PG pentapeptide stems to tripeptide stems. Loss of F. tularensis LdcA led to altered cell morphology and membrane integrity, as well as attenuation in a mouse pulmonary infection model and in primary and immortalized macrophages. Finally, an F. tularensis ldcA mutant protected mice against virulent Type A F. tularensis SchuS4 pulmonary challenge.

microbiology↗

bioRxiv2018

Climate or disturbance: temperate forest structural change and carbon sink potential

Anticipating forest responses to changing climate and disturbance regimes requires understanding long-term successional processes and aggregating these local processes into global relevance. Estimates of existing forest structure and biomass are improving globally; however, vegetation models continue to show substantial spread in predictions of future land carbon uptake and the roles of forest structural change and demography are increasingly being recognized as important. To identify mechanisms that drive change in tree size, density, and carbon, we need a better understanding of forest structural trajectories and the factors that affect those trajectories. Here we reveal a coherent, cyclic pattern of structural change in temperate forests, as predicted by successional theory, and identify significant sensitivity to climatic precipitation and temperature anomalies using large datasets and empirical modeling. For example, in the eastern US above average temperature (+1{degrees}C) was associated with a 27% (-0.4{+/-}0.1 Mg C ha-1 yr-1) reduction in productivity attributed to higher rates of disease (+23%), weather disturbance (+57%), and sapling mortality. Projections of future vegetative carbon sink potential suggests biomass would be lowest on managed lands (72{+/-}2 Mg C ha-1) and highest when larger trees survive in undisturbed conditions (153{+/-}21 Mg C ha-1). Overall, the indirect effects of disturbance and mortality were considerably larger than the direct effects of climate on productivity when predicting future vegetative carbon sinks. Results provide robust comparisons for global vegetation models, and valuable projections for management and carbon mitigation efforts.

ecology↗

bioRxiv2018

The impact of human activities on Australian wildlife

Increasing human population size and the concomitant expansion of urbanisation significantly impact natural ecosystems and native fauna globally. Successful conservation management relies on precise information on the factors associated with wildlife population decline, which are challenging to acquire from natural populations. Wildlife Rehabilitation Centres (WRC) provide a rich source of this information. However, few researchers have conducted large-scale longitudinal studies, with most focussing on narrow taxonomic ranges, suggesting that WRC-associated data remains an underutilised resource, and may provide a fuller understanding of the anthropogenic threats facing native fauna.\n\nWe analysed admissions and outcomes data from a WRC in Queensland, Australia Zoo Wildlife Hospital, to determine the major factors driving admissions and morbidity of native animals in a region experiencing rapid and prolonged urban expansion.\n\nWe studied 31,626 admissions of 83 different species of native birds, reptiles, amphibians, marsupials and eutherian mammals from 2006 to 2017. While marsupial admissions were highest (41.3%), admissions increased over time for all species and exhibited seasonal variation (highest in Spring to Summer), consistent with known breeding seasons.\n\nCauses for admission typically associated with human influenced activities were dominant and exhibited the highest mortality rates. Car strikes were the most common reason for admission (34.7%), with dog attacks (9.2%), entanglements (7.2%), and cat attacks (5.3% also high. Admissions of orphaned young and overt signs of disease were significant at 24.6% and 9.7%, respectively. Mortality rates were highest following dog attacks (72.7%) and car strikes (69.1%) and lowest in orphaned animals (22.1%).\n\nOur results show that WRC databases offer rich opportunities for wildlife monitoring and provide quantification of the negative impacts of human activities on ecosystem stability and wildlife health. The imminent need for urgent, proactive conservation management to ameliorate the negative impacts of human activities on wildlife is clearly evident from our results.

ecology↗