Biology subjects

Campbell, G.

Publications and source records attributed to Campbell, G..

8 recordsLinked to original sources

bioRxiv2024

Detection of airborne Coccidioides spores using lightweight portable air samplers affixed to uncrewed aircraft systems in California's Central Valley

Coccidioidomycosis is an emerging fungal infection caused by inhalation of Coccidioides spp. spores. While airborne dispersal is critical to Coccidioides transmission, limited recovery of the pathogen from air has hindered understanding of the aerosolization and transport of spores. Here, we examine uncrewed aircraft systems (UAS) with portable, active air samplers as a novel means of capturing aerosolized Coccidioides and characterizing emissions and exposure risk. We sampled in September 2023 in eastern San Luis Obispo County, California, in an area with confirmed Coccidioides immitis in soils. We completed 41 20-minute flights across 14 sites using UAS equipped with an 8 L/min bioaerosol sampler and a low-cost particulate matter sensor. We sampled source soils and air under ambient conditions using one UAS at 1-10 m above ground level, and under a simulated high-dust event using two UAS, one at <2 m height and one at 5-12 m. We detected Coccidioides DNA in two of 41 air samples (4.9%), both under ambient conditions at 8 m above ground level, representing the highest known height of airborne Coccidioides detection. Spatially explicit UAS-based sampling could enhance understanding of Coccidioides aerobiology and enable detection in hard-to-reach or hazardous air masses, including dust storms and wildfire smoke. SynopsisUAS-based air sampling for bioaerosols, including pathogenic Coccidioides spp., opens new possibilities for characterizing the aerosolization and transport of fungal spores and other airborne pathogens.

ecology↗

bioRxiv2024

Small mammals and their burrows shape the distribution of Coccidioides in soils: a long-term ecological experiment

BackgroundFor nearly all human fungal pathogens, the environmental constraints on their distributions remain poorly understood, hindering disease management. Here, we investigated the role of zoonotic host presence, soil conditions, and their interaction on the presence of Coccidioides immitis - an emerging fungal pathogen and causative agent of coccidioidomycosis. MethodsA long-term experimental study initiated in 2007 in the Carrizo Plain National Monument, California excluded rodents from certain areas (20 by 20-meter exclosures; n = 20) via the installation of submerged mesh fences, leaving emptied burrows intact. We collected 1,988 soil samples over four sampling periods spanning April 2021 to April 2022 using a factorial design that crossed burrows and surface soils (i.e., top 10 cm of soil) with exclosures (i.e., rodent absence) and non-exclosures (i.e., rodent presence). We measured in situ soil moisture, temperature, and vegetation, and analyzed soils for C. immitis DNA. ResultsThe proportion of samples containing C. immitis was significantly higher (p <0.0001) in burrow samples taken from outside rodent exclosures (i.e., rodents present; 28.5% positive) compared to burrow samples taken from within exclosures (i.e., rodents absent; 19.7%), surface soils outside of exclosures (3.6%) and surface soils within exclosures (0.5%). In generalized linear mixed models adjusting for soil conditions, rodent presence, and sample type (burrow vs. surface soil), we estimated that the odds of detecting C. immitis were 19.2 (95% CI: 11.3 - 36.7, p < 0.0001) times higher in soils taken from burrows compared to surface soils, and 2.6 (95% CI: 1.0 - 5.6, p = 0.049) times higher in soils where rodents were present compared to absent. Soil moisture was the only abiotic factor associated with C. immitis detection (odds ratio per 1% increase in water content: 0.83, 95% CI: 0.70 - 0.89, p = 0.0002). In mediation analyses, we estimated that 73.7% (95% CI: 68.9, 78.5) of the total association between rodents and Coccidioides detection effect was attributable to rodent creation of burrows. ConclusionsRodent creation and occupation of burrows substantially increases C. immitis detection. Synergy between reservoir host presence and environmental conditions may exist for other human fungal pathogens.

ecology↗

bioRxiv2023

Threat of mining to African great apes

The rapid growth of clean energy technologies is driving a rising demand for critical minerals. In 2022 at the UN Biodiversity Conference (COP 15), seven major economies formed an alliance to enhance the sustainability of mining these essential decarbonization minerals. However, there is a scarcity of studies assessing the threat of mining to global biodiversity. By integrating a global mining dataset with ape density distribution estimates, we explored the potential negative impact of industrial mining on African great apes. Our findings reveal that up to one-third of Africas great ape population faces mining-related risks. This is especially pronounced in West Africa, where numerous mining areas overlap with fragmented ape habitats, often occurring in high-density ape regions. For 97% of mining areas, no ape survey data are available, underscoring the importance of increased accessibility to environmental data within the mining sector to facilitate research into the complex interactions between mining, climate, biodiversity and sustainability. TeaserMining for clean energy minerals could put one-third of Africas ape population at risk.

ecology↗

bioRxiv2022

The two-component system CroRS regulates isoprenoid flux to mediate antimicrobial tolerance in the bacterial pathogen Enterococcus faecalis

Antimicrobial tolerance is the ability of a microbial population to survive, but not proliferate, during antimicrobial exposure. Significantly, it has been shown to precede the development of bona fide antimicrobial resistance. We have previously identified the two-component system CroRS as a critical regulator of tolerance to antimicrobials like teixobactin in the bacterial pathogen Enterococcus faecalis. To understand the molecular mechanism of this tolerance, we carried out RNA-seq analyses in the E. faecalis wild-type and isogenic {Delta}croRS mutant to determine the teixobactin-induced CroRS regulon. We identified a 132 gene CroRS regulon and show CroRS upregulates expression of all major components of the enterococcal cell envelope in response to teixobactin challenge. To gain further insight into the function of this regulon we isolated and characterized {Delta}croRS mutants recovered for wild-type growth and tolerance. We show introduction of a single stop codon in a heptaprenyl diphosphate synthase (hppS), a key enzyme in the synthesis of the quinone electron carrier demethylmenaquinone (DMK), is sufficient to rescue loss of cell envelope integrity in the croRS deletion strain. Based on these findings, we propose a model where CroRS acts as a gate-keeper of isoprenoid biosynthesis, mediating flux of isoprenoids needed for cell wall synthesis (undecaprenyl pyrophosphate; UPP) and respiration (DMK) to maintain cell wall homeostasis upon antimicrobial challenge. Dysregulation of this flux in the absence of croRS leads to a loss of tolerance, which is rescued by loss of function mutations in HppS, allowing an increase in isoprenoid flow to UPP and subsequently cell wall synthesis. ImportanceAntimicrobial tolerance is the ability of a microorganism to survive, but not grow upon antimicrobial challenge, and is an important precursor to the development of antimicrobial resistance (the ability to profilerate). Understanding the molecular mechanisms that underpin tolerance will therefore aid in hampering the development of resistance to novel antimicrobials such as teixobactin. CroRS is an essential two-component regulator of antimicrobial tolerance in the bacterial pathogen Enterococcus faecalis. We have determined the antimicrobial-induced CroRS regulon and identified key mutations in a heptaprenyl diphosphate synthase to uncover a novel mechanism of antimicrobial tolerance.

microbiology↗

bioRxiv2022

Cell walls are dynamically O-acetylated in the green seaweed, Ulva compressa

We report that cell wall polymers in the chlorophyte algae may be modified by O-acetylation. The importance of cell wall modifications in the green algae is not well understood, although similar modifications play key roles in land plants by modulating the properties of cell wall carbohydrate polymers. Using a combination of biophysical (Fourier-transform infrared and cross-polarisation heteronuclear correlation nuclear magnetic resonance spectroscopy), biochemical (thin-layer chromatography) and molecular approaches (yellow fluorescent protein-tagged transgene localisation), we show that the extractable ulvan fractions of Ulva compressa cell walls contain O-acetyl sidechains, we demonstrate that acetylation is dynamic and decreases reversibly in response to metal-induced stress, we note interactions between acetyl and borate sidechains and we locate two candidate genes that, together, may encode an acetyltransferase. We therefore propose that O-acetylation of ulvan residues is involved in the normal cell wall physiology of at least some chlorophyte algae. To the best of our knowledge, this is the first demonstration of O-acetyl sidechains in green algal cell wall polymers, and of reversible changes in algal cell wall polymer modification in response to stress.

cell biology↗

bioRxiv2020

Myelinating Schwann cells use Warburg effect to sustain axonal physiology and function

Despite the lactate shuttle theory, how glial cells support axonal metabolism and function remains unclear. Lactate production is a common occurrence following anaerobic glycolysis in muscles. However, several other cell types, including some stem cells, activatezd macrophages and tumor cells, can produce lactate in presence of oxygen and cellular respiration, using Pyruvate Kinase 2 (PKM2) to divert pyruvate to lactate dehydrogenase. We show here that PKM2 is also upregulated in mature myelinating Schwann cells (mSC) of mouse sciatic nerve. Deletion of this isoform in PLP-expressing cells in mice leads to a deficit of lactate in mSC and in peripheral nerves. This had no detectable consequences on the myelin sheath. However, mutant mice developed a peripheral neuropathy. Peripheral nerve axons of mutant mice failed to maintain lactate homeostasis upon activity, resulting in an impaired production of mitochondrial ATP. Action potential propagation was not altered but axonal mitochondria transport was slowed down, muscle axon terminals retracted and motor neurons displayed cellular stress. Additional reduction of lactate availability through dichloroacetate treatment, which diverts pyruvate to mitochondrial oxidative phosphorylation, further aggravated motor dysfunction in mutant mice. Thus, lactate production through aerobic glycolysis is essential in mSC for the long-term maintenance of peripheral nerve axon physiology and function.

neuroscience↗

bioRxiv2020

Long term AAV2/9-mediated silencing of PMP22 prevents CMT1A disease in rats and validates skin biomarkers as treatment outcome measure

Charcot-Marie-Tooth disease 1A (CMT1A) results from a duplication of the PMP22 gene leading to an excess of PMP22, a deficit of myelination and an instability of the myelin sheath in peripheral nerves. Patients present with reduced nerve conduction velocity, muscle waste, hand and foot deformations and foot drop walking problems. As gene silencing therapy has been shown to be effective in other monogenic neurological disorders, we evaluated the safety and efficacy of recombinant adeno-associated viral vector serotype 9 (AAV2/9)-based gene therapy for CMT1A. AAV2/9-mediated delivery of eGFP and shRNAs targeting PMP22 mRNA in the sciatic nerve allowed widespread gene expression in myelinating Schwann cells in mouse, rat and nonhuman primate. The treatment restored wild-type PMP22 level, increased myelination and prevented motor and sensory impairment over 12 months in a rat model of CMT1A. Intra-nerve injection limited off-target transduction and immune response to barely detectable levels. A combination of previously characterized human skin biomarkers successfully discriminated treated animals from their untreated littermate controls indicating their potential use as part of outcome measures in future clinical trials. Our results support intra nerve injection of AAV2/9 as an effective strategy for the treatment of CMT1A as well as other demyelinating CMT diseases.

neuroscience↗

bioRxiv2018

Activity-dependent production of ATP and ROS in mitochondria of myelinated axons in healthy and neuropathic conditions

Mitochondria are critical for the function and maintenance of myelinated axons notably through ATP production. A by-product of this activity is reactive oxygen species (ROS), which are highly deleterious for neurons. While ROS and metabolism are involved in several neurodegenerative diseases, it is still unclear how axonal activity or myelin modulates ATP and ROS production in axonal mitochondria. We imaged and quantified mitochondrial ATP and hydrogen peroxide (H2O2) in resting or stimulated peripheral nerve myelinated axons in vivo, using genetically-encoded fluorescent probes, two-photon time-lapse and CARS imaging. ATP and H2O2 productions are intrinsically higher in nodes of Ranvier even in resting conditions. Axonal firing increased both ATP and H2O2 productions but with different dynamics. In neuropathic MFN2R94Q mice, mimicking Charcot-Marie-Tooth 2A disease, defective mitochondria failed to upregulate ATP production following axonal activity. However, H2O2 production was dramatically sustained. Mimicking demyelinating peripheral neuropathy resulted in a reduced production of ATP while H2O2 level soared. Taken together, our results suggest that ATP and ROS productions are decoupled under neuropathic conditions, which may compromise axonal function and integrity.

neuroscience↗