Biology subjects

Brown, D. G.

Publications and source records attributed to Brown, D. G..

4 recordsLinked to original sources

bioRxiv2026

Longitudinal Changes in Nasal and Oral Microbiome and Antimicrobial Resistance Gene Profiles in Response to Human Fecal Microbiota Transplantation

The gut-lung axis describes interactions between intestinal and respiratory mucosal systems through microbial, metabolic, and immune pathways, but the systemic impact of gut-targeted therapies on upper respiratory tract (URT) communities remains underexplored. We conducted a longitudinal study in adult patients undergoing fecal microbiota transplantation (FMT) for recurrent Clostridioides difficile infection (CDI) alongside healthy controls. Fecal, nasal, and oral samples were collected at baseline (Day 0) and on Days 14 and 56 following FMT. Shotgun metagenomic sequencing was performed to quantify microbial diversity, taxonomic composition, and the abundance of antimicrobial resistance genes (ARGs). FMT was associated with increased gut diversity and decreased levels of key intestinal taxa commonly considered pathobionts, including Klebsiella spp., Escherichia spp., Shigella spp., and Klebsiella pneumoniae. At the phylum level, fecal Bacteroidota increased, while Mucoromycota decreased following treatment. Post-FMT nasal microbiome changes included reduced richness and diversity, expansion of Moraxella, and decreases in taxa linked with respiratory colonization, including Staphylococcus aureus and Streptococcus pneumoniae. By Day 56, nasal communities partially recovered toward healthy profiles. Baseline nasal ARG abundance decreased following FMT, particularly among {beta}-lactam, aminoglycoside, and fluoroquinolone resistance genes, and remained comparable to healthy controls by Day 56. In contrast, the oral microbiome and oral resistome remained largely stable, with only minor fluctuations, and no consistent increases in respiratory pathobiont-associated taxa. In summary, FMT was associated with broader effects beyond the gut, including changes in the URT microbial ecology and antimicrobial resistance profiles. Together, these findings are consistent evidence of gut-lung microbial interactions, linking intestinal dynamics with respiratory microbial composition and antimicrobial resistance patterns.

microbiology↗

bioRxiv2021

Opposing roles of p38α phosphorylation and arginine methylation in driving TDP-43 proteinopathy.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder typically characterized by insoluble inclusions of hyperphosphorylated TDP-43. The mechanisms underlying toxic TDP-43 accumulation are not understood. Persistent activation of p38 mitogen-activated protein kinase (MAPK) is implicated in ALS. However, it is unclear how p38 MAPK affects TDP-43 proteinopathy. Here, we demonstrate that inhibition of p38 MAPK reduces pathological TDP-43 phosphorylation, aggregation, cytoplasmic mislocalization, and neurotoxicity. We establish that p38 MAPK phosphorylates TDP-43 at pathological serine 409/410 (S409/S410) and serine 292 (S292), which reduces TDP-43 liquid-liquid phase separation (LLPS) but allows pathological TDP-43 aggregation. Moreover, we show that protein arginine methyltransferase 1 methylates TDP-43 at R293. Importantly, S292 phosphorylation reduces R293 methylation, and R293 methylation reduces S409/S410 phosphorylation. R293 methylation permits TDP-43 LLPS and reduces pathological TDP-43 aggregation. Thus, strategies to reduce p38-mediated TDP-43 phosphorylation and promote R293 methylation could have therapeutic utility for ALS and related TDP-43 proteinopathies.

molecular biology↗

bioRxiv2020

Talin Rod Domain Containing Protein 1 (TLNRD1) is a novel actin- bundling protein which promotes filopodia formation

Talin is a mechanosensitive adapter protein which couples integrins to the cytoskeleton and regulates integrin-mediated adhesion. Talin rod domain-containing protein-1 (TLNRD1) shares 22% homology with the R7R8 domains of talin, and is highly conserved throughout vertebrate evolution, however little is known about its function. Here we show that TLNRD1 is an -helical protein which shares the same atypical topology as talin R7R8, but forms a novel antiparallel dimer arrangement. Actin co-sedimentation assays and electron microscopy reveal TLNRD1 is an actin-bundling protein that forms tight actin bundles. In addition, TLNRD1 binds to the same LD-motif containing proteins, RIAM and KANK, as talin, and thus may act in competition with talin. Filopodia are cell protrusions supported by tightly bundled actin filaments and TLNRD1 localises to filopodia tips, increases filopodia number and promotes cell migration in 2D. Together our results suggest that TLNRD1 has similar functionality to talin R7R8, serving as a nexus between the actin and microtubule cytoskeletons independent of adhesion complexes.

cell biology↗

bioRxiv2019

Exogenous alginate protects Staphylococcus aureus from killing by Pseudomonas aeruginosa

Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are mono-infected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can co-exist with S. aureus in vitro due to transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm co-culture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to transcriptional downregulation of pvdA, a gene required for the production of the iron scavenging siderophore pyoverdine, as well as down-regulation of the PQS (Pseudomonas quinolone signal; 2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that co-culture of mucoid P. aeruginosa with non-mucoid P. aeruginosa can mitigate the killing of S. aureus by the non-mucoid strain of P. aeruginosa, indicating that the mechanism we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability kill S. aureus at late time points, and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the effects of mucoidy in a strain-specific manner.\n\nIMPORTANCECF patients are chronically infected by polymicrobial communities of microorganisms. The two dominant bacterial pathogens that infect CF patient lungs are P. aeruginosa and S. aureus, with [~]30% of patients co-infected by both species. Patients infected with both P. aeruginosa and S. aureus have worse outcomes than mono-infected patients, and both species persist within the same physical space in the lungs of CF patients. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus co-existence, despite evidence that P. aeruginosa kills S. aureus when these organisms are co-cultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to co-exist in proximal physical space, will lead to better informed treatments for chronic polymicrobial infections.

microbiology↗