Biology subjects

McAllister, T.

Publications and source records attributed to McAllister, T..

7 recordsLinked to original sources

bioRxiv2026

Optimizing a Culture-Enriched Hybrid Metagenomics Pipeline to Assess the AMR Footprint of Livestock Manure in Anaerobic Digestate

The role of environmental samples from livestock production systems, including manure and anaerobic digestate, as reservoirs of antimicrobial resistance genes (ARGs) is likely underestimated because conventional metagenomic approaches can overlook low-abundance ARGs and often lack the resolution needed to reliably associate these genes with their microbial hosts and linked mobile genetic elements (MGEs). Here, we evaluated whether culture-enriched metagenomics (CEMG), with and without antibiotic selection, enhances ARG detection in anaerobic digestate and improves the resolution of ARG-MGE-host associations using hybrid short- and long-read metagenomic assembly. Culture enrichment substantially increased ARG recovery, mean ARG abundance rose from 15.4 counts per million (CPM) in culture-independent direct metagenomes from fresh digestate (FD) to 124 CPM in CEMG without antibiotics and 160.0 CPM in antibiotic-selective CEMG, corresponding to an approximately 10.4-fold increase over FD. In FD, only 9 unique ARGs were detected, whereas enrichment recovered 112, including ARGs of clinical importance such as glycopeptide resistance, {beta}-lactamase genes of the CTX-M, OXA, and TEM families, and the cfr 23S rRNA methyltransferase conferring cross- resistance to multiple antibiotic classes. Oxygen availability was the strongest factor structuring enriched community compositions and ARG profiles, with aerobic and anaerobic communities forming distinct clusters. Antibiotic selection induced targeted, class-specific shifts in ARG profiles, with ARGs associated with tetracycline resistance consistently enriched across treatments. Hybrid metagenomic assembly resolved the genomic context of 784 ARGs, of which 59.3% were co-localized with at least one class of mobile genetic element (MGE), predominantly plasmids, insertion sequences, and integrative and conjugative/mobilizable elements (ICEs/IMEs). Biocide and metal resistance genes frequently co-occurred with ARGs on the same contigs, highlighting the potential for co-selection. Together, these findings demonstrate that antibiotic-selective culture enrichment enhances resistome surveillance by improving detection of low-abundance ARGs, while hybrid assembly provides critical genomic context for assessing their mobility and host associations. IMPORTANCELivestock manure and its byproducts, such as anaerobic digestate, are recognized as important environmental reservoirs of antimicrobial resistance genes and resistant bacteria, yet current metagenomic approaches may underestimate this risk by failing to detect low abundance but clinically relevant ARGs. Here, we show that integrating culture enrichment with hybrid metagenomics improves ARG recovery and reveals ARG co-localization with mobile genetic elements and putative bacterial hosts. This approach captures a cultivable and condition- responsive fraction of the resistome that is not readily accessible through direct metagenomic sequencing alone, providing a more informative framework for environmental AMR surveillance.

microbiology↗

bioRxiv2026

Refined USP25/28 inhibitors with improved selectivity towards c-Myc driven squamous lung cancer cells

The ubiquitin specific protease 28 (USP28) is implicated in tumorigenesis by controlling the turnover of substrates including the oncogene c-MYC and the ubiquitin ligase FBW7. Here, we describe small molecule inhibitors of USP25 and USP28, leading to cancer cell cycle arrest and death. However, genetic deletion of USP25/28 does not replicate this effect. An integrated -omics approach revealed off-target effects for thienopyridine and thienopyrazine carboxamide compounds in protein translation. Chemoproteomics and biochemical analyses suggested binding of such compounds to a region near the ribosome complex polypeptide exit tunnel. Structural analysis of a USP28-inhibitor complex enabled the design of modified USP25/28 inhibitor molecules which minimized translation-related off-target effects. In distinction to earlier compounds, the optimized inhibitors were non-toxic to breast cancer cells yet retained potent anti-proliferative activity in squamous lung carcinoma cells, where USP28 is associated with disease progression. Together, our results demonstrate that refined USP25/28 inhibitors can selectively suppress tumor growth by targeting c-MYC driven pathways, offering a more precise therapeutic strategy for treating squamous lung cancers whilst minimizing undesired cytotoxicity.

cancer biology↗

bioRxiv2026

Single-molecule spatial genomics reveals the multi-scale organization and plasticity of extrachromosomal DNA in glioblastoma

Extrachromosomal DNA (ecDNA) is a major driver of intratumoral heterogeneity and is associated with poor clinical outcomes across cancers, yet how individual ecDNA molecules are organized and regulated within intact tumors remains unknown. Here, we leveraged single-molecule, multi-modal spatial genomics to resolve the three-dimensional chromatin organization and transcriptional activity of individual EGFR-containing ecDNA molecules in glioblastoma (GBM) cells in vitro, in orthotopic xenografts, and in patient-derived GBM tissue. At the larger scale, we find that distinct GBM molecular and functional states emerge depending on the local cellular environment. EGFR expression was markedly different between GBM subpopulations, and perturbations of EGFR dosage shifted GBM cellular states. ecDNA expression was modulated by multiple mechanisms, including variation in copy number, chromatin organization, DNA sequence, and chromosomal reintegration, which were simultaneously measured within the same cells. At the single-molecule scale, ecDNA adopts a physically expanded chromatin configuration with larger ecDNA molecules having higher transcriptional activity and interaction with active transcriptional machinery. ecDNA regulation was coordinated within cells and across GBM states, and ecDNA copy number, structure, and transcription were spatially organized across the tumor architecture. Co-culturing GBM cells with neurons recapitulated key features of infiltrative regions, including lower EGFR expression, reduced ecDNA copy number, and increased chromosomal reintegration, suggesting a causal role for the microenvironment in shaping ecDNA regulation. Collectively, these findings support a model in which GBM states and ecDNA are linked, plastic, and influenced by microenvironmental contexts, revealing a previously inaccessible layer of genome organization underlying tumor heterogeneity and malignant cell behavior.

genomics↗

bioRxiv2025

Barley BODYGUARD controls cuticular specialisations regulated by SHINE transcription factors

The outer epidermis of land plants secretes a cuticular layer, a hydrophobic diffusion barrier which minimises water loss into the atmosphere and protects from pests, ultraviolet light and organ fusion. Cuticles typically comprise a polyester cutin matrix embedded and overlaid with cuticular waxes, but their exact chemical make-up, structure and functions can vary widely depending on the tissue and species. Barley shows two such cuticular specialisations: (1) deposition of a thick {beta}-diketone-rich wax bloom on multiple organs at reproductive stage, common in other Poeceae species and linked to yield; and, (2) secretion of a sticky layer on the grain fruit (caryopsis) pericarp cuticle which adheres to inner floral hulls, leading to barleys distinctive covered grain used in animal feed and malting. Two SHINE/WAX-INDUCER transcription factors in barley, HvWIN1 and NUD, promote the wax bloom and hull to caryopsis adhesion, respectively, yet little is understood about other genes involved. Leveraging near-isogenic lines of wax-deficient mutants, we identify the barley BODYGUARD1 (HvBDG1) gene encoding an /{beta}-hydrolase essential for leaf cuticular integrity and wax bloom deposition. Modelling of functional and defective alleles suggests that HvBDG1 N-terminal region control of protein flexibility is important for HvBDG1 function. In addition to their role in controlling barley epicuticular wax deposition, we show that both HvBDG1 and HvWIN1 are essential for strong hull to caryopsis adhesion. Along with NUD, these gene products differentially contribute to ultrastructural changes on the pericarp associated with a cuticular building programme driven by NUD and HvWIN1 regulation of cuticle metabolism and transport and cell wall-related genes, and correlate with shifts in pericarp surface chemistry. We also show that the previously asserted grain-specific role of NUD should be revised, as our findings reveal that it is essential for maintaining leaf cuticle integrity. Our analyses in barley suggest that NUD and HvWIN1 control cuticular specialisations and cuticle integrity in part via promotion of HvBDG1 expression, while HvWIN1 and NUD likely act independently from each other. Lastly, mining tetraploid wheat mutant populations followed by crossing to combine mutated homoeologues demonstrated that BDG1 and WIN1 orthologues also control wax bloom in wheat. Taken together, our work greatly expands the genetic networks and molecular activities important for cuticle development in cereals and the underlying mechanisms for both shared and species-specific cuticular specialisations.

plant biology↗

bioRxiv2024

Elevational and Oceanic Barriers Shape the Distribution, Dispersal and Diversity of Aotearoa's Kapokapowai (Uropetala) Dragonflies

Mountains and islands provide an opportunity for studying the biogeography of diversification and population fragmentation. Aotearoa (New Zealand) is an excellent location to investigate both phenomena due to alpine emergence and oceanic separation. While it would be expected that separation across oceanic and elevation gradients are major barriers to gene flow in animals, including aquatic insects, such hypotheses have not been thoroughly tested in these taxa. By integrating population genomic from sub-genomic Anchored-Hybrid Enrichment sequencing, ecological niche modeling, and morphological analyses from scanning-electron microscopy, we show that tectonic uplift and oceanic vicariance are implicated in speciation and population structure in Kapokapowai (Uropetala) dragonflies. Although Te Moana o Raukawa (Cook Strait), is likely responsible for some of the genetic structure observed, speciation has not yet occurred in populations separated by the strait. We find that the altitudinal gradient across K[a] Tiritiri-o-te-Moana (the Southern Alps) is not impervious but it significantly restricts gene flow between aforementioned species. Our data support the hypothesis of an active colonization of K[a] Tiritiri-o-te-Moana by the ancestral population of Kapokapowai, followed by a recolonization of the lowlands. These findings provide key foundations for the study of lineages endemic to Aotearoa.

evolutionary biology↗

bioRxiv2022

Comparative analysis of macroalgae supplementation on the rumen microbial community: Asparagopsis taxiformis inhibits major ruminal methanogenic, fibrolytic, and volatile fatty acid-producing microbes in vitro

1.Seaweeds have received a great deal of attention recently for their potential as methane-suppressing feed additives in ruminants. To date, Asparagopsis taxiformis has proven a potent enteric methane inhibitor, but it is a priority to identify local seaweed varieties that may hold similar properties. It is essential that any methane inhibitor does not compromise the function of the rumen microbiome. In this study, we conducted an in vitro experiment using the RUSITEC system to evaluate the impact of A. taxiformis, Palmaria mollis, and Mazzaella japonica on rumen prokaryotic communities. 16S rRNA sequencing showed that A. taxiformis had a profound effect on the microbiome, particularly on methanogens. Weighted Unifrac distances showed significant separation of A. taxiformis samples from the control and other seaweeds (P<0.05). Neither P. mollis nor M. japonica had a substantial effect on the microbiome (P>0.05). A. taxiformis reduced the abundance of all major archaeal species (P<0.05), leading to an almost total disappearance of the methanogens. Prominent fibre-degrading and volatile fatty acid (VFA)-producing bacteria including Fibrobacter and Ruminococcus were also inhibited by A. taxiformis (P<0.05), as were other genera involved in propionate production. However, the abundance of many other major bacteria (e.g. Prevotella) was increased by A. taxiformis suggesting the rumen microbiome adapted to an initial perturbation. Our study provides baseline knowledge of microbial dynamics in response to seaweed feeding over an extended period and suggests that feeding A. taxiformis to cattle to reduce methane may directly or indirectly inhibit important fibre-degrading and VFA-producing bacteria.

microbiology↗

bioRxiv2022

A WAX INDUCER1/SHINE transcription factor controls cuticular wax in barley

All land plants seal their above ground body parts with a lipid-rich hydrophobic barrier called the cuticle that protects tissues from dehydration and other terrestrial threats. Mutational studies in several model species, including barley, have resolved multiple loci regulating cuticular metabolism and development. Of particular importance are the eceriferum (cer) mutants characterized by visual alterations in cuticular wax. In barley, some cer mutants, such as cer-x lines, show defects in the distinctive {beta}-diketone-enriched wax bloom on reproductive stage leaf sheaths, stems and spikes. In our study we exploited extensive allelic populations, near-isogenic lines and powerful genotyping platforms to identify variation in the HvWAX INDUCER1 (HvWIN1) gene as causal for cer-x mutants. We show that HvWIN1 function reduces cuticular permeability, promotes the accumulation of {beta}-diketones, and regulates cuticular metabolic gene expression. Analyses across the barley pangenome and hundreds of exome-capture datasets revealed high sequence conservation of HvWIN1 but also two non-synonymous variants exclusive to cultivated germplasm. Taken together, we suggest that variation in HvWIN1 controls multiple cuticular features in barley by controlling the expression of genes involved in cuticle development.

plant biology↗