Biology subjects

Westmacott, G.

Publications and source records attributed to Westmacott, G..

4 recordsLinked to original sources

bioRxiv2026

Non-homologous end-joining is implicated in rapid and efficient caspofungin adaptation in Nakaseomyces glabratus

Antifungal resistance in Nakaseomyces glabratus is a major clinical challenge, yet the cellular processes that shape its evolution remain poorly understood. Here, we used experimental evolution to investigate the role of the error-prone double-strand break repair pathway, non-homologous end joining (NHEJ), in adaptation to fluconazole and caspofungin. Wild-type and NHEJ-deficient (lig4{Delta}) populations were evolved under antifungal selection for 25 days. Fluconazole resistance emerged rapidly in both genetic backgrounds and was associated with recurrent PDR1 mutations and aneuploidies. In contrast, caspofungin adaptation was delayed and less efficient in lig4{Delta} populations, with several lineages failing to survive. All wild-type caspofungin-evolved isolates carried canonical FKS2 hotspot mutations, whereas lig4{Delta} isolates predominantly acquired resistance through alternative genetic pathways. Caspofungin adaptation also frequently conferred cross-resistance to fluconazole and was accompanied by changes in the abundance of ergosterol-associated proteins. Together, these findings implicate NHEJ in promoting efficient evolution of FKS-mediated echinocandin resistance and demonstrate that DNA repair capacity can shape antifungal resistance trajectories in N. glabratus.

microbiology↗

bioRxiv2026

Characterization of Atypical Ebola Virus Disease in Ferrets

Ebola virus (EBOV) typically results in a severe--and often lethal--acute disease. However, increasing evidence suggests that EBOV can persist in certain immune-privileged tissues, which may then serve as reservoirs for the later reemergence of EBOV and disease recrudescence. Here, we report atypical EVD recrudescence in a ferret model inoculated with an otherwise lethal dose of EBOV and treated with low doses of a highly potent monoclonal antibody cocktail. Among 32 antibody-treated ferrets, 14 animals survived, while 8 succumbed to acute EVD within about 5-8 days. The remaining 10 animals succumbed to atypical EVD between 12 and 18 days post-infection (DPI) despite having shown no, or very minor, signs of illness during the acute phase of disease. While viremia disappeared by 14 DPI in most animals that succumbed to atypical EVD, it rebounded modestly just prior to death. Unlike animals that died of acute EVD, those that died of atypical EVD showed only a moderate systemic inflammatory response and few signs of organ dysfunction, in line with low levels of virus in the liver and spleen. Interestingly, however, ferrets that died of atypical EVD showed high levels of virus in the brain, consistent with increased markers of inflammation in the central nervous system and significant pathological changes, including a breakdown in the blood-brain barrier and severe meningoencephalitis. Not only does this study shed important light on the atypical and underappreciated manifestations of EVD, but it also establishes the ferret as a valuable model of EBOV persistence and recrudescence. AUTHOR SUMMARYOver the last several years, it has become increasingly apparent that Ebola virus is capable of persisting in survivors and, occasionally, reemerging to cause a recrudescent disease that is often distinct from the acute illness and characterized by neurological involvement. Since nearly all existing Ebola virus animal models are uniformly lethal, it has been difficult to understand the processes that lead to persistence and atypical manifestations of disease. In this study, we describe a late-onset, atypical Ebola virus disease in ferrets that was characterized by high levels of virus in the brain and significant markers of brain inflammation. Our comprehensive analysis of the pathogenic processes that contributed to this disease not only provides critical insight into Ebola virus persistence and recrudescence, but it also establishes the ferret as the first tractable model for investigating these atypical outcomes.

microbiology↗

bioRxiv2024

A role for the putative error-prone polymerase REV1 in DNA damage and antifungal drug resistance in Candida albicans

Antimicrobial-induced DNA damage, and subsequent repair via upregulation of DNA repair factors, including error-prone translesion polymerases, can lead to the increased accumulation of mutations in the microbial genome, and ultimately increased risk of acquired mutations associated with antimicrobial resistance. While this phenotype is well described in bacterial species, it is less thoroughly investigated amongst microbial fungi. Here, we monitor DNA damage induced by antifungal agents in the fungal pathogen Candida albicans, and find that commonly used antifungal drugs are able to induce DNA damage, leading to the upregulation of transcripts encoding predicted error-prone polymerases and related factors. We focus on REV1, encoding a putative error-prone polymerase, and find that while deleting this gene in C. albicans leads to increased sensitivity to DNA damage, it also unexpectedly renders cells more likely to incur mutations and evolve resistance to antifungal agents. We further find that deletion of REV1 leads to a significant depletion in the uncharacterized protein Shm1, which itself plays a role in fungal mutagenesis. Together, this work lends new insight into previously uncharacterized factors with important roles in the DNA damage response, mutagenesis, and the evolution of antifungal drug resistance.

microbiology↗

bioRxiv2020

Phenotypic and multi-omics characterization of Escherichia coli K-12 adapted to quaternary ammonium compounds identifies lipid A and cell envelope alterations regulated by mar-sox-rob and stress inducible pathways

Quaternary ammonium compounds (QACs) benzalkonium (BZK) and cetrimide (CET) are common disinfectants used to inhibit or eradicate Gram-negative bacteria in clinical and agricultural products. QAC tolerance in Escherichia coli and other Enterobacterales species can confer cross-resistance to various clinically used antibiotics, making it important to understand mechanisms of QAC tolerance in greater depth. QAC adaptation by E. coli is hypothesized to alter MarRAB regulated genes that converge on the outer membrane, specifically, lipid A biosynthesis and transport genes, porins, and efflux pump systems. To test this, we performed a multi-omics and phenotypic characterization of E. coli K-12 adapted to BZK and CET, to assess how QACs alter cell growth, genomics, and proteomics. E. coli adapted to either BZK and CET resulted in strains with stable QAC tolerance when either drug was omitted, elongated and narrower cell morphologies by scanning electron microscopy, and reduced growth fitness when compared to un-adapted E. coli. Antimicrobial susceptibility testing revealed that QAC adaptation increased E. coli tolerance by [≥]4-fold to BZK, CET, and other QACs but no antibiotic cross-resistance. Single nucleotide variants identified by whole genome sequencing and differentially accumulated proteins by liquid chromatography-mass spectrometry identified alterations to various QAC-adapted E. coli genes and proteins belonging to: lipid A biosynthesis and transport (lpxLM, msbA, mla), the mar-sox-rob regulatory pathway (marR, rob), DNA/protein translation (gyrA, rpsA, rpoB, rapA). These alterations validate the hypothesis that mar-sox-rob network plays a role in QAC tolerance and identifies additional stress inducible genetic and protein QAC tolerant biomarkers. ImportanceBacterial tolerance mechanisms associated with disinfectant QAC adaptation is hypothesized to overlap with the mar-sox-rob multiple antimicrobial resistance pathway but has not been directly shown. Here, we generate QAC tolerant E. coli strains and identify phenotypic changes associated with protein and genetic alterations caused by prolonged QAC exposure. We identified genes that overlap with known antibiotic resistance mechanisms as well as distinct genes and proteins specific to QAC adaptation that are useful for future bacterial disinfectant tolerance mechanism studies. However, these altered genes and proteins implicate MarR and Rob pathways specifically in QAC tolerance but, surprisingly, the involvement of mar-sox-rob pathways did not increase antibiotic cross-resistance. Many altered genes we identified were essential genes in lipid A biosynthesis/transport, DNA and RNA transcription, and protein regulation systems potentially explaining why only QAC cross-tolerance was observed and why we observed greater cell fitness costs despite MarR and Rob pathway involvement.

microbiology↗