Biology subjects

Goodhead, I. B.

Publications and source records attributed to Goodhead, I. B..

5 recordsLinked to original sources

bioRxiv2025

Hybrid short- and long-read assembly of an experimentally evolved Sodalis glossinidius strain SgGmmC1*

Bacterial symbionts of insects undergo dramatic genome reduction during their evolutionary transition from free-living to host-dependent lifestyles, but the dynamics of this process remain poorly understood due to the difficulty of observing these processes in real-time. Sodalis glossinidius, a facultative endosymbiont of tsetse flies, provides an exceptional opportunity to study this transition experimentally: Unlike highly specialised obligate symbionts, S. glossinidius can be cultured in vitro and retains a large genome (4 Mbp) with extensive pseudogene content (49%), suggesting a recent evolutionary transition. Here, we present a comparative genomic analysis of S. glossinidius strains isolated from laboratory colony-derived Glossina morsitans morsitans, comparing one after ten years of serial passaging in laboratory culture (SgGmmC1*) to a counterpart isolated at the same time (SgGmmB4). Hybrid genome assembly using Oxford Nanopore and Illumina technologies produced a high-quality 4.29 Mbp genome comprising one circular chromosome and four plasmids similar. Comparative analysis revealed a significant deletion (17,209 bp) containing 31 genes, including (involved in thiamine biosynthesis) and genes encoding sulfur transporters. Additionally, we identified multiple small-scale mutations (8 deletions, 39 insertions, 10 SNPs) resulting in frameshifts in genes including a hemolysin precursor (shlA). Our findings demonstrate that, under stable laboratory conditions without the selective pressures of the host environment, S. glossinidius continues to undergo genome degradation. The loss of thiM supports previous hypotheses of complementary metabolic pathways between S. glossinidius and the primary symbiont Wigglesworthia glossinidia for thiamine biosynthesis. This study provides insights into the evolutionary trajectory of facultative symbionts and has implications for paratransgenic approaches using S. glossinidius for trypanosome control. DATA SUMMARYRaw Nanopore and MiSeq reads are available in the European Nucleotide Archive under Project PRJEB32321 (Read accessions: ERX3321202 and ERX3321201 respectively). A full GBK formatted annotation of SgGmmC1* has been deposited in Figshare at https://doi.org/10.17866/rd.salford.8052437.v1. IMPACT STATEMENTIn this study we provide new insights into the ongoing genome degradation of Sodalis glossinidius, a facultative endosymbiont of tsetse flies implicated in their ability to transmit trypanosomiasis, during prolonged laboratory culture. Through high-quality comparative genomics we reveal significant gene loss and mutational changes, including disruption of pathways involved in nutrient biosynthesis. These findings enhance our understanding of symbiont genome evolution and inform the development of S. glossinidius as a potential tool for paratransgenic strategies in controlling trypanosome transmission.

genomics↗

bioRxiv2023

Comparison of dental topography of marmosets and tamarins (Callitrichidae) to other platyrrhine primates using a novel freeware pipeline

Dental topographic metrics (DTMs), which quantify different aspects of the shape of teeth, are powerful tools for studying dietary adaptation and evolution in mammals. However, comparative samples of scanned mammal teeth suitable for analysis with DTMs remain limited in size and scope, with little or no representation of some major lineages, even within well-studied clades such as primates. In addition, current DTM protocols usually rely on proprietary software, which may be unavailable to many researchers for reasons of cost. We address these issues in the context of a DTM analysis of the primate clade Platyrrhini ("New World monkeys") by: 1) presenting a large comparative sample of scanned second lower molars (m2s) of callitrichids (marmosets and tamarins), which were previously underrepresented in publicly available platyrrhine datasets; and 2) giving full details of an entirely freeware pipeline for DTM analysis. We also present an updated discrete dietary classification scheme for extant platyrrhines, based on cluster analysis of dietary data extracted from 98 primary studies. Our freeware pipeline performs equally well in dietary classification accuracy of an existing sample of platyrrhine m2s (excluding callitrichids) as a published protocol that uses proprietary software, at least when multiple DTMs are combined. Individual DTMs however, sometimes showed very different results in classification accuracies between that of our freeware pipeline and that of the proprietary protocol, most likely due to the differences in the smoothing functions used. The addition of callitrichids still resulted in high classification accuracy in predicting diet with combined DTMs, although accuracy was considerably higher when molar size was included (90%) than excluded (73%). We conclude that our new freeware DTM pipeline is capable of accurately predicting diet in platyrrhines based on tooth shape and size, and so is suitable for inferring probable diet of taxa for which direct dietary information is unavailable, such as fossil species.

evolutionary biology↗

bioRxiv2021

Comparative analysis of gene prediction tools for viral genome annotation

The number of newly available viral genomes and metagenomes has increased exponentially since the development of high throughput sequencing platforms and genome analysis tools. Bioinformatic annotation pipelines are largely based on open reading frame (ORF) calling software, which identifies genes independently of the sequence taxonomical background. Although ORF-calling programs provide a rapid genome annotation, they can misidentify ORFs and start codons; errors that might be perpetuated and propagated over time. This study evaluated the performance of multiple ORF-calling programs for viral genome annotation against the complete RefSeq viral database. Programs outputs varied when considering the viral nucleic acid type versus the viral host. According to the number of ORFs, Prodigal and Metaprodigal were the most accurate programs for DNA viruses, while FragGeneScan and Prodigal generated the most accurate outputs for RNA viruses. Similarly, Prodigal outperformed the benchmark for viruses infecting prokaryotes, and GLIMMER and GeneMarkS produced the most accurate annotations for viruses infecting eukaryotes. When the coordinates of the ORFs were considered, Prodigal scored high for all scenarios except for RNA viruses, where GeneMarkS generated the most reliable results. Overall, the quality of the coordinates predicted for RNA viruses was poorer than for DNA viruses, suggesting the need for improved ORF-calling programs to deal with RNA viruses. Moreover, none of the ORF-calling programs reached 90% accuracy for annotation of DNA viruses. Any automatic annotation can still be improved by manual curation, especially when the presence of ORFs is validated with wet-lab experiments. However, our evaluation of the current ORF-calling programs is expected to be useful for the improvement of viral genome annotation pipelines and highlights the need for more expression data to improve the rigor of reference genomes.

bioinformatics↗

bioRxiv2020

Antibiotic resistance profiles and population structure of disease-associated Staphylococcus aureus infecting patients in Fort Portal Regional Referral Hospital, Western Uganda

Tackling antimicrobial resistance (AMR) is particularly challenging in low-resource settings such as Fort Portal Regional Referral Hospital (FPRRH) in Western Uganda. Specific knowledge of local AMR epidemiology is required to inform evidence-based improvement of antibiotic stewardship measures in the hospital. To address this, we combined existing antimicrobial susceptibility testing (AST) from FPRRH, with whole genome sequencing (WGS) of 41 Staphylococcus aureus isolates (2017-2019). AST revealed 73% (30/41) of isolates were resistant to one or more antibiotics and 29% (12/41) were multi-drug resistant (MDR). Resistance phenotypes were largely explained by the presence of antibiotic resistance genes in WGS data. Five isolates were methicillin-resistant S. aureus (MRSA) and MDR. Although all isolates were susceptible to clindamycin, a 24% carriage of erm genes suggests potential for rapid development of resistance. We inferred a population structure for the S. aureus isolates by comparing their core genomes. Twenty isolates formed a tight cluster corresponding to multilocus sequence typing clonal complex (CC) 152, a CC found to be particularly prevalent in northern Africa. The frequency of genes associated with methicillin, chloramphenicol and ciprofloxacin resistance were significantly lower among CC152 strains than non-CC152 strains; thus, in keeping with previous work, we find that CC152 is almost exclusively methicillin-sensitive S. aureus (MSSA). Also, in agreement with other studies, we observed that the occurrence of Panton-Valentine leukocidin toxin-encoding genes was significantly higher among CC152 strains than non-CC152 strains. However, we also observed that the coagulase gene was over-represented in this CC, further defining the virulence strategy of this important pathogen. By generating detailed information about the epidemiology of circulating S. aureus and their antibiotic susceptibility, our study has provided, for the first time, data on which evidence-based infection and AMR interventions at FPRRH can be based.

microbiology↗

bioRxiv2019

Functional genomics of a symbiotic community: shared traits in the olive fruit fly gut microbiota

The olive fruit fly Bactrocera oleae is a major pest of olives worldwide and houses a specialized gut microbiota dominated by the obligate symbiont \"Candidatus Erwinia dacicola\". Ca. E. dacicola is thought to supplement dietary nitrogen to the host, with only indirect evidence for this hypothesis so far. Here, we sought to investigate the contribution of the symbiosis to insect fitness and explore the ecology of the insect gut. For this purpose, we examined the composition of bacterial communities associated with Cretan olive fruit fly populations, and inspected several genome and transcriptome assemblies. We identified, and reconstructed the genome of, a novel component of the gut microbiota, Tatumella sp. TA1, which is stably associated with Mediterranean olive fruit fly populations. We also reconstructed a number of pathways related to nitrogen assimilation and interaction with the host. The results show that, despite variation in taxa composition of the gut microbial community, core functions related to the symbiosis are maintained. Functional redundancy between different microbial taxa was observed for genes allowing urea hydrolysis. The latter is encoded in the obligate symbiont genome by a conserved urease operon, likely acquired by horizontal gene transfer, based on phylogenetic evidence. A potential underlying mechanism is the action of mobile elements, especially abundant in the Ca. E. dacicola genome. This finding, along with the identification, in the studied genomes, of extracellular surface structure components that may mediate interactions within the gut community, suggest that ongoing and past genetic exchanges between microbes may have shaped the symbiosis.

evolutionary biology↗