Biology subjects

Millard, A.

Publications and source records attributed to Millard, A..

13 recordsLinked to original sources

bioRxiv2026

Redefining accessible food resources for paleodietary reconstruction in Britain: baseline recommendations based on isotopic data synthesis

Paleodietary reconstruction requires isotopic data from both humans and their accessible food resources. However, ideally defined accessible food resources, namely those from the same sites and periods as the target human individuals, are not always available for all ancient individuals. The number of sites with human C/N isotopic data far exceeds that with food-resource isotopic data. Consequently, many individuals cannot be linked to corresponding accessible food resources, a limitation that becomes more pronounced in large-scale quantitative dietary reconstructions incorporating a wide range of food-resource categories. Therefore, this study aims to broaden the definition of accessible food resources. To achieve this aim, we compiled food-resource and soil isotopic data ({delta}13C and {delta}15N) from Britain, including 4,012 ancient faunal and plant remains, 394 modern plant samples, and 260 modern soil samples. Region-period combined groups were established for the five major food-resource categories and served as the basic analytical units for detailed isotopic comparisons. Based on these comparisons, we propose broader criteria for defining accessible food resources. No significant intra-group variation was observed in the isotopic values of terrestrial herbivores and omnivores, suggesting that animals within each region-period combined group can serve as accessible food resources for humans from the same group. C3 plants showed substantial spatial variation but limited temporal variation. Accordingly, accessible food resources for C3 plants should be defined by region, namely England, Wales, and Scotland, regardless of chronological period, with humans from each region assigned plant data from their respective region. Marine and freshwater fish showed no clear temporal or spatial variation, and therefore unified datasets can be applied across all human individuals. Our findings enable each ancient human individual to be assigned appropriate accessible food resources, and therefore appropriate food-resource isotope baselines. We further demonstrate that such assignments can effectively reduce sampling bias arising from the use of traditionally defined accessible food resources, which are often limited by small sample sizes.

ecology↗

bioRxiv2026

Diverse phages of ammonia oxidizers with the potential to modulate nitrification

Agriculture is a major source of anthropogenic greenhouse-gas emissions and the largest source of nitrous oxide (N2O), an extremely potent greenhouse gas and ozone-depleting agent. Soil N2O emissions are largely driven by nitrification, in which ammonia-oxidizing microorganisms catalyze the oxidation of ammonia to nitrite. Nitrification not only mediates N2O fluxes but also reduces fertilization efficiency and contributes to eutrophication through nitrate leaching.\ Bacteriophage (phage)-based control of microbial communities is gathering interest; however, phages infecting ammonia-oxidizers are mostly uncharacterized, with only one lytic phage having been described, limiting the potential for developing phage-mediated nitrification control. Here, we characterized the largest set of cultivated phages infecting ammonia-oxidizing bacteria (AOB) to date: 45 dsDNA phages collected from urban wastewater, infecting four AOB species, with 16 demonstrating cross-genus host ranges and capable of eliminating nitrification activity in liquid cultures. Phylogenetic and taxonomic analyses revealed six proposed families of Caudoviricetes and several monophyletic clades, likely representing higher-level lineages. Structure-guided genome annotation revealed a diverse collection of auxiliary metabolic genes encoded by phage, ranging from a complete ABC transporter cassette to a large antimicrobial resistance gene cluster. These results unveil previously unrecognized diversity of cultivated AOB phages and their potential to alter host physiology. Our data describes a broad taxonomic and functional repertoire of cultured AOB phages, suggesting that viruses play a significant and complex role in nitrification. Moreover, we outline an effective methodological framework for isolating AOB phages from environmental samples. These results reframe our understanding of environmental nitrification and enable intensified cultivation, characterization and use of phages for its control.

microbiology↗

bioRxiv2025

Bacteriophage pharmacodynamics studied in an in vitro pharmacokinetic model of infection

SynopsisO_ST_ABSBackgroundC_ST_ABSBacteriophage therapy offers an alternative way to counter the menace of increasing antimicrobial resistance. Despite its use in clinical practice for many decades the basic tools to study the translational pharmacodynamics of phages are not available and it is recognised that lack of understanding of phage pharmacokinetic/dynamics (PK/PD) is a severe limitation in individual patient use and clinical trial design. MethodsTraditional in vitro PK/PD evaluation tools were used to assess the antibacterial effect of single exposures of a bacteriophage cocktail against 4 strains of E. coli with potentially different patterns of response to phage. Initially, time-kill curves (TKC) were performed over 48hr and subsequently a dilutional in vitro model (IVM) was used to assess the antibacterial effects over 72hr. ResultsIn TKC, the four E. coli strains showed different patterns of kill and regrowth when exposed to phage with two strains showing a sustained drop in bacterial viable count and two showing initial kill and regrowth. Using the IVM similar bacterial pharmacodynamic patterns were observed, and phage titre increased inversely but consistently with E. coli kill. ConclusionsAn In vitro dilutional model can be used to study the antibacterial effect of a phage cocktail on E.coli showing strain-to-strain variation in bacterial killing and bacteriophage titre. Such models can be used to provide more nuanced information on phage pharmacokinetics/dynamics and translationally useful information for dosing in humans.

microbiology↗

bioRxiv2024

The relationship between microbial community succession, decay, and anatomical character loss in non-biomineralised animals

A fundamental assumption of hypothesis-driven decay experiments is that, during decay, the loss of anatomy follows a sequence broadly controlled by the intrinsic compositional properties of tissues. Recent work investigating the succession of postmortem endogenous microbial communities (thanatomicrobiome) challenges this assumption. These studies suggest the thanatomicrobiome exhibits a predictable, clock-like succession in response to physical and chemical environmental changes within a carcass. Therefore, it is possible that reproducible sequences of character loss during decay are controlled by thanatomicrobiome succession dynamics. If so, exceptionally preserved fossil anatomy would reflect a succession of ancient contemporaneous microbial communities, about which we know nothing, rendering decay experiments uninformative. Here, we investigate two questions: (1) what is the role of exogenous and endogenous bacteria during formation of the thanatomicrobiome and (2) do thanatomicrobiome successions control the sequence of anatomical character loss within a decaying carcass? Our analysis shows that the thanatomicrobiome is dominated by endogenous bacteria and that, even in the presence of inoculum, exogenous bacteria do not invade the carcass and replace native bacteria (while the carcass is intact). This confirms that the use of environmental inoculum in decay experiments introduces an inadvisable confounding variable. Secondly, we find no correlation between thanatomicrobiome successions and the sequence of anatomical character loss, supporting that fossil non-biomineralised characters correlate with their propensity to decay in extant relatives. These findings indicate that the inability to model ancient bacteria does not invalidate decay experiments. We also present a synthesis of the role of bacteria in non-biomineralised fossilisation.

paleontology↗

bioRxiv2023

Genomic plasticity is a blueprint of diversity in Salmonella lineages

The flexible genome, organised in regions of genomic plasticity (RGP), serves as a potent facilitator of the dynamic evolution of bacterial genomes through gene acquisition and loss. Here we explored the genomic plasticity across Salmonella lineages, revealing a purposeful, non-random integration pattern of pathogenicity-related gene clusters into specific RGP. Noteworthy examples include the correlation between the type I-E CRISPR-Cas system, gold tolerance, and specific RGP. The scattered prevalence of RGP across Salmonella lineages profoundly shapes the pathogenicity makeup of Salmonella strains. The preferences of RGP seem guided by conserved flanking genes that likely share regulatory and functional coordination. For example, metal resistance genes are predominant in RGP positioned near stress resistance genes, indicating a regulatory network to efficiently counter stressors. Additionally, we observed that different plasmid incompatibility types and prophage genera carry distinct pathogenicity genes. Similar to RGP, their distribution across Salmonella lineages plays a critical role in defining pathogenicity. By uncovering these intricate connections among gene clusters, RGP, mobile genetic elements, and pathogenic attributes, our study offers novel insights into the evolutionary trajectory of Salmonella and holds promise for predicting future adaptations and developing targeted interventions against infections.

microbiology↗

bioRxiv2022

Ecological and evolutionary patterns of virus-host interactions throughout a grassland soil depth profile

BackgroundSoil microbes play pivotal roles in global carbon cycling, however the fundamental interactions between microbes and their infecting viruses remain unclear. This is exacerbated with soil depth, where the patterns of viral dispersal, ecology, and evolution are markedly underexplored. To investigate viral communities across soil depth, we leveraged a publicly available metagenomic data set sampled from grassland soil in northern California. Results10,196 non-redundant vOTUs were recovered from soil sampled from 20 cm to 120 cm below the surface. Viral prevalence was high throughout the soil depth profile, with viruses infecting dominant soil phyla, including Actinomycetota. Contrary to leading hypotheses, lysogeny did not dominate in the soil viral communities. Viral diversity was investigated at both the population-level (i.e., macro diversity) and strain-level (i.e., micro diversity) to reveal diverse ecological and evolutionary patterns of virus-host interactions in surface and subsurface soil. ConclusionsBy investigating viral micro diversity in soil for the first time, we have uncovered patterns of antagonistic co-evolution across both surface and subsurface soils. Furthermore, we have provided evidence of soil viruses augmenting the remineralisation of soil carbon. While we continue to yield a more comprehensive understanding of soil viral ecology, our work appeals to future researchers to continue to investigate subsurface viral communities.

ecology↗

bioRxiv2022

Crop management shapes the diversity and activity of DNA and RNA viruses in the rhizosphere

BackgroundThe rhizosphere is a hotspot for microbial activity and contributes to ecosystem services including plant health and biogeochemical cycling. The activity of microbial viruses, and their influence on plant-microbe interactions in the rhizosphere, remains undetermined. Given the impact of viruses on the ecology and evolution of their host communities, determining how soil viruses influence microbiome dynamics is crucial to build a holistic understanding of rhizosphere functions. ResultsHere, we aimed to investigate the influence of crop management on the composition and activity of bulk soil, rhizosphere soil, and root viral communities. We combined viromics, metagenomics, and metatranscriptomics on soil samples collected from a 3-year crop rotation field trial of oilseed rape (Brassica napus L.). By recovering 1,059 dsDNA viral populations and 16,541 ssRNA bacteriophage populations, we expanded the number of underexplored Leviviricetes genomes by > 5 times. Through detection of viral activity in metatranscriptomes, we uncovered evidence of "Kill-the-Winner" dynamics, implicating soil bacteriophages in driving bacterial community succession. Moreover, we found the activity of viruses increased with proximity to crop roots and identified that soil viruses may influence plant-microbe interactions through the reprogramming of bacterial host metabolism. We have provided the first evidence of crop rotation-driven impacts on soil microbial communities extending to viruses. To this aim, we present the novel principal of "viral priming", which describes how the consecutive growth of the same crop species primes viral activity in the rhizosphere through local adaptation. ConclusionsOverall, we reveal unprecedented spatial and temporal diversity in viral community composition and activity across root, rhizosphere soil and bulk soil compartments. Our work demonstrates that the roles of soil viruses need greater consideration to exploit the rhizosphere microbiome for food security, food safety, and environmental sustainability.

ecology↗

bioRxiv2021

Identification of a new family of "megaphages" that are abundant in the marine environment

Megaphages - bacteriophages harbouring extremely large genomes - have recently been found to be ubiquitous, being described from a variety of microbiomes ranging from the animal gut to soil and freshwater systems. However, no complete marine megaphage has been identified to date. Here, using both short and long read sequencing, we assembled >900 high-quality draft viral genomes from water in the English Channel. One of these genomes included a novel megaphage, Mar_Mega_1 at >650 Kb, making it one of the largest phage genomes assembled to date. Utilising phylogenetic and network approaches, we found this phage represents a new family of bacteriophages. Genomic analysis showed Mar_Mega_1 shares relatively few homologues with its closest relatives, but, as with other mega-phages Mar_Mega_1 contained a variety of auxiliary metabolic genes responsible for carbon metabolism and nucleotide biosynthesis, including isocitrate dehydrogenase [NADP] and nicotinamide-nucleotide amidohydrolase [PncC] which have not previously been identified in megaphages. The results of this study indicate that phages containing extremely large genomes can be found in abundance in the marine environment and augment host metabolism by mechanisms not previously described.

microbiology↗

bioRxiv2020

Analysis of selection methods to develop novel phage therapy cocktails against antimicrobial resistant clinical isolates of bacteria

Antimicrobial resistance (AMR) is a major problem globally. The main bacterial organisms associated with urinary tract infection (UTI) associated sepsis are E. coli and Klebsiella along with Enterobacter species. These all have AMR strains known as ESBL (Extended Spectrum Beta-Lactamase), which are featured on the WHO priority pathogens list as critical for research. Bacteriophages (phages) as viruses that can infect and kill bacteria, could provide an effective tool to tackle these AMR strains. There is currently no gold standard for developing a phage cocktail. Here we describe a novel approach to develop an effective phage cocktail against a set of ESBL-producing E. coli and Klebsiella largely isolated from patients in UK hospitals. By comparing different measures of phage efficacy, we show which are the most robust, and suggest an efficient screening cascade that could be used to develop phage cocktails to target other AMR bacterial species. A target panel of 38 ESBL-producing clinical strains isolated from urine samples was collated and used to test phage efficacy. After an initial screening of 68 phages, six were identified and tested against these 38 strains to determine their clinical coverage and killing efficiency. To achieve this, we assessed four different methods to assess phage virulence across these bacterial isolates. These were the Direct Spot Test (DST), the Efficiency of Plating (EOP) assay, the planktonic killing assay and the biofilm assay. The final ESBL cocktail of six phages could effectively kill 23/38 strains (61%) for Klebsiella 13/19 (68%) and for E. coli 10/19 (53%) based on the planktonic killing assay data. The ESBL E. coli collection had six isolates from the prevalent UTI-associated ST131 sequence type, five of which were targeted effectively by the final cocktail. Of the four methods used to assess phage virulence, the data suggests that planktonic killing assays are as effective as the much more time-consuming EOPs and data for the two assays correlates well. This suggests that planktonic killing is a good proxy to determine which phages should be used in a cocktail. This assay when combined with the virulence index also allows phage synergy to inform cocktail design.

microbiology↗

bioRxiv2020

Rapid discovery of novel prophages using biological feature engineering and machine learning

Prophages are phages that are integrated into bacterial genomes and which are key to understanding many aspects of bacterial biology. Their extreme diversity means they are challenging to detect using sequence similarity, yet this remains the paradigm and thus many phages remain unidentified. We present a novel, fast and generalizing machine learning method based on feature space to facilitate novel prophage discovery. To validate the approach, we reanalyzed publicly available marine viromes and single-cell genomes using our feature-based approaches and found consistently more phages than were detected using current state-of-the-art tools while being notably faster. This demonstrates that our approach significantly enhances bacteriophage discovery and thus provides a new starting point for exploring new biologies.

bioinformatics↗

bioRxiv2020

The ecogenomics of dsDNA bacteriophages in feces of stabled and feral horses

The viromes of the mammalian lower gut were shown to be heavily dominated by bacteriophages; however, only for humans were the composition and intervariability of the bacteriophage communities studied in depth. Here we present an ecogenomics survey of dsDNA bacteriophage diversity in the feces of horses (Equus caballus), comparing two groups of stabled horses, and a further group of feral horses that were isolated on an island. Our results indicate that the dsDNA viromes of the horse feces feature higher richness than in human viromes, with more even distribution of genotypes. No over-represented phage genotypes, such as CrAssphage-related viruses found in humans, were identified. Additionally, many bacteriophage genus-level clusters were found to be present in all three geographically isolated populations. The diversity of the horse intestinal bacteriophages is severely undersampled, and so consequently only a minor fraction of the phage contigs could be linked with the bacteriophage genomes. Our study indicates that bacteriophage ecological parameters in the intestinal ecosystems in horses and humans differ significantly, leading them to shape their corresponding viromes in different ways. Therefore, the diversity and structure of the intestinal virome in different animal species needs to be experimentally studied. Short abstract (needed in some journals as eLife)The viromes of the mammalian gut were shown to be heavily dominated by bacteriophages; however, only for humans were the composition and intervariability of the bacteriophage communities studied in depth. Here we present an ecogenomics survey of dsDNA bacteriophage diversity in the feces of horses (Equus caballus), comparing stabled horses, and feral horses that were isolated on an island. The viromes equine fecal viromes feature higher richness than in human viromes, with more even distribution of genotypes. No over-represented phage genotypes were identified. Additionally, many bacteriophage genus-level clusters were found to be present in geographically isolated populations. Only a minor fraction of the phage contigs could be linked with the bacteriophage genomes. Our study indicates that bacteriophage ecological parameters in the intestinal ecosystems in horses and humans differ significantly, leading them to shape their corresponding viromes in different ways. Importance. (needed for mBio)The study presents the first in depth analysis of the composition and variability of the gut dsDNA bacteriophage community in the mammalian species, other than humans. The study demonstrates that the bacteriophage ecology in the gut is substantially different in different animal species. The results also indicate that the genetic diversity of the equine intestinal bacteriophages is immense and almost totally unexplored by the moment.

genomics↗

bioRxiv2019

Novel regulation from novel interactions: Identification of an RNA sponge that controls the levels, processing and efficacy of the RoxS riboregulator of central metabolism in Bacillus subtilis

Small RNAs (sRNAs) are a taxonomically-restricted but transcriptomically-abundant class of post-transcriptional regulators. While potentially of importance, we know the function of few. This is in no small part because we lack global-scale methodology enabling target identification, this being especially acute in species without known RNA meeting point proteins (e.g. Hfq). We apply a combination of psoralen RNA cross-linking and Illumina-sequencing to identify RNA-RNA interacting pairs in vivo in Bacillus subtilis, resolving previously well-described interactants. Although sRNA-sRNA pairings are rare (compared with sRNA/mRNA), we identify a robust example involving the unusually conserved sRNA (RoxS/RsaE) and an unstudied sRNA that we term Regulator of small RNA A (RosA). This interaction is found in independent samples across multiple conditions. Given the possibility of a novel associated regulatory mechanism, and the rarity of well-characterised bacterial sRNA-sRNA interactions, we mechanistically dissect RosA and its interactants. RosA we show to be a sponge RNA, the first to be described in a Gram-positive bacterium. RosA interacts with at least two sRNAs, RoxS and FsrA. Unexpectedly, it acts differently on each. As expected of a sponge RNA, FsrA is sequestered by RosA. The RosA/RoxS interaction is more complex affecting not only the level of RoxS but also its processing and efficacy. Importantly, RosA provides the condition-dependent intermediary between CcpA, the key regulator of carbon metabolism, and RoxS. This not only provides evidence for a novel, and functionally important, regulatory mechanism, but in addition, provides the missing link between transcriptional and post-transcriptional regulation of central metabolism.

microbiology↗

bioRxiv2018

Riding the wave of genomics, to investigate aquatic coliphage diversity and activity

Bacteriophages infecting Escherichia coli have been used as a proxy for faecal matter and water quality from a variety of environments. However, the diversity of coliphages that are present in seawater remains largely unknown, with previous studies largely focusing on morphological diversity. Here, we isolated and characterised coliphages from three coastal locations in the UK and Poland. This revealed a surprising genetic diversity, with comparative genomics and phylogenetic analysis of phage isolates facilitating the identification of putative new species within the genera RB69virus and T5virus and a putative new genus within the subfamily Tunavirinae. Furthermore, by combining this genomic data with proteomic and host range analyses a number of phage structural proteins were identified, one of which is likely to be responsible for the observed differences in host range.

microbiology↗