Biology subjects

Kingsley, R. A.

Publications and source records attributed to Kingsley, R. A..

14 recordsLinked to original sources

bioRxiv2025

SalmonAct Deciphers Transcription Factor Regulatory Activity in Salmonella Transcriptomics

Foodborne Salmonella enterica infection remains a major public health threat due to its prevalence in food, ease of transmission, and increasing antibiotic resistance. Consequently, understanding the molecular mechanisms underlying Salmonella pathogenesis is crucial for guiding novel diagnostic, preventative, and therapeutic approaches. High-throughput transcriptomic technologies are now often employed in Salmonella research to quantify how gene expression changes in response to various conditions or mutations. But due to the high dimensionality of this data, resulting from the comparison of the expression of thousands of genes from multiple strains or culture conditions with complex interactions, interpretation remains a demanding task. To address this issue, we present SalmonAct, a comprehensive signed and directed prior knowledge resource for inferring transcription factor activities in Salmonella. This new resource expands the toolkit available for Salmonella functional analysis. Built as an extension of the SalmoNet2 database, SalmonAct can be used to infer the activity of 191 transcription factors in 5991 regulatory interactions based on publicly available interaction and regulatory knockout data. SalmonAct enhances the interpretation of highly-dimensional transcriptomic data by identifying both highly influential and minimally active transcription factors that drive the observed expression state. SalmonAct aids in bridging the gap between model and non-model organisms functional analysis, and together with the SalmoNet2 resource, can be used for further downstream data analyses. ImportanceWhile modern high-throughput transcriptomics technologies provide effective ways of studying Salmonella enterica, the complexity of these datasets makes interpretation challenging. SalmonAct provides a new computational resource to connect gene expression changes with the activity of transcription factors, key regulators of bacterial adaptation and virulence. SalmonAct can help researchers progress from the analysis of gene expression profiles towards a clearer understanding of the regulatory programs driving the behaviour of the pathogen. By integrating prior knowledge of transcription factor - target gene relationships, SalmonAct contributes to uncovering novel mechanisms of bacterial pathogenesis, and supports the development of new approaches to combat Salmonella infections.

systems biology↗

bioRxiv2024

Reversible excision of the wzy locus in Salmonella Typhimurium may aid recovery following phage predation

Bacteriophage (phage) are promising novel antimicrobials but a key challenge to their effective implementation is the rapid emergence of phage resistance. An improved understanding of phage-host interactions is therefore needed. The Anderson phage typing scheme differentiates closely related strains of Salmonella enterica serovar Typhimurium (S. Typhimurium) based on sensitivity to a panel of phage preparations. Switches in phage type are indicative of changes in phage sensitivity and inform on the dynamics of phage interaction with their host bacteria. We investigated the molecular basis of switches between the relatively phage sensitive S. Typhimurium DT8 and phage resistant DT30 strains that are present in the same phylogenetic clade. DT30 strains emerged from DT8 strains predominantly by deletion of a genomic region affecting the wzy locus encoding an O-antigen polymerase. The deletion site was flanked by two perfect direct repeats designated attL and attR. During broth culture in the presence of a typing phage that used O-antigen as primary receptor the {Delta}wzy genotype increased in frequency compared with culture in the absence of phage and removal of attL prevented deletion of the wzy locus. Co-culture of S. Typhimurium DT8 with a strain lacking wzy resulted in reversion of the latter to wild type. We propose a model in which reversible deletion of the wzy locus enables recovery of S. Typhimurium DT8 following predation by phage that use O-antigen as their primary receptor. This was consistent with ancestral state reconstruction of DT8 and DT30 phylogeny that supported a model of reversible transition from DT8 to DT30 in natural populations. ImportanceS. Typhimurium is a major pathogen of livestock that adversely affects productivity and animal welfare and poses a risk of foodborne disease in the human population. Antibiotics are used to control Salmonella infections in livestock that contributes to the antimicrobial resistance global emergency. Viruses of bacteria (phage) are one alternative to antibiotics to control Salmonella in the food chain but their successful implementation as antimicrobials is restricted by the rapid emergence of resistance to phage. A better understanding of the outcome of phage-bacteria interactions is needed to optimise the design and implementation of phage-based antimicrobials. This study identifies a genetic mechanism that confers resistance to phage that use O-antigen as a receptor on the surface of Salmonella. The mechanism is likely to impart a fitness cost on the bacterium but importantly the mechanism has the potential to be revert to a fully fit state once phage predation ceases. A model for how the mechanism may contribute to survival and recovery following phage predation is proposed.

microbiology↗

bioRxiv2024

Genomic Epidemiology of SARS-CoV-2 in Norfolk, UK, March 2020 - December 2022

BackgroundIn the UK, the COVID-19 Genomics UK Consortium (COG-UK) established a real time national genomic surveillance system during the COVID-19 pandemic, producing centralised data for monitoring SARS-CoV-2. As a COG-UK partner, Quadram Institute Bioscience (QIB) in Norfolk sequenced over 87,000 SARS-CoV-2 genomes, contributing to the region becoming densely sequenced. Retrospective analysis of SARS-CoV-2 lineage dynamics in this region may contribute to preparedness for future pandemics. Methods29,406 SARS-CoV-2 whole genome sequences and corresponding metadata from Norfolk were extracted from the COG-UK dataset, sampled between March 2020 and December 2022, representing 9.9% of regional COVID-19 cases. Sequences were lineage typed using Pangolin, and subsequent lineage analysis carried out in R using RStudio and related packages, including graphical analysis using ggplot2. Results401 global lineages were identified, with 69.8% appearing more than once and 31.2% over ten times. Temporal clustering identified six lineage communities based on first lineage emergence. Alpha, Delta, and Omicron variants of concern (VOC) accounted for 8.6%, 34.9% and 48.5% of sequences respectively. These formed four regional epidemic waves alongside the remaining lineages which appeared in the early pandemic prior to VOC designation and were termed pre-VOC lineages. Regional comparison highlighted variability in VOC epidemic wave dates dependent on location. ConclusionThis study is the first to assess SARS-CoV-2 diversity in Norfolk across a large timescale within the COVID-19 pandemic. SARS-CoV-2 was both highly diverse and dynamic throughout the Norfolk region between March 2020 - December 2022, with a strong VOC presence within the latter two thirds of the study period. The study also displays the utility of incorporating genomic epidemiological methods into pandemic response. Data summaryThe COG-UK collection of SARS-CoV-2 sequences and metadata are available for public download on their archive website under the Latest sequence data heading . Sequence names for all sequences used from this dataset alongside GISAID accession numbers where present are available in Supplementary Table 1. Impact statementWe extracted 29,406 regional Norfolk based SARS-CoV-2 sequences from the COG-UK SARS-CoV-2 dataset and revealed significant regional diversity and dynamic emergence of variant of concern (VOC) epidemic waves - spanning Alpha, Delta and Omicron lineages. We also applied statistical modelling to complement genomic methodology, with temporal clustering of significant first lineage emergences chronologically matching VOC waves and subwaves. The study highlights the importance of integration of genomic epidemiology into public health strategies for pandemic response, and the utility of using this data for retrospective research.

genomics↗

bioRxiv2024

Low protein diet protects liver function upon Salmonella infection by metabolic reprogramming of macrophages

Background & AimsWestern diets are the underlying cause of metabolic and liver diseases. Recent trend to limit the consumption of protein-rich animal products has become more prominent. This dietary change entails decreased protein consumption; however, it is still unknown how this affects innate immunity. Here, we studied the influence of a low protein diet (LPD) on the liver response to bacterial infection. MethodsMice were fed a LPD and exposed to Salmonella enterica serotype Typhimurium infection. Mechanistic studies were done in vitro where bone marrow derived macrophages were cultured in a low-aa media to mimic in vivo reduction of protein availability and challenged with bacterial endotoxin. ResultsWe found that a LPD protects from S Typhimurium-induced liver damage. Bulk- and 10xsingle cell-RNA sequencing of liver tissues and isolated immune cells showed reduced activation of myeloid cells in mice fed with LPD after S Typhimurium infection. Mechanistically, we found reduced activation of the mammalian target of rapamycin (mTOR) pathway whilst increased phagocytosis and activation of autophagy in LPD-programmed macrophages. Dietary restoration of leucine reverted the protective effects of a LPD and restored the damaging effects of Salmonella on liver parenchyma in mice. ConclusionsLow protein diet protects the liver form S Typhimurium-induced tissue damage via modulating macrophage autophagy and phagocytosis. Our result support the causal role of dietary components on the fitness of the immune system. SYNOPSISLow protein diet protects the liver from Salmonella-mediated liver injury that associates with reduced mTOR activation and increased autophagy in macrophages. Restoration of the mTOR pathway with aminoacid supplementation reverses the protection of a low protein diet from Salmonella-liver damage.

immunology↗

bioRxiv2023

Collateral sensitivity increases the efficacy of a rationally designed bacteriophage combination to control Salmonella enterica

The ability of virulent bacteriophages to lyse bacteria influences bacterial evolution, fitness, and population structure. Knowledge of both host susceptibility and resistance factors is crucial for the successful application of bacteriophages as biological control agents in clinical therapy, food processing and agriculture. In this study, we isolated twelve bacteriophages termed SPLA phage which infect the foodborne pathogen Salmonella enterica. To determine phage host range, a diverse collection of Enterobacteriaceae and Salmonella enterica were used and genes involved in infection by six SPLA phages were identified using Salmonella Typhimurium strain ST4/74. Candidate host receptors included lipopolysaccharide, cellulose and BtuB. Lipopolysaccharide was identified as susceptibility factor for phage SPLA1a and mutations in LPS biosynthesis genes spontaneously emerged during culture with S. Typhimurium. Conversely, LPS was a resistance factor for phage SPLA5b that suggested that emergence of LPS mutations in culture with SPLA1a may represent a case of collateral sensitivity to SPLA5b. We show that combination therapy with SPLA1a and SPLA5b was more successful in limiting the emergence of phage resistance compared to monotherapy. Identification of host susceptibility and resistance genes and understanding infection dynamics is critical step in rationale design of phage cocktails against specific bacterial pathogens.

microbiology↗

bioRxiv2023

A hybrid and poly-polish workflow for the complete and accurate assembly of phage genomes: a case study of ten przondoviruses

Bacteriophages (phages) within the Przondovirus genus are T7-like podoviruses belonging to the Studiervirinae subfamily, within the Autographiviridae family and have a highly conserved genome organisation. The genome size of these phages ranges from 37 kb to 42 kb, encode 50-60 genes and are characterised by the presence of direct terminal repeats (DTRs) flanking the linear chromosome. These DTRs are often deleted during short-read-only and hybrid assemblies. Moreover, long-read-only assemblies are often littered with sequencing and/or assembly errors and require additional curation. Here, we present the isolation and characterisation of ten novel przondoviruses targeting Klebsiella spp. We describe HYPPA - a HYbrid and Poly-polish Phage Assembly workflow, which utilises long-read assemblies in combination with short-read sequencing to resolve phage DTRs and correcting errors, negating the need for laborious primer walking and Sanger sequencing validation. Our data demonstrate the importance of careful curation of phage assemblies before publication, and prior to using them for comparative genomics. IMPACT STATEMENTThe current workflows employed for phage genome assembly are often error-prone and can lead to many incomplete phage genomes being deposited within databases. This can create challenges when performing comparative genomics, and may also lead to incorrect taxonomic assignment. To overcome these challenges we proposed HYPPA, a workflow that can produce complete and high-quality phage genomes without the need for laborious lab-based validation. DATA SUMMARYPhage raw reads are available from the National Centre for Biotechnology Information Sequence Read Archive (NCBI-SRA) under the BioProject number PRJNA914245. Phage annotated genomes have been deposited at GenBank under the accessions OQ579023-OQ579032 (Table 1). Bacterial WGS data for clinical preterm infant samples have been deposited at GenBank under BioProject accession PRJNA471164 (Table S1). Bacterial raw reads for food samples are available from NCBI-SRA with individual accessions (SAMN33593347-SAMN33593351), and can be found under the BioProject number PRJNA941224 (Table S1). Strain-specific details for bacteria and publicly-available phages used in these analyses, along with accessions for the latter can be found in Table S1 and Table S6, respectively. The CL1-CL8 clinical Klebsiella strains (Table S1) were under a Materials Transfer Agreement, for which sequencing data and strain information is not available. O_TBL View this table: org.highwire.dtl.DTLVardef@8cae53org.highwire.dtl.DTLVardef@8e512org.highwire.dtl.DTLVardef@1f71a67org.highwire.dtl.DTLVardef@1e6947dorg.highwire.dtl.DTLVardef@11ebc58_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 1.C_FLOATNO O_TABLECAPTIONPrzondoviruses within the collection to date and data relating to the closest database relative. C_TABLECAPTION C_TBL

microbiology↗

bioRxiv2022

High-throughput transposon mutagenesis in the family Enterobacteriaceae reveals core essential genes and rapid turnover of essentiality

The Enterobacteriaceae are a scientifically and medically important clade of bacteria, containing the gut commensal and model organism Escherichia coli, as well as several major human pathogens including multiple serovars of Salmonella enterica and Klebsiella pneumoniae. Essential gene sets have been determined for several members of the Enterobacteriaceae, with the E. coli Keio single-gene deletion library often regarded as a gold standard for gene essentiality studies. However, it remains unclear how gene essentiality varies between related strains and species. To investigate this, we have assembled a collection of thirteen sequenced high-density transposon mutant libraries from five genera within the Enterobacteriaceae. We first benchmark a number of gene essentiality prediction approaches, investigate the effects of transposon density on essentiality prediction, and identify biases in transposon insertion sequencing data. Based on these investigations we develop a new classifier for gene essentiality. Using this new classifier, we define a core essential genome in the Enterobacteriaceae of 201 universally essential genes, and reconstruct an ancestral essential gene set of 296 genes. Despite the presence of a large cohort of variably essential genes, surprisingly we find an absence of evidence for genus-specific essential genes. A clear example of this sporadic essentiality is given by the set of genes regulating the {sigma}E extracytoplasmic stress response, which appears to have independently become essential multiple times in the Enterobacteriaceae. Finally, we compare our essential gene sets to the natural experiment of gene loss in obligate insect endosymbionts that have emerged from within the Enterobacteriaceae. This isolates a remarkably small set of genes absolutely required for survival, and uncovers several instances of essential stress responses masked by redundancy in free-living bacteria.

microbiology↗

bioRxiv2022

Strain and serovar variants of Salmonella enterica exhibit diverse tolerance to food chain-related stress

Non-Typhoidal Salmonella (NTS) continues to be a leading cause of foodborne illness worldwide. Food manufacturers implement hurdle technology by combining more than one approach to control food safety and quality, including preservatives such as organic acids, refrigeration, and heating. We assessed the variation in survival in stresses of genotypically diverse isolates of Salmonella enterica to identify genotypes with potential elevated risk to sub-optimal processing or cooking. Sub-lethal heat treatment, survival in desiccated conditions and growth in the presence of NaCl or organic acids were investigated. S. Gallinarum strain 287/91 was most sensitive to all stress conditions. While none of the strains replicated in a food matrix at 4{degrees}C, S. Infantis strain S1326/28 retained the greatest viability, and six strains exhibited a significantly reduced viability. A S. Kedougou strain exhibited the greatest resistance to incubation at 60{degrees}C in a food matrix that was significantly greater than S. Typhimurium U288, S Heidelberg, S. Kentucky, S. Schwarzengrund and S. Gallinarum strains. Two isolates of monophasic S. Typhimurium, S04698-09 and B54 Col9 exhibited the greatest tolerance to desiccation that was significantly more than for the S. Kentucky and S. Typhimurium U288 strains. In general, the presence of 12mM acetic acid or 14mM citric acid resulted in a similar pattern of decreased growth in broth, but this was not observed for S. Enteritidis, and S. Typhimurium strains ST4/74 and U288 S01960-05. Acetic acid had a moderately greater effect on growth despite the lower concentration tested. A similar pattern of decreased growth was observed in the presence of 6% NaCl, with the notable exception that S. Typhimurium strain U288 S01960-05 exhibited enhanced growth in elevated NaCl concentrations. An understanding of the molecular basis of phenotypic variation in response to stress has the potential to improve process validation during food challenge tests, improve processing, and result in more reliable risk assessments in the food industry.

microbiology↗

bioRxiv2022

Population structure and evolution of Salmonella enterica serotype Typhi in Zimbabwe before a typhoid conjugate vaccine immunization campaign

BackgroundThe continued emergence of Salmonella enterica serovar Typhi (S. Typhi) with ever increasing antimicrobial resistance (AMR), necessitates the use of vaccines in endemic countries. A typhoid fever outbreak in Harare, Zimbabwe in 2018 from a multidrug resistant S. Typhi with additional resistance to ciprofloxacin was the catalyst for the introduction of a typhoid conjugate vaccine program. To investigate the historic emergence and evolution of AMR of endemic S. Typhi in Zimbabwe and determined the population structure, gene flux and sequence polymorphisms of strains isolated prior to mass typhoid vaccination to provide a baseline for future evaluation of the effect of the vaccination program. MethodsWe determined the population structure, gene flux and sequence polymorphisms and reconstructed the evolution of AMR. The S. Typhi population structure was investigated in the context the genome sequence of 1904 strains isolated from 65 countries to reconstruct spread of endemic strains into Zimbabwe. FindingsThe population structure of S. Typhi in Zimbabwe is dominated by multidrug resistant genotype 4.3.1.1 (H58) that spread to Zimbabwe from neighboring countries around 2009. Evolution of AMR within Zimbabwe included acquisition of an IncN plasmid carrying a qnrS gene and a mutation in the quinolone resistance determining region of gyrA gene, both implicated in resistance to quinolone antibiotics. A minority population of antimicrobial susceptible S. Typhi genotype 3.3.1 strains was detected in typhoid cases. InterpretationThe currently dominant S. Typhi population is genotype 4.3.1.1 that spread to Zimbabwe and acquired additional AMR though acquisition of a plasmid and mutation of the gyrA gene. This study provides a baseline for future evaluation of the impact of the Typhoid Conjugate Vaccine program in Harare. FundingRAK and GT were supported by Bill and Melinda Gates Foundation project OPP1217121 and the BBSRC Institute Strategic Programme BB/R012504/1 and its constituent project BBS/E/F/000PR10348.

genomics↗

bioRxiv2021

Multi-layered networks of SalmoNet2 enable strain comparisons of the Salmonella genus on a molecular level

Serovars of the genus Salmonella primarily evolved as gastrointestinal pathogens in a wide range of hosts. Some serotypes later evolved further, adopting a more invasive lifestyle in a narrower host range associated with systemic infections. A system-level knowledge of these pathogens has the potential to identify the complex adaptations associated with the evolution of serovars with distinct pathogenicity, host range and risk to human health. This promises to aid the design of interventions and serve as a knowledge base in the Salmonella research community. Here we present SalmoNet2, a major update to SalmoNet, the first multi-layered interaction resource for Salmonella strains, containing protein-protein, transcriptional regulatory and enzyme enzyme interactions. The new version extends the number of Salmonella genomes from 11 to 20, including strains such as S. Typhimurium D23580, an epidemic multidrug-resistant strain leading to invasive non-typhoidal Salmonella Disease (iNTS), and a strain from Salmonella bongori, another species in the Salmonella genus. The database now uses strain specific metabolic models instead of a generalised model to highlight differences between strains. This has increased the coverage of high-quality protein-protein interactions, and enhances interoperability with other computational resources by adopting standardised formats. The resource website has been updated with tutorials to help researchers analyse their Salmonella data using molecular interaction networks from SalmoNet2. SalmoNet2 is accessible at http://salmonet.org/. ImportanceMulti-layered network databases collate information from multiple sources, and are powerful both as a knowledge base and platform for analysis. Here we present SalmoNet2, an integrated network resource of 20 Salmonella strains, containing protein-protein, transcriptional regulatory, and metabolic interactions. Key improvements to the update include expanding the number of strains, strain-specific metabolic networks, an increase in high quality protein-protein interactions, community standard computational formats to help interoperability, and online tutorials to help users analyse their data using SalmoNet2.

systems biology↗

bioRxiv2020

Ecological niche adaptation of a bacterial pathogen associated with reduced zoonotic potential

The emergence of new bacterial pathogens is a continuing challenge for agriculture and food safety. Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major cause of foodborne illness worldwide, with pigs a major zoonotic reservoir. Two variants, S. Typhimurium phage type U288 and monophasic S. Typhimurium (S. 4,[5],12:i:-) ST34 emerged and have accounted for the majority of isolates from pigs in the UK in the past two decades, but have distinct host range and risk to food safety. ST34 accounts for over 50% of all S. Typhimurium infections in people while U288 less than 2%. U288 and ST34 form distinct phylogenetic clusters within S. Typhimurium, defined by approximately 600 SNPs within their 5 Mbp genomes. Evolution of the U288 clade from an LT2-like ancestor was characterised by the acquisition of AMR genes, insertions and deletions in the virulence plasmid pU288-1, and the accumulation of polymorphisms, some of which resulted in truncation of coding sequences. U288 isolates exhibited lower growth rate and viability following desiccation compared to ST34 isolates, characteristics that could affect transmission through the food chain. U288 and ST34 isolates exhibited distinct outcomes of infection in the murine model of colitis, and colonised pigs in a manner that affected the disease symptoms and distribution in organs. U288 infection was more disseminated in the lymph nodes while ST34 were recovered in greater numbers in the intestinal contents. These data are consistent with the evolution of S. Typhimurium U288 adaptation to pigs that may determine their reduced zoonotic potential. ImportanceBacterial pathogens continually evolve to exploit new ecological niches as they emerge due to human activity including agricultural, medical or societal practice. The consequences of the emergence of new pathogens may affect outcome of infection and risk to human or animal health. Genome sequence can resolve the population structure, identify variants that are evolving as they enter a new niche, and pinpoint potential functional divergence. We report a variant S. Typhimurium that adapted to a unique niche distinct to that occupied by a second S. Typhimurium variant circulating in the same pig populations. Adaptation was accompanied by phenotypic and genotypic changes consistent with a more invasive lifestyle and a decreased zoonotic potential observed in the epidemiological record. Our findings suggest that pathogen genotypic variation may be useful in estimating zoonotic potential and threat to livestock welfare.

microbiology↗

bioRxiv2020

Bacterial single-cell genomics enables phylogenetic analysis of in vitro evolutionary studies

Single-cell DNA sequencing has the potential to reveal detailed hierarchical structures in evolving populations of cells. Single cell approaches are increasingly used to study clonal evolution in human ageing and cancer, but have not yet been deployed to study evolving microbial populations. Here, we present an approach for single bacterial genomic analysis using FACS isolation of individual bacteria followed by whole-genome amplification and sequencing. We apply this to in vitro experimental evolution of a hypermutator strain of Salmonella in response to antibiotic stress (ciprofloxacin). By analysing sequence polymorphisms in individual cells from the population we identified the presence and prevalence of sub-populations which have acquired polymorphisms in genes previously demonstrated to be associated with ciprofloxacin susceptibility. We were also able to identify that the population exposed to antibiotic stress was able to both develop resistance whilst maintaining diversity. This population structure could not be resolved from bulk sequence data, and our results show how high-throughput single-cell sequencing can enhance experimental studies of bacterial evolution.

genomics↗

bioRxiv2019

Evolution of Salmonella enterica serotype Typhimurium driven by anthropogenic selection and niche adaptation

Salmonella enterica serotype Typhimurium (S. Typhimurium) is a leading cause of gastroenteritis and disseminated disease worldwide. Two S. Typhimurium strains (SL1344 and ATCC14028) are widely used to study host-pathogen interactions, yet genotypic variation results in strains with diverse host range, pathogenicity and risk to food safety. A robust fully parsimonious phylogenetic tree constructed from recombination purged variation in the whole genome sequence of 131 diverse strains of S. Typhimurium revealed population structure composed of two high order clades ( and {beta}) and multiple subclades on extended internal branches, that exhibited distinct signatures of host adaptation and anthropogenic selection. Clade contained a number of subclades composed of strains from well characterized epidemics in domesticated animals, while clade {beta} predominantly contained subclades associated with wild avian species, with the notable exception of a subclade containing the DT204/49 complex. The contrasting epidemiology of and {beta} strains was reflected in a distinct distribution of antimicrobial resistance (AMR) genes, accumulation of hypothetically disrupted coding sequences (HDCS), and signatures of functional diversification associated with invasiveness of host adapted serotypes. Gene flux was predominantly driven by acquisition, loss or recombination of prophage. The acquisition of large genetic islands (SGI-1 and 4) was limited to two recent pandemic clones (DT104 and monophasic S. Typhimurium ST34) in clade . Together, our data are consistent with the view that a broad host range common ancestor of S. Typhimurium diversified with clade lineages remained largely associated with multiple domesticated animal species, while clade {beta} spawned multiple lineages that underwent diversifying selection associated with adaptation to various niches, predominantly in wild avian species.

genomics↗

bioRxiv2018

Adding function to the genome of African Salmonella ST313

Salmonella Typhimurium ST313 causes invasive nontyphoidal Salmonella (iNTS) disease in sub-Saharan Africa, targeting susceptible HIV+, malarial or malnourished individuals. An in-depth genomic comparison between the ST313 isolate D23580, and the well-characterized ST19 isolate 4/74 that causes gastroenteritis across the globe, revealed extensive synteny. To understand how the 856 nucleotide variations generated phenotypic differences, we devised a large-scale experimental approach that involved the global gene expression analysis of strains D23580 and 4/74 grown in sixteen infection-relevant growth conditions. Comparison of transcriptional patterns identified virulence and metabolic genes that were differentially expressed between D23580 versus 4/74, many of which were validated by proteomics. We also uncovered the S. Typhimurium D23580 and 4/74 genes that showed expression differences during infection of murine macrophages. Our comparative transcriptomic data are presented in a new enhanced version of the Salmonella expression compendium SalComD23580: bioinf.gen.tcd.ie/cgi-bin/salcom_v2.pl. We discovered that the ablation of melibiose utilization was caused by 3 independent SNP mutations in D23580 that are shared across ST313 lineage 2, suggesting that the ability to catabolise this carbon source has been negatively selected during ST313 evolution. The data revealed a novel plasmid maintenance system involving a plasmid-encoded CysS cysteinyl-tRNA synthetase, highlighting the power of large-scale comparative multi-condition analyses to pinpoint key phenotypic differences between bacterial pathovariants.

microbiology↗