scholarly journals Pneumococcal Colonization and Virulence Factors Identified Via Experimental Evolution in Infection Models

2021 ◽  
Author(s):  
Angharad E Green ◽  
Deborah Howarth ◽  
Chrispin Chaguza ◽  
Haley Echlin ◽  
R Frèdi Langendonk ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Parallel Evolution ◽  
Experimental System ◽  
Serial Passage ◽  
Invasive Disease ◽  
Vaccine Antigen ◽  
Nasopharyngeal Carriage ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Infection Models

Abstract Streptococcus pneumoniae is a commensal of the human nasopharynx and a major cause of respiratory and invasive disease. We examined adaptation and evolution of pneumococcus, within nasopharynx and lungs, in an experimental system where the selective pressures associated with transmission were removed. This was achieved by serial passage of pneumococci, separately, in mouse models of nasopharyngeal carriage or pneumonia. Passaged pneumococci became more effective colonizers of the respiratory tract and we observed several examples of potential parallel evolution. The cell wall-modifying glycosyltransferase LafA was under strong selection during lung passage, whereas the surface expressed pneumococcal vaccine antigen gene pvaA and the glycerol-3-phosphate dehydrogenase gene gpsA were frequent targets of mutation in nasopharynx-passaged pneumococci. These mutations were not identified in pneumococci that were separately evolved by serial passage on laboratory agar. We focused on gpsA, in which the same single nucleotide polymorphism arose in two independently evolved nasopharynx-passaged lineages. We describe a new role for this gene in nasopharyngeal carriage and show that the identified single nucleotide change confers resistance to oxidative stress and enhanced nasopharyngeal colonization potential. We demonstrate that polymorphisms in gpsA arise and are retained during human colonization. These findings highlight how within-host environmental conditions can determine trajectories of bacterial evolution. Relative invasiveness or attack rate of pneumococcal lineages may be defined by genes that make niche-specific contributions to bacterial fitness. Experimental evolution in animal infection models is a powerful tool to investigate the relative roles played by pathogen virulence and colonization factors within different host niches.

scholarly journals Identification of colonisation and virulence determinants of Streptococcus pneumoniae via experimental evolution in mouse infection models

2020 ◽  
Author(s):  
Angharad E Green ◽  
Deborah Howarth ◽  
Chrispin Chaguza ◽  
Haley Echlin ◽  
R Frèdi Langendonk ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Experimental Evolution ◽  
Parallel Evolution ◽  
Serial Passage ◽  
Invasive Disease ◽  
Virulence Determinants ◽  
Upper Respiratory Tract ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Infection Models

AbstractStreptococcus pneumoniae is a commensal of the human nasopharynx and a major cause of respiratory and invasive disease. Pneumococcus stimulates upper respiratory tract inflammation that promotes shedding from mucosal surfaces and transmission to new hosts. Colonisation and transmission are partially antagonistic processes. Adhesion to surfaces and evasion of host responses favours the former, whilst detachment, promoted by inflammation, is necessary for the latter. We sought to determine how adaptation and evolution of pneumococcus within its nasopharyngeal niche might progress when selective pressures associated with transmission were removed. This was achieved by serial passage of pneumococci in mouse models of nasopharyngeal carriage, manually transferring bacteria between mice. To assess the role of host environmental factors on pneumococcal evolution, we also performed analogous experimental evolution in a mouse pneumonia model, passaging pneumococci through lungs. Nasopharynx-passaged pneumococci became more effective colonisers, whilst those evolved within lungs showed reduced virulence. We observed selection of mutations in genes associated with cell wall biogenesis and metabolism in both nasopharynx and lung lineages, but identified prominent examples of parallel evolution that were niche specific. We focussed on gpsA, a gene in which the same single nucleotide polymorphism arose in two independently evolved nasopharynx-passaged lineages. We identified a single nucleotide change conferring resistance to oxidative stress and enhanced nasopharyngeal colonisation potential. We show that gpsA is also a frequent target of mutation during human colonisation. These findings highlight the role played by the host environment in determining trajectories of bacterial evolution and the potential of experimental evolution in animal infection models for identification of novel pathogen virulence and colonisation factors.

scholarly journals The Underlying Structure of Adaptation under Strong Selection in 12 Experimental Yeast Populations

2014 ◽  
Vol 13 (9) ◽  
pp. 1200-1206 ◽  
Author(s):  
Linda M. Kohn ◽  
James B. Anderson
Keyword(s):  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Experimental Evolution ◽  
Parallel Evolution ◽  
High Salt ◽  
The Other ◽  
Underlying Structure ◽  
Single Nucleotide ◽  
Strong Selection ◽  
Low Glucose

ABSTRACTThe aims of this study were to determine (i) whether adaptation under strong selection occurred through mutations in a narrow target of one or a few nucleotide sites or a broad target of numerous sites and (ii) whether the programs of adaptation previously observed from three experimental populations were unique or shared among populations that underwent parallel evolution. We used archived population samples from a previous study, representing 500 generations of experimental evolution in 12 populations under strong selection, 6 populations in a high-salt environment and 6 populations in a low-glucose environment. Each set of six populations included four with sexual reproduction and two with exclusively asexual reproduction. Populations were sampled as resequenced genomes of 115 individuals and as bulk samples from which frequencies of mutant alleles were estimated. In a high-salt environment, a broad target of 11 mutations within the proton exporter,PMA1, was observed among the six populations, in addition to expansions of theENAgene cluster. This pattern was shared among populations that underwent parallel evolution. In a low-glucose environment, two programs of adaptation were observed. The originally observed pattern of mutation inMDS3/MKT1in population M8 was a narrow target of a single nucleotide, unique to this population. Among the other five populations, the three mutations were shared in a broad target, sensing/signaling genesRAS1andRAS2. RAS1/RAS2mutations were not observed in the high-salt populations;PMA1mutations were observed only in a high-salt environment.

scholarly journals Impact of a Single Nucleotide Change or Non-Nucleoside Modifications in G-Rich Region on the Quadruplex–Duplex Hybrid Formation

Biomolecules ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1236
Author(s):  
Dorota Gudanis ◽  
Karolina Zielińska ◽  
Daniel Baranowski ◽  
Ryszard Kierzek ◽  
Piotr Kozłowski ◽  
...  
Keyword(s):  
Target Sequence ◽  
Rich Region ◽  
Rna Sequences ◽  
Single Nucleotide ◽  
Alternative Structures ◽  
Single Nucleotide Change ◽  
G Quadruplex ◽  
Quadruplex Formation ◽  
Target Rna ◽  
Insight Into

In this paper, a method to discriminate between two target RNA sequences that differ by one nucleotide only is presented. The method relies on the formation of alternative structures, i.e., quadruplex–duplex hybrid (QDH) and duplex with dangling ends (Dss), after hybridization of DNA or RNA G-rich oligonucleotides with target sequences containing 5′–GGGCUGG–3′ or 5′–GGGCGGG–3′ fragments. Using biophysical methods, we studied the effect of oligonucleotide types (DNA, RNA), non-nucleotide modifications (aliphatic linkers or abasic), and covalently attached G4 ligand on the ability of G-rich oligonucleotides to assemble a G-quadruplex motif. We demonstrated that all examined non-nucleotide modifications could mimic the external loops in the G-quadruplex domain of QDH structures without affecting their stability. Additionally, some modifications, in particular the presence of two abasic residues in the G-rich oligonucleotide, can induce the formation of non-canonical QDH instead of the Dss structure upon hybridization to a target sequence containing the GGGCUGG motif. Our results offer new insight into the sequential requirements for the formation of G-quadruplexes and provide important data on the effects of non-nucleotide modifications on G-quadruplex formation.

scholarly journals Combining metabolomics and experimental evolution reveals key mechanisms underlying longevity differences in laboratory evolved Drosophila melanogaster populations

2021 ◽  
Author(s):  
Mark Phillips ◽  
Kenneth R. Arnold ◽  
Zer Vue ◽  
Heather Beasley ◽  
Edgar Garza Lopez ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Carbohydrate Metabolism ◽  
Experimental Evolution ◽  
Statistical Power ◽  
Accelerated Aging ◽  
Experimental System ◽  
Tca Cycle ◽  
Dna And Rna ◽  
Metabolomic Data ◽  
Genetic Mechanisms

Experimental evolution with Drosophila melanogaster has been used extensively for decades to study aging and longevity. In recent years, the addition of DNA and RNA sequencing to this framework has allowed researchers to leverage the statistical power inherent to experimental evolution study the genetic basis of longevity itself. Here we incorporated metabolomic data into to this framework to generate even deeper insights into the physiological and genetic mechanisms underlying longevity differences in three groups of experimentally evolved D. melanogaster populations with different aging and longevity patterns. Our metabolomic analysis found that aging alters mitochondrial metabolism through increased consumption of NAD+ and increased usage of the TCA cycle. Combining our genomic and metabolomic data produced a list of biologically relevant candidate genes. Among these candidates, we found significant enrichment for genes and pathways associated with neurological development and function, and carbohydrate metabolism. While we do not explicitly find enrichment for aging canonical genes, neurological dysregulation and carbohydrate metabolism are both known to be associated with accelerated aging and reduced longevity. Taken together, our results in total provide very plausible genetic mechanisms for what might be driving longevity differences in this experimental system. More broadly, our findings demonstrate the value of combining multiple types of omic data with experimental evolution when attempting to dissect mechanisms underlying complex and highly polygenic traits like aging.

scholarly journals Altered Utilization of N-Acetyl-d-Galactosamine by Escherichia coli O157:H7 from the 2006 Spinach Outbreak

2007 ◽  
Vol 190 (5) ◽  
pp. 1710-1717 ◽  
Author(s):  
Amit Mukherjee ◽  
Mark K. Mammel ◽  
J. Eugene LeClerc ◽  
Thomas A. Cebula
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Culture Collection ◽  
Base Substitution ◽  
Phosphotransferase System ◽  
Single Nucleotide ◽  
E Coli ◽  
Single Nucleotide Change ◽  
Phenotype Comparison ◽  
In Silico Analyses

ABSTRACT In silico analyses of previously sequenced strains of Escherichia coli O157:H7, EDL933 and Sakai, localized the gene cluster for the utilization of N-acetyl-d-galactosamine (Aga) and d-galactosamine (Gam). This gene cluster encodes the Aga phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) and other catabolic enzymes responsible for transport and catabolism of Aga. As the complete coding sequences for enzyme IIA (EIIA)Aga/Gam, EIIBAga, EIICAga, and EIIDAga of the Aga PTS are present, E. coli O157:H7 strains normally are able to utilize Aga as a sole carbon source. The Gam PTS complex, in contrast, lacks EIICGam, and consequently, E. coli O157:H7 strains cannot utilize Gam. Phenotypic analyses of 120 independent isolates of E. coli O157:H7 from our culture collection revealed that the overwhelming majority (118/120) displayed the expected Aga+ Gam− phenotype. Yet, when 194 individual isolates, derived from a 2006 spinach-associated E. coli O157:H7 outbreak, were analyzed, all (194/194) displayed an Aga− Gam− phenotype. Comparison of aga/gam sequences from two spinach isolates with those of EDL933 and Sakai revealed a single nucleotide change (G:C→A:T) in the agaF gene in the spinach-associated isolates. The base substitution in agaF, which encodes EIIAAga/Gam of the PTS, changes a conserved glycine residue to serine (Gly91Ser). Pyrosequencing of this region showed that all spinach-associated E. coli O157:H7 isolates harbored this same G:C→A:T substitution. Notably, when agaF + was cloned into an expression vector and transformed into six spinach isolates, all (6/6) were able to grow on Aga, thus demonstrating that the Gly91Ser substitution underlies the Aga− phenotype in these isolates.

scholarly journals LB1. Regional Assessment and Containment of Candida auris Transmission in Post-Acute Care Settings—Orange County, California, 2019

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S993-S993 ◽  
Author(s):  
Ellora Karmarkar ◽  
Ellora Karmarkar ◽  
Kathleen O’Donnell ◽  
Christopher Prestel ◽  
Kaitlin Forsberg ◽  
...  
Keyword(s):  
Acute Care ◽  
Orange County ◽  
Invasive Disease ◽  
Nucleotide Polymorphisms ◽  
Nursing Facilities ◽  
Candida Auris ◽  
Single Nucleotide ◽  
Skilled Nursing ◽  
And Control

Abstract Background Patients in long-term acute care hospitals (LTACHs) and skilled nursing facilities with ventilator units (VSNFs) are at high risk for Candida auris colonization; among patients colonized with this emerging pathogen, 5%–10% develop invasive disease with >45% mortality. In September 2018, a California LTACH-affiliated laboratory began enhanced C. auris surveillance by classifying species of Candida isolated from routine urine specimens. In February 2019, the first known Southern California case was detected in an Orange County (OC) LTACH; the patient had not traveled outside the region, indicating local acquisition. We performed point prevalence surveys (PPS) and infection prevention (IP) assessments at all OC LTACHs and VSNF subacute units to identify patients colonized with C. auris and control transmission. Methods During March–August 2019, we conducted PPS at facilities by collecting composite axilla and groin swabs for C. auris polymerase chain reaction testing and reflex culture from all patients who assented. Facilities with ≥1 C. auris-colonized patient repeated a PPS every 2 weeks to assess for new transmission. Isolate relatedness was assessed by whole-genome sequencing (WGS). We evaluated hand hygiene (HH) adherence, access to alcohol-based hand rubs (ABHR), and cleaning of high-touch surfaces to guide IP recommendations. Results The first PPS at all OC LTACHs (n = 3) and adult VSNFs (n = 14) identified 45 C. auris-colonized patients in 3 (100%) LTACHs and 6 (43%) VSNFs; after repeated PPS, the total count reached 124. Most patients (70%) were at 2 facilities (Table 1). Three of 124 patients developed candidemia. To date, isolates from 48 patients have completed WGS; all were highly related (<11 single-nucleotide polymorphisms) in the African clade. Of 9 facilities with C. auris, 5 had HH adherence < 50%, 3 had limited ABHR, and at 2, <60% of assessed high-touch surfaces were clean. We recommended regular HH and cleaning audits, and increased ABHR. Conclusion Our investigation, prompted by enhanced surveillance, identified C. auris at 9 OC facilities. WGS indicated a single introduction and local transmission. Early detection, followed by rapid county-wide investigation and IP support, enabled containment efforts for C. auris in OC. Disclosures All authors: No reported disclosures.

scholarly journals Molecular basis for the human erythrocyte glycophorin specifying the Miltenberger class I (MiI) phenotype

Blood ◽  
1992 ◽  
Vol 80 (1) ◽  
pp. 257-263 ◽  
Author(s):  
CH Huang ◽  
P Spruell ◽  
JJ Moulds ◽  
OO Blumenfeld
Keyword(s):  
Molecular Basis ◽  
Consensus Sequence ◽  
Direct Repeat ◽  
Single Copy ◽  
Class I ◽  
Blood Group System ◽  
White Family ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Polymerase Chain

Abstract Human glycophorin Mil (HGpMil) is a structural variant of the MNSs blood group system that specifies the Miltenberger class I phenotype. We report here the molecular basis of the HGpMil gene identified in a white family in which the first homozygote was encountered. Immunoblotting analysis showed the expression of HGpMil and HGpB but the absence of HGpA on the homozygous Mil erythrocytes. Southern blot analysis detected no gross alterations in gene structure or band intensity. Genomic sequences encompassing exons II and III of the HGpMil gene were amplified by single-copy polymerase chain reaction. Restriction digestion and direct DNA sequence analysis showed that HGpMil gene is derived from an alpha N allele of HGpA and differs from the latter in the third exon by a single nucleotide change. In HGpMil, the presence of a deoxythymidine at the second position of codon 28 (ATG) not only resulted in a methionine substitution but also altered the consensus sequence for N-glycosylation from Asn-Asp-Thr to Asn-Asp- Met. These data are consistent with the occurrence of Mil on the red blood cell membrane as a variant deficient in the asparagine-linked carbohydrate unit. Significantly, this particular point mutation lies in between the two half-sites of a direct repeat that has been implicated to facilitate the recombination events leading to several other glycophorin genes of the Miltenberger series. Based on this relatedness, we propose an untemplated nucleotide replacement resulting from a gene conversion event as the molecular basis for the origin of HGpMil gene.

Novel single-nucleotide change inGYP*Ain a person who made an alloantibody to a new high-prevalence MNS antigen called ENEV

Transfusion ◽  
2010 ◽  
Vol 50 (4) ◽  
pp. 856-860 ◽  
Author(s):  
Randall W. Velliquette ◽  
Zong Hu ◽  
Christine Lomas-Francis ◽  
Kim Hue-Roye ◽  
Jean L. Allen ◽  
...  
Keyword(s):  
Nucleotide Change ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
High Prevalence

A comparison of sequence-based polymorphism and haplotype content in transcribed and anonymous regions of the barley genome

Genome ◽  
2004 ◽  
Vol 47 (2) ◽  
pp. 389-398 ◽  
Author(s):  
Joanne Russell ◽  
Allan Booth ◽  
John Fuller ◽  
Brian Harrower ◽  
Peter Hedley ◽  
...  
Keyword(s):  
Nucleotide Diversity ◽  
Wild Barley ◽  
Genomic Ssrs ◽  
Dna Polymorphisms ◽  
Nucleotide Polymorphisms ◽  
Nucleotide Change ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Haplotype Data ◽  
Fertile Crescent

Direct estimates of sequence diversity provides an abundant source of DNA polymorphisms based on single nucleotide polymorphisms (SNPs). The frequency and distribution of nucleotide diversity within 23 genes associated with grain germination in barley were determined in a sample of accessions representing European cultivars, landraces, and wild barley accessions from throughout the fertile crescent. The overall nucleotide diversity ranged from 0.0021 to 0.0189 with a single nucleotide change being detected every 78 bp and insertion–deletion events being observed every 680 bp. Within the cultivated (H. vulgare) genepool, a small number of haplotypes were detected, the total number of haplotypes observed in H. spontaneum was almost double that detected in H. vulgare (46 and 26, respectively). Distinct haplotypes were observed in the H. spontaneum and landrace genepools, which are highly divergent from H. vulgare. A comparison of SNP-based haplotype data with EST-derived SSRs and genomic SSRs revealed a similar trend of decreasing variability in the cultivated genepool. However, the number of unique alleles identified in the cultivated sample was much greater with genomic SSRs (18%) compared with only 2.1% for SNPs and 3.8% for EST-derived SSRs. The potential utility of SNPs and EST-derived SSRs for association mapping in barley is discussed.Key words: SNPs, haplotype, SSRs, barley.

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