scholarly journals Balance between promiscuity and specificity in phage λ host range

2020 ◽  
Author(s):  
Bryan Andrews ◽  
Stanley Fields
Keyword(s):  
Host Range ◽  
Host Resistance ◽  
Fitness Landscape ◽  
Tail Fiber ◽  
Wild Type ◽  
E Coli ◽  
General Ability ◽  
Novel Host ◽  
Selection For ◽  
Resistance To Viruses

AbstractAs hosts acquire resistance to viruses, viruses must overcome that resistance to re-establish infectivity, or go extinct. Despite the significant hurdles associated with adapting to a resistant host, viruses are evolutionarily successful and maintain stable coevolutionary relationships with their hosts. To investigate the factors underlying how pathogens adapt to their hosts, we performed a deep mutational scan of the region of the λ tail fiber tip protein that mediates contact with the λ host, E. coli. Phages harboring amino acid substitutions were subjected to selection for infectivity on wild type E. coli, revealing a highly restrictive fitness landscape, in which most substitutions completely abrogate function. By comparing this lack of mutational tolerance to evolutionary diversity, we highlight a set of mutationally intolerant and diverse positions associated with host range expansion. Imposing selection for infectivity on three λ-resistant hosts, each harboring a different missense mutation in the λ receptor, reveals hundreds of adaptive variants in λ. We distinguish λ variants that confer promiscuity, a general ability to overcome host resistance, from those that drive host-specific infectivity. Both processes may be important in driving adaptation to a novel host.

scholarly journals REGULATION OF NEWLY EVOLVED ENZYMES. III EVOLUTION OF THE ebg REPRESSOR DURING SELECTION FOR ENHANCED LACTASE ACTIVITY

Genetics ◽  
1977 ◽  
Vol 85 (2) ◽  
pp. 193-201
Author(s):  
Barry G Hall ◽  
Norma D Clarke
Keyword(s):  
Regulatory Gene ◽  
Enzyme Synthesis ◽  
Lactase Activity ◽  
Wild Type ◽  
Regulatory Mutation ◽  
E Coli ◽  
Lactose Induction ◽  
A Cell ◽  
Lactose Utilization ◽  
Selection For

ABSTRACT The evolution of lactose utilization by lacZ deletion strains of E. coli occurs via mutations in the ebg genes. We show that one kind of mutation in the regulatory gene ebgR results in a repressor which retains the ability to repress synthesis of ebg enzymes, but which permits 4.5-fold more ebg enzyme synthesis during lactose induction than does the wild-type repressor. A comparison between the growth rate of various ebg  + strains on lactose and the amount of ebg enzyme synthesized by these strains shows that the rate of enzyme synthesis permitted by the wild-type repressor is insufficient for growth on lactose as a sole carbon source by a cell with the most active ebg lactase yet isolated. We conclude, therefore, that the evolution of lactose utilization requires both a structural and a regulatory mutation.

scholarly journals A Tail Fiber Protein and a Receptor-Binding Protein Mediate ICP2 Bacteriophage Interactions with Vibrio cholerae OmpU

2021 ◽  
Author(s):  
Andrea N.W. Lim ◽  
Minmin Yen ◽  
Kimberley D. Seed ◽  
David W. Lazinski ◽  
Andrew Camilli
Keyword(s):  
Host Range ◽  
Vibrio Cholerae ◽  
Receptor Binding ◽  
Mutant Phenotype ◽  
Tail Fiber ◽  
Missense Mutations ◽  
Wild Type ◽  
Mutant Strains ◽  
Stool Samples ◽  
Receptor Binding Protein

ICP2 is a virulent bacteriophage (phage) that preys on Vibrio cholerae. ICP2 was first isolated from cholera patient stool samples. Some of these stools also contained ICP2-resistant isogenic V. cholerae strains harboring missense mutations in the trimeric outer membrane porin protein OmpU, identifying it as the ICP2 receptor. In this study, we identify the ICP2 proteins that mediate interactions with OmpU by selecting for ICP2 host-range mutants within infant rabbits infected with a mixture of wild type and OmpU mutant strains. ICP2 host-range mutants, that can now infect OmpU mutant strains, had missense mutations in putative tail fiber gene gp25 and putative adhesin gp23. Using site-specific mutagenesis we show that single or double mutations in gp25 are sufficient to generate the host-range mutant phenotype. However, at least one additional mutation in gp23 is required for robust plaque formation on specific OmpU mutants. Mutations in gp23 alone were insufficient to give a host-range mutant phenotype. All ICP2 host-range mutants retained the ability to plaque on wild type V. cholerae cells. The strength of binding of host-range mutants to V. cholerae correlated with plaque morphology, indicating that the selected mutations in gp25 and gp23 restore molecular interactions with the receptor. We propose that ICP2 host-range mutants evolve by a two-step process where, first, gp25 mutations are selected for their broad host-range, albeit accompanied by low level phage adsorption. Subsequent selection occurs for gp23 mutations that further increase productive binding to specific OmpU alleles, allowing for near wild type efficiencies of adsorption and subsequent phage multiplication. Importance Concern over multidrug-resistant bacterial pathogens, including Vibrio cholerae, has led to a renewed interest in phage biology and their potential for phage therapy. ICP2 is a genetically unique virulent phage isolated from cholera patient stool samples. It is also one of three phages in a prophylactic cocktail shown to be effective in animal models of infection and the only one of the three that requires a protein receptor (OmpU). This study identifies an ICP2 tail fiber and a receptor binding protein and examines how ICP2 responds to the selective pressures of phage-resistant OmpU mutants. We found that this particular co-evolutionary arms race presents fitness costs to both ICP2 and V. cholerae.

ucFabV Requires Functional Reductase Activity to Confer Reduced Triclosan Susceptibility in Escherichia coli

2015 ◽  
Vol 25 (6) ◽  
pp. 394-402 ◽  
Author(s):  
Taylor L. Fischer ◽  
Robert J. White ◽  
Katherine F.K. Mares ◽  
Devin E. Molnau ◽  
Justin J. Donato
Keyword(s):  
Escherichia Coli ◽  
Reductase Activity ◽  
Acid Synthesis ◽  
Temperature Sensitive ◽  
Wild Type ◽  
E Coli ◽  
Enoyl Acp Reductase ◽  
Selection For

<b><i>Background/Aims:</i></b> We previously identified the Triclo1 fosmid in a functional metagenomic selection for clones that increased triclosan tolerance in <i>Escherichia coli</i>. The active enzyme encoded by Triclo1 is ucFabV. Although ucFabV is homologous to FabV from other organisms, ucFabV contains substitutions at key positions that would predict differences in substrate binding. Therefore, a detailed characterization of ucFabV was conducted to link its biochemical activity to its ability to confer reduced triclosan sensitivity. <b><i>Methods:</i></b> ucFabV and a catalytic mutant were purified and used to reduce crotonoyl-CoA in vitro. The mutant and wild-type enzymes were introduced into <i>E. coli</i>, and their ability to confer triclosan tolerance as well as suppress a temperature-sensitive mutant of FabI were measured. <b><i>Results:</i></b> Purified ucFabV, but not the mutant, reduced crotonoyl-CoA in vitro. The wild-type enzyme confers increased triclosan tolerance when introduced into <i>E. coli</i>, whereas the mutant remained susceptible to triclosan<i>. </i>Additionally, wild-type ucFabV, but not the mutant, functionally replaced FabI within living cells. <b><i>Conclusion:</i></b> ucFabV confers increased tolerance through its function as an enoyl-ACP reductase. Furthermore, ucFabV is capable of restoring viability in the presence of compromised FabI, suggesting ucFabV is likely facilitating an alternate step within fatty acid synthesis, bypassing FabI inhibition.

Zur Frage des Zeitpunktes der Entscheidung zwischen abortivem oder rekombinativem Verhalten eines transduzierten Chromosomenfragmentes in der Empfängerzelle

1965 ◽  
Vol 20 (4) ◽  
pp. 284-289
Author(s):  
F. Kaudewitz ◽  
H. Schmieger
Keyword(s):  
Donor Cell ◽  
Cell Populations ◽  
Linkage Data ◽  
Wild Type ◽  
Isolated Cells ◽  
Auxotrophic Strain ◽  
Chromosomal Fragment ◽  
E Coli ◽  
Selection For ◽  
Arabinose Fermentation

In wild-type transduction of auxotrophic strain E. coli B/r/thr-1/leu-1/ara-12 colonies auxotrophic for leucine or threonine do not all arise at the same time after plating. In such crosses 48 hrs. after plating from about 20% of minute colonies grown from single abortively transduced cells there can be isolated cells capable to form genetically stable colonies prototrophic for leucine or threonine. Turbidity-measurements on cell populations derived from isolated minute colonies prove that such leu+-cells arise on the plate up to at least 96 hrs. after transduction. Linkage-data of the sites leu+-1 or thr+-1 with ara-12 for these cells disprove the occurence of the thr+ or leu+-state by backmutation. Transduction with E. coli B/r/ara-5 as donor with selection for arabinose-fermentation demonstrates the failure of delayed arising leu+ or thr+-cells in crosses yielding no minute colonies caused by abortive transduction. The experiments are discussed as evidence for the occurence of recombination between the acceptor-chromosome and the abortively transduced chromosomal fragment of a donor cell within a minute colony many cell generations after injection of this fragment.

scholarly journals Existing Host Range Mutations Constrain Further Emergence of RNA Viruses

2018 ◽  
Vol 93 (4) ◽  
Author(s):  
Lele Zhao ◽  
Mansha Seth-Pasricha ◽  
Dragoş Stemate ◽  
Alvin Crespo-Bellido ◽  
Jacqueline Gagnon ◽  
...  
Keyword(s):  
Host Range ◽  
Range Expansion ◽  
Rna Viruses ◽  
Point Mutations ◽  
Model System ◽  
The Novel ◽  
Wild Type ◽  
Content Type ◽  
Host Range Expansion ◽  
Novel Host

ABSTRACTRNA viruses are capable of rapid host shifting, typically due to a point mutation that confers expanded host range. As additional point mutations are necessary for further expansions, epistasis among host range mutations can potentially affect the mutational neighborhood and frequency of niche expansion. We mapped the mutational neighborhood of host range expansion using three genotypes of the double-stranded RNA (dsRNA) bacteriophage φ6 (wild type and two isogenic host range mutants) on the novel hostPseudomonas syringaepv. atrofaciens. Both Sanger sequencing of 50P. syringaepv. atrofaciens mutant clones for each genotype and population Illumina sequencing revealed the same high-frequency mutations allowing infection ofP. syringaepv. atrofaciens. Wild-type φ6 had at least nine different ways of mutating to enter the novel host, eight of which are in p3 (host attachment protein gene), and 13/50 clones had unchanged p3 genes. However, the two isogenic mutants had dramatically restricted neighborhoods: only one or two mutations, all in p3. Deep sequencing revealed that wild-type clones without mutations in p3 likely had changes in p12 (morphogenic protein), a region that was not polymorphic for the two isogenic host range mutants. Sanger sequencing confirmed that 10/13 of the wild-type φ6 clones had nonsynonymous mutations in p12, and 2 others had point mutations in p9 and p5. None of these genes had previously been associated with host range expansion in φ6. We demonstrate, for the first time, epistatic constraint in an RNA virus due to host range mutations themselves, which has implications for models of serial host range expansion.IMPORTANCERNA viruses mutate rapidly and frequently expand their host ranges to infect novel hosts, leading to serial host shifts. Using an RNA bacteriophage model system (Pseudomonasphage φ6), we studied the impact of preexisting host range mutations on another host range expansion. Results from both clonal Sanger and Illumina sequencing show that extant host range mutations dramatically narrow the neighborhood of potential host range mutations compared to that of wild-type φ6. This research suggests that serial host-shifting viruses may follow a small number of molecular paths to enter additional novel hosts. We also identified new genes involved in φ6 host range expansion, expanding our knowledge of this important model system in experimental evolution.

scholarly journals Natural Bred ε2-Phages Have an Improved Host Range and Virulence against Uropathogenic Escherichia coli over Their Ancestor Phages

Antibiotics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1337
Author(s):  
Maria Loose ◽  
David Sáez Moreno ◽  
Michele Mutti ◽  
Eva Hitzenhammer ◽  
Zehra Visram ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Host Range ◽  
Phage Therapy ◽  
Uropathogenic Escherichia Coli ◽  
Sequence Type ◽  
Wild Type ◽  
E Coli ◽  
Genetic Sequences ◽  
Tract Infections

Alternative treatments for Escherichia coli infections are urgently needed, and phage therapy is a promising option where antibiotics fail, especially for urinary tract infections (UTI). We used wastewater-isolated phages to test their lytic activity against a panel of 47 E. coli strains reflecting the diversity of strains found in UTI, including sequence type 131, 73 and 69. The plaquing host range (PHR) was between 13 and 63%. In contrast, the kinetic host range (KHR), describing the percentage of strains for which growth in suspension was suppressed for 24 h, was between 0% and 19%, substantially lower than the PHR. To improve the phage host range and their efficacy, we bred the phages by mixing and propagating cocktails on a subset of E. coli strains. The bred phages, which we termed evolution-squared ε2-phages, of a mixture of Myoviridae have KHRs up to 23% broader compared to their ancestors. Furthermore, using constant phage concentrations, Myoviridae ε2-phages suppressed the growth of higher bacterial inocula than their ancestors did. Thus, the ε2-phages were more virulent compared to their ancestors. Analysis of the genetic sequences of the ε2-phages with the broadest host range reveals that they are mosaic intercrossings of 2–3 ancestor phages. The recombination sites are distributed over the whole length of the genome. All ε2-phages are devoid of genes conferring lysogeny, antibiotic resistance, or virulence. Overall, this study shows that ε2-phages are remarkably more suitable than the wild-type phages for phage therapy.

scholarly journals A Tail Fiber Protein and a Receptor-Binding Protein Mediate ICP2 Bacteriophage Interactions with Vibrio cholerae OmpU

2021 ◽  
Author(s):  
Andrea N.W. Lim ◽  
Minmin Yen ◽  
Kimberley D. Seed ◽  
David W. Lazinski ◽  
Andrew Camilli
Keyword(s):  
Host Range ◽  
Vibrio Cholerae ◽  
Receptor Binding ◽  
Binding Protein ◽  
Mutant Phenotype ◽  
Tail Fiber ◽  
Missense Mutations ◽  
Wild Type ◽  
Stool Samples ◽  
Receptor Binding Protein

AbstractICP2 is a virulent bacteriophage (phage) that preys on Vibrio cholerae. ICP2 was first isolated from cholera patient stool samples. Some of these stools also contained ICP2-resistant isogenic V. cholerae strains harboring missense mutations in the trimeric outer membrane porin protein OmpU, identifying it as the ICP2 receptor. In this study, we identify the ICP2 proteins that mediate interactions with OmpU by selecting for ICP2 host-range mutants within infant rabbits infected with a mixture of wild type and OmpU mutant strains. ICP2 host-range mutants had missense mutations in putative tail fiber gene gp25 and putative adhesin gp23. Using site-specific mutagenesis we show that single or double mutations in gp25 are sufficient to generate the host-range mutant phenotype. However, at least one additional mutation in gp23 is required for robust plaque formation on specific OmpU mutants. Mutations in gp23 alone were insufficient to give a host-range mutant phenotype. All ICP2 host-range mutants retained the ability to plaque on wild type V. cholerae cells. The strength of binding of host-range mutants to V. cholerae correlated with plaque morphology, indicating that the selected mutations in gp25 and gp23 restore molecular interactions with the receptor. We propose that ICP2 host-range mutants evolve by a two-step process where, first, gp25 mutations are selected for their broad host-range, albeit accompanied by low level phage adsorption. Subsequent selection occurs for gp23 mutations that further increase productive binding to specific OmpU alleles, allowing for near wild type efficiencies of adsorption and subsequent phage multiplication.ImportanceConcern over multidrug-resistant bacterial pathogens, including Vibrio cholerae, has led to a renewed interest in phage biology and their potential for phage therapy. ICP2 is a genetically unique virulent phage isolated from cholera patient stool samples. It is also one of three phages in a prophylactic cocktail shown to be effective in animal models of infection and the only one of the three that requires a protein receptor (OmpU). This study identifies a ICP2 tail fiber and a receptor binding protein and examines how ICP2 responds to the selective pressures of phage-resistant OmpU mutants. We found that this particular co-evolutionary arms race presents fitness costs to both ICP2 and V. cholerae.

scholarly journals SELECTION FOR A LARGE GENETIC DUPLICATION IN SALMONELLA TYPHIMURIUM

Genetics ◽  
1975 ◽  
Vol 80 (2) ◽  
pp. 227-237
Author(s):  
Daniel S Straus ◽  
George R Hoffmann
Keyword(s):  
Salmonella Typhimurium ◽  
Simple Procedure ◽  
Selective Medium ◽  
Reca Gene ◽  
Wild Type ◽  
E Coli ◽  
Selection For ◽  
Spontaneous Frequency ◽  
Very High ◽  
Tandem Duplications

ABSTRACT Salmonella typhimurium strains containing a duplication of nearly a third of the genome have been isolated by a simple procedure involving selection for improved utilization of L-malate as sole carbon source. The duplication occurs at a very high spontaneous frequency. Strains containing the duplication can be isolated selectively on malate medium, or by a non-selective procedure involving Hfr conjugation. When strains containing the duplication are maintained on non-selective medium, the duplication is readily lost. Genetic evidence suggests that the duplication is chromosomal and tandem. The fact that the recA gene is included in the duplication has been used to obtain evidence that the recA1 marker is recessive to its wild-type allele. Unlike tandem duplications previously described in E. coli, the duplication described in this report appears to have unique endpoints

scholarly journals Isolation and sequencing of three RB49-like bacteriophages infecting O antigen-producing E. coli strains

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 1113
Author(s):  
Alexander Efimov ◽  
Eugene Kulikov ◽  
Alla Golomidova ◽  
Ilya Belalov ◽  
Vladislav Babenko ◽  
...  
Keyword(s):  
Cell Surface ◽  
Host Range ◽  
Tail Fiber ◽  
Long Tail ◽  
E Coli ◽  
Receptor Recognition ◽  
Recognition Protein ◽  
Host Range Determination ◽  
Range Determination ◽  
O Antigens

E. coli strains 4s, F5 and F17, whose O antigens are structurally characterized and shown to effectively shield the cell surface from bacteriophage attack, were used as the hosts to isolate novel RB49-like bacteriophages. Three  novel phage isolates were obtained, and their genomes were sequenced and annotated. Despite high overall identity levels of these genomic sequences, the variants of large distal tail fiber subunit, orthologous to the bacteriophage T2 long tail receptor recognition protein gp38, were unique for each phage, suggesting their role in host range determination. The annotated genomes are available via NCBI Genbank, acc. numbers MZ504876-MZ504878.

scholarly journals The Inheritance of the Glucose Component of the Phage Nucleic Acids

1961 ◽  
Vol 44 (3) ◽  
pp. 585-603 ◽  
Author(s):  
Margeris A. Jesaitis
Keyword(s):  
Nucleic Acid ◽  
Host Range ◽  
Chemical Properties ◽  
Serial Passage ◽  
The Other ◽  
Wild Type ◽  
Or Efficiency ◽  
Glucose Content ◽  
E Coli ◽  
Type Strains

The wild type strains of T2 and T6 bacteriophages differ in their host range specificity, efficiency of plating on E. coli K12, and in glucose content. A study of the inheritance of these three differentiating characteristics has revealed that they are transmitted both upon serial passage of the viruses and when the two phages are crossed. It has been found, furthermore, that an extensive recombination takes place upon crossing. Four types of hybrid phages have been isolated from the progeny of crosses, which had a glucose content of one of the parental phages, and either the host range specificity or efficiency of plating or both of the other. The characteristics of each hybrid were found to be hereditarily stable. It has been concluded that the transmission of the characteristics under consideration is determined genetically and that the genes which control them are not closely linked. Since the glucose content of a phage is determined by the degree of glucosylation of its nucleic acid, the T2 and T6 phages apparently contain genes which control certain chemical properties of their nucleic acid.

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