scholarly journals Analysing Parallel Strategies to Alter the Host Specificity of Bacteriophage T7

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 556
Author(s):  
Ákos Avramucz ◽  
Christian Møller-Olsen ◽  
Aurelija M. Grigonyte ◽  
Yanahan Paramalingam ◽  
Andrew Millard ◽  
...  
Keyword(s):  
Host Specificity ◽  
Selection Method ◽  
Wild Type ◽  
Specific Receptor ◽  
Phenotypic Properties ◽  
New Host ◽  
Pcr Screening ◽  
Ligand Type ◽  
Phage Propagation ◽  
K1 Capsule

The recognition and binding of host bacteria by bacteriophages is most often enabled by a highly specific receptor–ligand type of interaction, with the receptor-binding proteins (RBPs) of phages being the primary determinants of host specificity. Specifically modifying the RBPs could alter or extend the host range of phages otherwise exhibiting desired phenotypic properties. This study employed two different strategies to reprogram T7 phages ordinarily infecting commensal K12 Escherichia coli strains to infect pathogen-associated K1-capsule-expressing strains. The strategies were based on either plasmid-based homologous recombination or bacteriophage recombineering using electroporated DNA (BRED). Our work pursued the construction of two genetic designs: one replacing the gp17 gene of T7, the other replacing gp11, gp12, and gp17 of T7 with their K1F counterparts. Both strategies displayed successful integration of the K1F sequences into the T7 genome, detected by PCR screening. Multiple methods were utilised to select or enrich for chimeric phages incorporating the K1F gp17 alone, including trxA, host-specificity, and CRISPR-Cas-based selection. Irrespective of the selection method, the above strategy yielded poorly reproducible phage propagation on the new host, indicating that the chimeric phage was less fit than the wild type and could not promote continual autonomous reproduction. Chimeric phages obtained from BRED incorporating gp11-12 and gp17, however, all displayed infection in a 2-stage pattern, indicating the presence of both K1F and T7 phenotypes. This study shows that BRED can be used as a tool to quickly access the potential of new RBP constructs without the need to engineer sustainably replicating phages. Additionally, we show that solely repurposing the primary RBP is, in some cases, insufficient to produce a viable chimeric phage.

scholarly journals A Point Mutation in the mma3 Gene Is Responsible for Impaired Methoxymycolic Acid Production in Mycobacterium bovis BCG Strains Obtained after 1927

2000 ◽  
Vol 182 (12) ◽  
pp. 3394-3399 ◽  
Author(s):  
Marcel A. Behr ◽  
Benjamin G. Schroeder ◽  
Jacquelyn N. Brinkman ◽  
Richard A. Slayden ◽  
Clifton E. Barry
Keyword(s):  
Point Mutation ◽  
Mycobacterium Bovis ◽  
Mycobacterium Smegmatis ◽  
Pasteur Institute ◽  
Wild Type ◽  
Phenotypic Properties ◽  
Site Specific ◽  
Mutant Population ◽  
Mycolic Acids

ABSTRACT BCG vaccines are substrains of Mycobacterium bovisderived by attenuation in vitro. After the original attenuation (1908 to 1921), BCG strains were maintained by serial propagation in different BCG laboratories (1921 to 1961). As a result, various BCG substrains developed which are now known to differ in a number of genetic and phenotypic properties. However, to date, none of these differences has permitted a direct phenotype-genotype link. Since BCG strains differ in their abilities to synthesize methoxymycolic acids and since recent work has shown that the mma3 gene is responsible for O-methylation of hydroxymycolate precursors to form methoxymycolic acids, we analyzed methoxymycolate production andmma3 gene sequences for a genetically defined collection of BCG strains. We found that BCG strains obtained from the Pasteur Institute in 1927 and earlier produced methoxymycolates in vitro but that those obtained from the Pasteur Institute in 1931 and later all failed to synthesize methoxymycolates, and furthermore, themma3 sequence of the latter strains differs from that ofMycobacterium tuberculosis H37Rv by a point mutation at bp 293. Site-specific introduction of this guanine-to-adenine mutation into wild-type mma3 (resulting in the replacement of glycine 98 with aspartic acid) eliminated the ability of this enzyme to produce O-methylated mycolic acids when the mutant was cloned in tandem with mma4 into Mycobacterium smegmatis. These findings indicate that a point mutation in mma3 occurred between 1927 and 1931, and that this mutant population became the dominant clone of BCG at the Pasteur Institute.

Cyanoacrylate Inhibitors of Photosynthetic Electron Transport in Atrazine Susceptible and Atrazine Resistant Brassica Chloroplasts

1987 ◽  
Vol 42 (6) ◽  
pp. 670-673 ◽  
Author(s):  
John N. Phillips ◽  
John L. Huppatz
Keyword(s):  
Electron Transport ◽  
Inhibitory Activity ◽  
Photosynthetic Electron Transport ◽  
Resistant Mutant ◽  
Herbicidal Activity ◽  
Optical Isomers ◽  
Wild Type ◽  
Specific Receptor ◽  
Receptor Sites ◽  
Alkyl Moiety

Comparison of the p/50 values for a series of cyanoacrylate derivatives in chloroplasts isolated from atrazinc susccptiblc (wild type) and atrazine resistant (mutant) Brassica napus biotvpes reveal that the degree and direction of discrimination can vary from being 200- fold more active against the wild type to 10-fold more active against the mutant. There appears to be a direct correlation between the level of inhibitory activity in thylakoids isolated from “susceptible” chloroplasts and the level of discrimination between “susceptible” and “resistant” chloroplasts - a correlation which can be improved by allowing for variations in molecular hydrophobicity. Studies with optically active ethoxyethyl-3-alkyl-2-cyano-3-α-methylbenzylamino acrylates suggest that there are specific receptor sites present in both “susceptible” and “resistant” chloroplasts for both the a-methylbenzyl chiral centre and the 3-alkyl moiety. There is a direct relationship between photosynthetic electron transport inhibitory activity and herbicidal activity of optical isomers.

scholarly journals Host Specificity of the Parasitic Wasp Anaphes flavipes (Hymenoptera: Mymaridae) and a New Defence in Its Hosts (Coleoptera: Chrysomelidae: Oulema spp.)

Insects ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 175
Author(s):  
Alena Samková ◽  
Jiří Hadrava ◽  
Jiří Skuhrovec ◽  
Petr Janšta
Keyword(s):  
Biological Control ◽  
Czech Republic ◽  
Host Specificity ◽  
Parasitic Wasp ◽  
Leaf Beetle ◽  
Host Defence ◽  
Pest Species ◽  
New Host ◽  
Leaf Beetles ◽  
Study Laboratory

The parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae) is an important egg parasitoid of cereal leaf beetles. Some species of cereal leaf beetle co-occur in the same localities, but the host specificity of the wasp to these crop pests has not yet been examined in detail. A lack of knowledge of host specificity can have a negative effect on the use of this wasps in biological control programs addressed to specific pest species or genus. In this study, laboratory experiments were conducted to assess the host specificity of A. flavipes for three species of cereal leaf beetles (Oulema duftschmidi Redtenbacher, 1874, Oulema gallaeciana Heyden, 1879 and Oulema melanopus Linnaeus, 1758) in central Europe. For the first time, a new host defence against egg parasitoids occurring in O. gallaeciana from localities in the Czech Republic, a strong dark sticky layer on the egg surface, was found and described. The host specificity of A. flavipes was studied in the locality with the presence of this defence on O. gallaeciana eggs (the dark sticky layer) (Czech Republic) and in a control locality (Germany), where no such host defence was observed. Contrary to the idea that a host defence mechanism can change the host specificity of parasitoids, the wasps from these two localities did not display any differences in that. Respectively, even though it has been observed that eggs with sticky dark layer can prevent parasitization, the overall rate of parasitization of the three species of cereal beetles has not been affected. However, in our view, new host defence can influence the effects of biological control, as eggs of all Oulema spp. in the locality are protected against parasitization from the wasps stuck on the sticky layer of the host eggs of O. gallaeciana.

scholarly journals New host record of some gastrointestinal parasites of Irrawaddy squirrel (Callosciurus pygerythrus) from Chittagong, Bangladesh

2018 ◽  
Vol 46 (2) ◽  
pp. 87-103
Author(s):  
Md Afzal Hussain ◽  
Rajib Acharjee ◽  
Benazir Ahmed
Keyword(s):  
Host Specificity ◽  
Parasite Species ◽  
Host Record ◽  
Gastrointestinal Parasites ◽  
Hymenolepis Diminuta ◽  
University Campus ◽  
Gi Tract ◽  
New Host ◽  
New Host Record ◽  
Syphacia Obvelata

Gastrointestinal (GI) tract of 60 Irrawaddy squirrels (Callosciurus pygerythrus) were collected between September 2013 and August 2014 from four different spots of Chittagong University campus and its adjacent areas to study the ento-helminth fauna. Eight different parasite species were identified - one belonging to Cestoda and represented by Hymenolepis diminuta, and the remaining seven were to Nematoda viz., Strongyloides callosciurus, Trichuris ovis, Monodontus sp., Cyclodontostomum purvisi, Moguranema nipponicum, Ascarops talpa and Syphacia obvelata. The nematodes were found as dominant species most preferably inhabiting the small intestine. The present host is the new host record for all of these parasites and S. callosciurus, T. ovis, Monodontus sp., M. nipponicum and A. talpa are the new records for Bangladesh too. All these parasites have very wide host specificity, though most of them are restricted to various rodent hosts but H. diminuta and S. callosciurus were found to have more wider specificity, including other vertebrates too. All identified parasites might have been acquired from the environment where the host inhabits, since host specificity perspective no parasites were found to be specific to the present host. H. diminuta and Syphacia obvelata might have zoonotic role to other wild animals and human and vice versa. Bangladesh J. Zool. 46(2): 87-103, 2018

On Urceolaria mitra (Protozoa, Peritricha) epizoic on North American flatworms

1968 ◽  
Vol 46 (5) ◽  
pp. 981-985 ◽  
Author(s):  
Ian R. Ball ◽  
C. H. Fernando
Keyword(s):  
North America ◽  
Host Specificity ◽  
North American ◽  
Biological Data ◽  
Temporary Waters ◽  
New Host ◽  
First Time

Urceolaria mitra (von Sieb.) is described for the first time from North America, and new host and geographic records are given. Brief biological data on host specificity, distribution and dispersal, and survival of the epizoite in temporary waters are also provided.

scholarly journals Comparative Study of the Roles of AhpC and KatE as Respiratory Antioxidants in Brucella abortus 2308

2010 ◽  
Vol 192 (19) ◽  
pp. 4912-4922 ◽  
Author(s):  
Kendra H. Steele ◽  
John E. Baumgartner ◽  
Michelle Wright Valderas ◽  
R. Martin Roop
Keyword(s):  
Brucella Abortus ◽  
Double Mutant ◽  
Aerobic Metabolism ◽  
The Other ◽  
Wild Type ◽  
Phenotypic Properties ◽  
Experimental Findings ◽  
Oxide Synthase ◽  
Derivatives Of ◽  
Inducible Nitric Oxide

ABSTRACT Brucella strains are exposed to potentially toxic levels of H2O2 both as a consequence of their aerobic metabolism and through the respiratory burst of host phagocytes. To evaluate the relative contributions of the sole catalase KatE and the peroxiredoxin AhpC produced by these strains in defense against H2O2-mediated toxicity, isogenic katE, ahpC, and katE ahpC mutants were constructed and the phenotypic properties of these mutants compared with those of the virulent parental strain B. abortus 2308. The results of these studies indicate that AhpC is the primary detoxifier of endogenous H2O2 generated by aerobic metabolism. KatE, on the other hand, plays a major role in scavenging exogenous and supraphysiologic levels of H2O2, although this enzyme can play a supporting role in the detoxification of H2O2 of endogenous origin if AhpC is absent. B. abortus ahpC and katE mutants exhibit wild-type virulence in C57BL/6 and BALB/c mice, but the B. abortus ahpC katE double mutant is extremely attenuated, and this attenuation is not relieved in derivatives of C57BL/6 mice that lack NADPH oxidase (cybb) or inducible nitric oxide synthase (Nos2) activity. These experimental findings indicate that the generation of endogenous H2O2 represents a relevant environmental stress that B. abortus 2308 must deal with during its residence in the host and that AhpC and KatE perform compensatory roles in detoxifying this metabolic H2O2.

scholarly journals Phenotypic properties of R factors ofPseudomonas aeruginosa:R factors transferable only inPseudomonas aeruginosa

1974 ◽  
Vol 23 (3) ◽  
pp. 251-257 ◽  
Author(s):  
P. M. Chandler ◽  
V. Krishnapillai
Keyword(s):  
Drug Resistance ◽  
Shigella Flexneri ◽  
Low Frequency ◽  
Wild Type ◽  
Phenotypic Properties ◽  
Specific Phage ◽  
Group 2 ◽  
R Factors ◽  
Type Strains ◽  
Group 1

SUMMARYA study was made of the R factors from two multiply drug resistant wild type isolates ofPseudomonas aeruginosafrom a Birmingham hospital (Lowburyet al.1969) from which, in contrast to other strains from the same source (Chandler & Krishnapillai, 1974a), drug resistance was not transferable toEscherichia coliK12 orSalmonella typhimurium. Transfer of drug resistance occurred at a low frequency toShigella flexneri, although drug resistance in this species was subsequently non-transferable.InP. aeruginosathere are several features of these two R factors which distinguish them from the group 1 and 2 R factors described previously (Chandler & Krishnapillai, 1974a). Although coding for resistance to neomycin and tetracycline, they did not express this resistance in two strains ofP. aeruginosaexamined, in contrast to the wild type strains they were isolated in.The control of transfer of the two R factors is different to the group 1 and 2 R factors in that derepression of transfer could be demonstrated following physiological treatments or mutagenesis. The R factors of this third group were compatible with the group 2 R factors, but did not repress their pilus synthesis on the basis of R factor specific phage plating.

scholarly journals Ant-fungus Interactions: Laboulbenia camponoti Batra in Italy and a New Host for L. formicarum Thaxter (Fungi: Ascomycota, Laboulbeniales)

Sociobiology ◽  
2016 ◽  
Vol 63 (3) ◽  
pp. 950 ◽  
Author(s):  
Kiko Gómez ◽  
Xavier Espadaler ◽  
Sergi Santamaria
Keyword(s):  
Host Specificity ◽  
Present Knowledge ◽  
Lasius Niger ◽  
New Host ◽  
Ant Fungus ◽  
World Distribution

One Laboulbenia species is added to the checklist of Italian fungi. Laboulbenia camponoti was detected on the ant Camponotus aethiops. Additionally, L. formicarum was found on a new host (Lasius niger) in France. An updated map of world distribution for the two Laboulbenia is presented. Based on present knowledge, L. camponoti shows a much higher structural and phylogenetic host specificity than L. formicarum.

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