Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “host range”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources
PubMed1991

Conjugational transfer of recombinant DNA in cultures and in soils: host range of Pseudomonas putida TOL plasmids.

Recombinant TOL plasmid pWWO-EB62 allows Pseudomonas putida to grow on p-ethylbenzoate. This plasmid can be transferred to other microorganisms, and its catabolic functions for the metabolism of alkylbenzoates are expressed in a limited number of gram-negative bacteria, including members of pseudomonad rRNA group I and Escherichia coli. Transfer of the recombinant plasmid to Erwinia chrysanthemi was observed, but transconjugants failed to grow on alkylbenzoates because they lost catabolic functions. Pseudomonads belonging to rRNA groups II, III, and IV, Acinetobacter calcoaceticus, and Alcaligenes sp. could not act as recipients for TOL, either because the plasmid was not transferred or because it was not stably maintained. The frequency of transfer of pWWO-EB62 from P. putida as a donor to pseudomonads belonging to rRNA group I was on the order of 1 to 10(-2) transconjugant per recipient, while the frequency of intergeneric transfer ranged from 10(-3) to 10(-7) transconjugant per recipient. The profile of potential hosts was conserved when the donor bacterium was Escherichia coli or Erwinia chrysanthemi instead of P. putida. No intergeneric gene transfer of the recombinant TOL plasmid was observed in soils; however, intraspecies transfer did take place. Intraspecies transfer of TOL in soils was affected by the type of soil used, the initial inoculum size, and the presence of chemicals that could affect the survival of the donor or recipient bacteria.

Anti-Bacterial Agents↗
PubMed1992

Comparative Study of 35 Bacteriophages of Lactobacillus helveticus: Morphology and Host Range.

This survey included 23 phages isolated from cheese whey and 12 temperate phages induced with mitomycin from their lysogenic host strains. All of the phages had an isometric head and a tail with a contractile sheath. In addition, short-tailed (160-nm-long) and long-tailed (260-nm-long) phages were distinguished. Short-tailed phages were by far the most widespread in French cheese factories (32 of the 35 phages studied). The study of phage relationships enabled two large groups of strains to be distinguished: those not or slightly sensitive to phages and those very sensitive to phages. There was an obvious relationship in the first group between phage sensitivity (or resistance) and the geographic origin of the strains. The second group contained primarily strains from large international collections and those isolated from commercial starters. The relationships among short-tailed phages, either temperate or isolated as lytic, suggest that lysogenic strains could be the major source of phages in French cheese factories.

Journal Article↗
PubMed1995

In Rhizobium meliloti, the operon associated with the nod box n5 comprises nodL, noeA and noeB, three host-range genes specifically required for the nodulation of particular Medicago species.

In Rhizobium meliloti, the genes required for nodulation of legume hosts are under the control of DNA regulatory sequences called nod boxes. In this paper, we have characterized three host-specific nodulation genes, which form a flavonoid-inducible operon down-stream of the nod box n5. The first gene of this operon is identical to the nodL gene identified by Baev and Kondorosi (1992) in R. meliloti strain AK631. The product of the second gene, NoeA, presents some homology with a methyltransferase. nodL mutants synthesize Nod factors lacking the O-acetate substituent. In contrast, in strains carrying a mutation in either noeA or noeB, no modification in Nod-factor structure or production could be detected. On particular hosts, such as Medicago littoralis, mutants of the n5 operon showed a very weak nodule-forming ability, associated with a drastic decrease in the number of infection threads, while nodulation of Medicago truncatula or Melilotus alba was not affected. Thus, nodL noeA and noeB are host-specific nodulation genes. By using a gain-of-function approach, we showed that the presence of nodL, and hence of O-acetylated Nod factors, is a major prerequisite for confering the ability to nodulate alfalfa upon the heterologous bacterium Rhizobium tropici.

Acetylation↗
PubMed2003

pIIICTX, a predicted CTXphi minor coat protein, can expand the host range of coliphage fd to include Vibrio cholerae.

CTXphi is a filamentous bacteriophage that encodes cholera toxin. CTXphi infection of its host bacterium, Vibrio cholerae, requires the toxin-coregulated pilus (TCP) and the products of the V. cholerae tolQRA genes. Here, we have explored the role of OrfU, a predicted CTXphi minor coat protein, in CTXphi infection. Prior to the discovery that it was part of a prophage, orfU was initially described as an open reading frame of unknown function that lacked similarity to known protein sequences. Based on its size and position in the CTXphi genome, we hypothesized that OrfU may function in a manner similar to that of the coliphage fd protein pIII and mediate CTXphi infection as well as playing a role in CTXphi assembly and release. Deletion of orfU from CTXphi dramatically reduced the number of CTXphi virions detected in supernatants from CTXphi-bearing cells. This defect was complemented by expression of orfU in trans, thereby confirming a role for this gene in CTXphi assembly and/or release. To evaluate the requirement for OrfU in CTXphi infection, we introduced fragments of orfU into gIII in an fd derivative to create OrfU-pIII fusions. While fd is ordinarily unable to infect V. cholerae, an fd phage displaying the N-terminal 274 amino acids of OrfU could infect V. cholerae in a TCP- and TolA-dependent fashion. Since our findings indicate that OrfU functions as the CTXphi pIII, we propose to rename OrfU as pIII(CTX). Our data also provide new evidence for a conserved pathway for filamentous phage infection.

Amino Acid Sequence↗
PubMed2003

Deletions in the transmembrane domain of a sindbis virus glycoprotein alter virus infectivity, stability, and host range.

The alphaviruses are composed of two icosahedral protein shells, one nested within the other. A membrane bilayer derived from the host cell is sandwiched between the protein shells. The protein shells are attached to one another by protein domains which extend one of the proteins of the outer shell through the membrane bilayer to attach to the inner shell. We have examined the interaction of the membrane-spanning domain of one of the membrane glycoproteins with the membrane bilayer and with other virus proteins in an attempt to understand the role this domain plays in virus assembly and function. Through incremental deletions, we have reduced the length of a virus membrane protein transmembrane domain from its normal 26 amino acids to 8 amino acids. We examined the effect of these deletions on the assembly and function of virus particles. We found that progressive truncations in the transmembrane domain profoundly affected production of infectious virus in a cyclic fashion. We also found that membrane composition effects protein-protein and protein-membrane interactions during virus assembly.

Amino Acid Sequence↗
PubMed1995

Host-range control of a retroviral disease: Friend erythroleukemia.

Since its discovery in 1957, Friend viral erythroleukemia has been the major model for understanding host genetic barriers to retroviral diseases and has facilitated the discovery of many polymorphic leukemia-control genes of mice. Some of these genes limit helper-virus replication, target-cell (erythroblast) pools or immune responses. At least one host gene appears to block the viral oncoprotein.

Amino Acid Sequence↗
PubMed1999

Recombinants of cucumber mosaic virus (CMV): determinants of host range and symptomatology.

117F and R are subgroup I and II cucumber mosaic virus (CMV) strains, respectively. Whereas I17F induces severe symptoms on all hosts so far tested, R induces generally mild symptoms, except on Nicotiana glutinosa, on which it causes leaf blistering and severe stunting. Pseudorecombinants and recombinants, based on RNAs 1 and 2 from R-CMV, were created by adding either I17F RNA 3 or one of two chimeric RNAs created by exchanging approximate halves of RNA 3 of the two strains. The viruses created were tested on different hosts of the virus. On maize, local necrotic lesions were induced by all strains with the 5' part of RNA 3 from R-CMV, whereas only I17F-CMV induced a systemic infection. The seven solanaceous hosts tested could be classified into two main groups. In the first, RNA 3 was not directly involved in the symptoms that were systemically induced, and the extreme disease severity induced by I17F was correlated with high virus accumulation. In the same hosts, the lesser virulence of R-CMV could reflect a deficiency in long-distance movement, involving RNA 3. The second group included Nicotiana glutinosa where the symptoms induced by R-CMV were determined by the 3' part of RNA 3.

Blotting, Northern↗
PubMed1991

Single amino acid substitutions in the hemagglutinin can alter the host range and receptor binding properties of H1 strains of influenza A virus.

We have previously characterized an influenza A (H1N1) virus which has host-dependent growth and receptor binding properties and have shown that a mutation which removes an oligosaccharide from the tip of the hemagglutinin (HA) by changing Asn-129 to Asp permits this virus to grow to high titer in MDBK cells, (C. M. Deom, A. J. Caton, and I. T. Schulze, Proc. Natl. Acad. Sci. USA 83:3771-3775, 1986). We have now isolated monoclonal antibodies specific for the mutant HA and have used escape mutants to identify alterations in HA sequence which reduce virus yields from MDBK cells without reducing those from chicken embryo fibroblasts. Two types of escape mutants which grow equally well in chicken embryo fibroblasts were obtained. Those with the parent phenotype contain Asn at residue 129 and are glycosylated at that site. Those with the mutant phenotype are unchanged at residue 129 but have a Gly to Glu substitution at residue 158, which is close to residue 129 on the HA1 subunit. Binding assays with neoglycoproteins containing N-acetylneuraminic acid in either alpha 2,3 or alpha 2,6 linkage to galactose showed that the MDBK-synthesized oligosaccharides at Asn-129 reduce binding to both of these receptors, leaving the HA's preference for alpha 2,6 linkages unchanged. Glu at residue 158 greatly reduces binding to both receptors without reducing virus yields from MDBK cells. We conclude that changes in the receptor binding properties of the HA can result either from direct alteration of the HA protein by host cell glycosylation or from mutations in the HA gene and that these changes generate heterogeneity that can contribute to the survival of influenza A virus populations in nature.

Amino Acids↗
PubMedDate not supplied

Mutational analysis of cauliflower mosaic virus gene VI: changes in host range, symptoms, and discovery of transactivation-positive, noninfectious mutants.

Gene VI of cauliflower mosaic virus (CaMV) has been shown to be a determinant of host specificity of the virus as well as a factor influencing symptom development in infected plants. In addition, it plays a crucial role in viral gene expression through a process of posttranscriptional transactivation. In the present study, linker-insertion mutations within gene VI of a cloned, recombinant cauliflower mosaic virus genome were constructed and tested for infectivity, symptom development on solanaceous plants, and the ability of transactivate viral gene expression. Certain mutations in the first third of the gene resulted in changes in symptoms shown by test plants. Another mutation, also in the first third of the gene, blocked infectivity in the Nicotiana species tested and systemic movement in Datura stramonium. The mutants were also tested in protoplasts for the ability to transactivate virus gene expression. Infectious mutants were invariably positive for transactivation and mutants negative for transactivation were noninfectious. Interestingly, two mutants positive for transactivation were noninfectious, suggesting a second function for gene VI in the infection process. These results further suggest a role for gene VI, as yet not fully understood, in systemic movement of the virus in infected plants.

Amino Acid Sequence↗