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PubMed2006

Characterization of Streptococcus thermophilus host range phage mutants.

To investigate phage-host interactions in Streptococcus thermophilus, a phage-resistant derivative (SMQ-301R) was obtained by challenging a Tn917 library of phage-sensitive strain S. thermophilus SMQ-301 with virulent phage DT1. Mutants of phages DT1 and MD2 capable of infecting SMQ-301 and SMQ-301R were isolated at a frequency of 10(-6). Four host range phage mutants were analyzed further and compared to the two wild-type phages. Altogether, three genes (orf15, orf17, and orf18) contained point mutations leading to amino acid substitutions and were responsible for the expanded host range. These three proteins were also identified in both phages by N-terminal sequencing and/or matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. The results suggest that at least three phage structural proteins may be involved in phage-host interactions in S. thermophilus.

Amino Acid Sequence↗
PubMed1989

Nucleotide sequence, evolutionary origin and biological role of a rearranged cytokinin gene isolated from a wide host range biotype III Agrobacterium strain.

A DNA fragment with homology to the cytokinin (ipt) gene from biotype I Agrobacterium tumefaciens strain Ach5 was cloned from the Ti plasmid of the wide host range biotype III Agrobacterium strain Tm-4 and sequenced. The fragment contains an intact ipt coding sequence. However, the 3' non-coding region of this ipt gene is rearranged due to a 0.9 kb deletion fusing it to the 3' coding region of the neighbouring gene 6a, most of which was found to be deleted. The Tm-4 ipt gene is strongly related to the partially deleted ipt gene of the limited host range biotype III strain Ag162. To test its biological activity, the Tm-4 ipt gene was inserted into a specially constructed, disarmed Ti vector lacking tzs and tested on tobacco, where the rearranged ipt gene induced shoot formation. The cloned Tm-4 ipt gene was mutated with Tn5 and the intact gene on the wild-type Tm-4 Ti plasmid was replaced by the mutated gene. The resulting strain was avirulent on tobacco but normally virulent on the natural host of the wild-type strain Tm-4, grapevine. As the biotype I 6b gene diminishes the effect of a corresponding ipt gene, a larger Tm-4 fragment carrying both the ipt gene and an adjacent 6b-like gene was also tested on tobacco and compared with the Tm-4 ipt fragment alone and with an ipt and 6b/ipt fragment derived from Ach5. The Tm-4 6b gene diminishes the effect of the Tm-4 ipt gene, showing the Tm-4 6b gene to be active as well. The Tm-4 6b/ipt combination is less effective than the Ach5 combination. These results provide further insight into the molecular basis of the host range differences between limited host range and wide host range biotype III Agrobacterium strains and show that the WHR cytokinin gene, although active, does not significantly contribute to tumour formation on the natural host of the WHR biotype III strains, grapevine.

Base Sequence↗
PubMed2000

Complementation of the host range restriction of southern cowpea mosaic virus in bean by southern bean mosaic virus.

Vigna unguiculata (cowpea) and Phaseolus vulgaris (common bean) are permissive hosts for southern cowpea mosaic virus (SCPMV) and southern bean mosaic virus (SBMV), respectively. Neither of these two sobemoviruses systemically infects the permissive host of the other. Although bean cells are permissive for SCPMV RNA synthesis, they do not support the assembly of this virus. Thus, the host range restriction of SCPMV in bean may occur at the level of movement and may involve the inability of SCPMV to assemble in this host. In this study, it was demonstrated that SCPMV accumulates in an encapsidated form in the inoculated and systemic leaves of bean plants following coinoculation with SBMV. No evidence was observed that the SCPMV that accumulated in coinoculated bean plants had an altered host range relative to wild-type SCPMV. These results suggested that SBMV complemented the host range restriction of SCPMV in bean. Additional experiments demonstrated that cowpea protoplasts are permissive for SBMV RNA synthesis and assembly. It was concluded from these results that the host range restriction of SBMV in cowpea occurs at the level of movement. In mixed infections of cowpea with SCPMV and SBMV, the latter was recovered from the inoculated but not the systemic leaves. Its recovery from the inoculated leaves, however, was not dependent on the presence of SCPMV in the inoculum. From these results, it was concluded that SCPMV did not complement the host range restriction of SBMV in cowpea.

Comovirus↗
PubMed1988

Host Ranges of the IncN Group Plasmid pCU1 and Its Minireplicon in Gram-Negative Purple Bacteria.

The bacterial host ranges of the conjugatively self-transmissible IncN group plasmid pCU1 and its mobilizable miniderivative, pCU785, were examined. Species of the gram-negative purple bacteria were chosen for this study. Conjugative mobilization of pCU785 into a wide variety of bacteria was facilitated by the presence of oriT of the broad-host-range plasmid RK2 in pCU785. Although the host range of the IncN tra system of pCU1 is broad, the host range of its replicon is limited. However, the pCU1 replicon can be maintained in Agrobacterium, Bradyrhizobium, and Rhizobium species under conditions that select for plasmid maintenance. It is lost efficiently from these populations on release of selection.

Journal Article↗
PubMed1990

Host-range modifications of bacteriophage epsilon 15.

Host-range modifications were observed after multiplication of bacteriophage epsilon 15 on Salmonella strains belonging to five serovars. The phage preparations obtained were tested at RTD (routine test dilution) on strains belonging to the same serovars. In each serovar, three kinds of reaction patterns were observed: (a) specific sensitivity only to the phage multiplied on the same serovar; (b) sensitivity to all host-range modifications of the phage; (c) lack of sensitivity to all phage preparations, at RTD.

Bacteriophages↗
PubMed1983

Isolation and characterization of host range mutants of avian sarcoma virus.

Two host range mutants of avian sarcoma virus (ASV) were isolated from a clone of the Bratislava 77 strain, subgroup C (B77-C). An HR- mutant was obtained by adaptation to duck cells and showed almost the same efficiencies of transformation (e.o.t.) and growth in cultures of chick embryo fibroblasts (CEF) and duck embryo fibroblasts (DEF). An HR+ mutant showed lower e.o.t. and slower growth on DEF than on CEF. Characterization of these mutants and wild-type B77-C showed that (i) unlike the host range mutants reported previously, these mutants and wild-type B77-C have common antigenicity, (ii) the number of infective centres is almost the same for the two mutants and the wild-type, and so the adsorption and integration of these viruses are similar, and (iii) the content of viral RNA in DEF infected with HR- is increased and decreased in the case of HR+ compared with the wild-type.

Animals↗
PubMed1999

Host range relationships and the evolution of canine parvovirus.

Canine parvovirus (CPV) is an example of an unusual class of emerging virus-those that gain an altered host range through genetic variation and subsequently become widespread pathogens of their new and previously resistant host species. CPV was first detected in 1978 as the cause of new diseases in dogs throughout the world, when it rapidly spread throughout domestic populations, as well as becoming widespread in wild dogs. CPV was soon shown to be a variant of the long recognized feline panleukopenia virus (FPV), from which it differed in less than 1% at the nucleotide sequence level. Genetic analysis showed that virtually all of the biological differences between CPV and FPV, including the canine host range, were determined by three or four sequence differences in the viral capsid protein gene. Analysis of the atomic structures of the CPV and FPV capsids showed that the differences controlling host range were located within two different structural regions and were exposed on the capsid surface. The CPV which first emerged in 1978 appeared to be derived from a single ancestral sequence, which has allowed the ready analysis of the subsequent evolution of the virus in nature. Sequence analysis has also revealed that CPV strains have undergone a series of evolutionary selections in nature which have resulted in the global distribution of new virus variants. This was first seen in the global replacement between 1979 and 1981 of the original (1978) strain of the virus by a genetically and antigenically variant strain, and the subsequent widespread selection of other variants which have also become globally distributed. The genetic and antigenic variation in the virus strains was also correlated with changes in the host range of the virus, in particular in the ability to replicate in cats, and in canine host range differences seen in tissue culture cells.

Amino Acid Sequence↗
PubMed2003

Modulation of pPS10 host range by plasmid-encoded RepA initiator protein.

We report here the isolation and analysis of novel repA host range mutants of pPS10, a plasmid originally found in Pseudomonas savastanoi. Upon hydroxylamine treatment, five plasmid mutants were selected for their establishment in Escherichia coli at 37 degrees C, a temperature at which the wild-type form cannot be established. The mutations were located in different functional regions of the plasmid RepA initiation protein, and the mutants differ in their stable maintenance, copy number, and ability to interact with sequences of the basic replicon. Four of them have broadened their host range, and one of them, unable to replicate in Pseudomonas, has therefore changed its host range. Moreover, the mutants also have increased their replication efficiency in strains other than E. coli such as Pseudomonas putida and Alcaligenes faecalis. None of these mutations drastically changed the structure or thermal stability of the wild-type RepA protein, but in all cases an enhanced interaction with host-encoded DnaA protein was detected by gel filtration chromatography. The effects of the mutations on the functionality of RepA protein are discussed in the framework of a three-dimensional model of the protein. We propose possible explanations for the host range effect of the different repA mutants, including the enhancement of limiting interactions of RepA with specific host replication factors such as DnaA.

Bacterial Proteins↗
PubMed1998

Determinants of rotavirus host range restriction--a heterologous bovine NSP1 gene does not affect replication kinetics in the pig.

The genetic basis of rotavirus host range restriction (host species specificity) is unknown but the NSP1 (fifth) gene has been implicated in some studies. We studied the replication kinetics in vivo of a NSP1 gene monoreassortant, E11, to assess the influence of a heterologous NSP1 gene on the ability to replicate in pigs. The monoreassortant possessed 10 genes from the porcine parent rotavirus SW20/21, which replicated productively in pigs, and the NSP1 gene from the bovine rotavirus UK which produced an abortive infection in pigs. Groups of up to four pigs were inoculated orally with 10(5) to 10(6) TCID50 of the monoreassortant, the porcine parent rotavirus, or the bovine parent rotavirus or were sham inoculated. The monoreassortant replicated productively in pigs with replication kinetics almost identical to the porcine parent rotavirus. During a 9-day observation period after inoculation, the number of days with virus in the faeces, the onset and duration of virus excretion, and peak titres in faeces were similar for the monoreassortant and the parent porcine rotavirus. The genetic composition of the viruses excreted in the faeces was confirmed as that of the inocula by PAGE. Thus possession of a heterologous NSP1 gene from a bovine rotavirus which failed to replicate in pigs did not produce an abortive infection or affect the replication kinetics in vivo. The genetic basis of host range restriction between porcine and bovine rotaviruses remains to be established.

Animals↗
PubMed1984

Characterization of the infections of permissive and nonpermissive cells by host range mutants of vesicular stomatitis virus defective in RNA methylation.

Two host range mutants of VSV, hr 1 and hr 8, which, unlike the wild-type virus, have a mRNA methylation defect and direct the in vitro synthesis of full-length capped but unmethylated viral mRNAs have been described previously (S.M. Horikami and S.A. Moyer, 1982, Proc. Natl, Acad. Sci. USA 79, 7694-7698). It is shown that the in vivo nonpermissive infection of HEp-2 cells by either of these two mutants is characterized by the reduced synthesis of full-length mRNAs at levels characteristic of primary transcription and the total lack of synthesis of genome-length RNA. The VSV mRNAs synthesized by either mutant in HEp-2 cells are not translated either in vivo or in vitro in mRNA-dependent rabbit reticulocyte lysates. Subsequent isolation and analysis of the mRNAs from infected HEp-2 cells has shown that the 5' termini of the messages contain a cap structure which is guanylylated, but unmethylated (GpppA), a finding that might account for the lack of translatability. Hence these mutants are unable to properly methylate mRNAs whether they are synthesized in vitro or in vivo within nonpermissively infected cells. It is also shown that unlike hr 1, the undermethylation of mRNA synthesized by hr 8 is partially reversible by the addition of high levels of AdoMet in vitro. It is interesting to note, therefore, that permissive baby hamster kidney (BHK) cells have a 10-fold higher level of endogenous AdoMet than the nonpermissive HEp-2 cells. Unlike singly infected cells, the coinfection of HEp-2 cells with either hr mutant and a poxvirus yields a permissive infection for these two host range mutants. Analysis of the VSV mRNAs produced in vivo under the conditions of rescue reveals the presence of fully methylated caps (7mGppp(m)Am), suggesting that poxvirus may rescue the mutants by converting the VSV mRNAs to a translationally active form due to methylation by the cytoplasmic poxvirus mRNA methyltransferase enzymes. Both mutants are, however, able to grow normally in permissive BHK cells. An analysis of the translationally active mRNAs from infected permissive cells shows the presence primarily of a 5'-monomethylated cap, 7mGpppA. Finally, we have examined the nonpermissive infections of two other host range mutants of VSV (hr 5 and hr 7). Unlike mutants hr 1 and hr 8 described above, these two mutants synthesize mRNA in HEp-2 cells which is translated both in vivo and in vitro.

Animals↗
PubMed1988

Improved broad-host-range plasmids for DNA cloning in gram-negative bacteria.

Improved broad-host-range plasmid vectors were constructed based on existing plasmids RSF1010 and RK404. The new plasmids pDSK509, pDSK519, and pRK415, have several additional cloning sites and improved antibiotic-resistance genes which facilitate subcloning and mobilization into various Gram-negative bacteria. Several new polylinker sites were added to the Escherichia coli plasmids pUC118 and pUC119, resulting in the new plasmids, pUC128 and pUC129. These plasmids facilitate the transfer of cloned DNA fragments to the broad-host-range vectors. Finally, the broad-host-range cosmid cloning vector pLAFR3 was improved by the addition of a double cos casette to generate the new plasmid, pLAFR5. This latter cosmid simplifies vector preparation and has permitted the rapid cloning of genomic DNA fragments generated with Sau3A. The resulting clones may be introduced into other Gram-negative bacteria by conjugation.

Amino Acid Sequence↗
PubMed2004

Analysis of host range phenotypes of primate hepadnaviruses by in vitro infections of hepatitis D virus pseudotypes.

Hepatitis B virus (HBV) and woolly monkey hepatitis B virus (WMHBV) have natural host ranges that are limited to closely related species. The barrier for infection of primates seems to be at the adsorption and/or entry steps of the viral replication cycle, since a human hepatoma cell line is permissive for HBV and WMHBV replication following transfection of cloned DNA. We hypothesized that the HBV and WMHBV envelope proteins contain the principal viral determinants of host range. As previously shown by using the hepatitis D virus (HDV) system, recombinant HBV-HDV particles were infectious in chimpanzee as well as human hepatocytes. We extended the HDV system to include HDV particles pseudotyped with the WMHBV envelope. In agreement with the natural host ranges of HBV and WMHBV, in vitro infections demonstrated that HBV-HDV and WM-HDV particles preferentially infected human and spider monkey cells, respectively. Previous studies have implicated the pre-S1 region of the large (L) envelope protein in receptor binding and host range; therefore, recombinant HDV particles were pseudotyped with the hepadnaviral envelopes containing chimeric L proteins with the first 40 amino acids from the pre-S1 domain exchanged between HBV and WMHBV. Surprisingly, addition of the human amino terminus to the WMHBV L protein increased infectivity on spider monkey hepatocytes but did not increase infectivity for human hepatocytes. Based upon these data, we discuss the possibility that the L protein may be comprised of two domains that affect infectivity and that sequences downstream of residue 40 may influence host range and receptor binding or entry.

Amino Acid Sequence↗
PubMed1984

Host specificity and host range of the genus Sarcocystis in three snake-rodent life cycles.

Three Sarcocystis species with snake-rodent life cycles were studied for their host range and host specificity in systematically related intermediate and definitive hosts. While S. singaporensis and S. villivillosi developed only in murids closely related to the genus Rattus, a third Sarcocystis species (natural definitive host: Bitis nasicornis - syn. Isospora dirumpens ?) showed a broad intermediate host range. This species was found to use several Bitis species as definitive hosts. S. singaporensis and S. villivillosi in contrary produced sporocysts only in three Python species and in Aspidites melanocephalus .

Animals↗
PubMed2000

Host range and variability of calcium binding by surface loops in the capsids of canine and feline parvoviruses.

Canine parvovirus (CPV) emerged in 1978 as a host range variant of feline panleukopenia virus (FPV). This change of host was mediated by the mutation of five residues on the surface of the capsid. CPV and FPV enter cells by endocytosis and can be taken up by many non-permissive cell lines, showing that their host range and tissue specificity are largely determined by events occurring after cell entry. We have determined the structures of a variety of strains of CPV and FPV at various pH values and in the presence or absence of Ca(2+). The largest structural difference was found to occur in a flexible surface loop, consisting of residues 359 to 375 of the capsid protein. This loop binds a divalent calcium ion in FPV and is adjacent to a double Ca(2+)-binding site, both in CPV and FPV. Residues within the loop and those associated with the double Ca(2+)-binding site were found to be essential for virus infectivity. The residues involved in the double Ca(2+)-binding site are conserved only in FPV and CPV. Our results show that the loop conformation and the associated Ca(2+)-binding are influenced by the Ca(2+) concentration, as well as pH. These changes are correlated with the ability of the virus to hemagglutinate erythrocytes. The co-localization of hemagglutinating activity and host range determinants on the virus surface implies that these properties may be functionally linked. We speculate that the flexible loop and surrounding regions are involved in binding an as yet unidentified host molecule and that this interaction influences host range.

Amino Acid Substitution↗
PubMed1998

Comparison of field-collected ascovirus isolates by DNA hybridization, host range, and histopathology.

Six field-collected ascovirus isolates obtained from five noctuid species in the continental United States were compared with respect to the general relatedness of their DNA, host range, and histopathology. Two isolates were from Spodoptera frugiperda, and the other four were from Autographa precationis, Heliothis virescens, Helicoverpa zea, and Trichoplusia ni. DNA-DNA hybridization studies showed that the six isolates belonged to three distinct viral species, with the isolates from S. frugiperda composing one species, those from A. precationis and H. virescens a second species, and those from H. zea and T. ni a third species. The host range and histopathology of each isolate was studied in eight noctuid species, S. frugiperda, Spodoptera ornithogalli, Spodoptera exigua, Spodoptera eridania, H. virescens, H. zea, A. precationis, and Feltia subterranea. Though some variation existed between the different isolates of each viral species, distinct patterns were apparent for each. The viral species from S. frugiperda had a host range that was limited primarily to Spodoptera species and both isolates of this virus only replicated and caused significant pathology in the fat body, whereas the viral species from A. precationis and H. virescens had a much broader host range that included most of the species tested, but also had a tissue tropism primarily restricted to the fat body. The viral species from T. ni and H. zea readily infected all the hosts tested, where the principal site of replication and significant pathology was the epidermis. In many test hosts, however, this viral species also replicated and caused significant pathology in the tracheal epithelium and to a lesser extent in the fat body. Aside from contributing to knowledge of ascovirus biology, these studies indicate that DNA hybridization profiles combined with studies of host range and tissue tropism can be used as characters for defining ascovirus species.

Animals↗
PubMed1984

Analysis of the trfA region of broad host-range plasmid RK2 by transposon mutagenesis and identification of polypeptide products.

Broad host-range plasmid RK2 is a member of the Escherichia coli incompatibility group P. Unlike most other groups of plasmids, members of the P group are capable of efficient transfer between and maintenance in most gram-negative bacterial species. It is of interest whether this broad host-range results from differences between the mechanism of replication of broad and narrow host-range plasmids. The regions of RK2 required for replication in E. coli have previously been defined as an origin of vegetative replication, oriVRK2 , and a gene, trfA , specifying a positively required trans-acting product. In this study Tn1723 transposon insertions have been used to map the trfA gene and determine its functional gene product. The Tn1723 insertions define the outer limits of the gene, a promoter region, a "leader" region not essential for trfA activity and a coding region. Three polypeptides of 13 X 10(3), 43 X 10(3) and 32 X 10(3) molecular weight are produced from this region and the production of a 32 X 10(3) Mr polypeptide is shown to be correlated with trfA activity in E. coli. Analysis of polypeptides produced from transposon insertion derivatives in which all but 35 base-pairs of inserted DNA is deleted, along with the effect of these insertions on trfA activity, suggest that the 43 X 10(3) and 32 X 10(3) Mr polypeptide coding sequences overlap in the same reading frame and that all three polypeptides (13 X 10(3), 32 X 10(3) and 43 X 10(3) Mr) may be translated from the same initial transcript.

Chromosome Mapping↗
PubMed1978

Serological studies of a host range mutant of a lactic streptococcal bacteriophage.

A host range mutant was isolated from a bacteriophage that attacked Streptococcus cremoris 114. The mutant was able to adsorb and grow on S. cremoris 266, where the parent phage could not. The mutant phage was unable to adsorb to the original bacterial host, S. cremoris 114. The change in host range was accompanied by an alteration in the neutralization antigen as shown by a change in neutralization rate by an anti-phage serum. Serum-blocking experiments confirmed the difference in neutralization antigen between parent and mutant phages. The two phages nevertheless had similar complement fixation antigens, confirming that one was a mutant derived from the other. A distinction between complement fixation and neutralization antigens, similar to that found for the coliphages and staphylococcal phages, has therefore been demonstrated for two lactic streptococcal phages.

Adsorption↗