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PubMed1983

Activity of the hybrid trp-lac (tac) promoter of Escherichia coli in Pseudomonas putida. Construction of broad-host-range, controlled-expression vectors.

A broad-host-range vector, pKT240, containing the structural gene (aph) for aminoglycoside phosphotransferase (APH), without promoter, has been constructed. Insertion of DNA fragments carrying promoters upstream of aph gene into the unique EcoRI site of this vector results in the expression of the aph gene and consequently the resistance of the host cells to streptomycin. The new vector has been used to show that the hybrid trp-lac (tac) promoter and the promoter of the lacIQ gene of Escherichia coli are active in Pseudomonas putida. Derivatives of pKT240 containing tac and lacIQ sequences may be used as wide-host-range expression vectors. Regulated overproduction of APH and catechol 2,3-oxygenase can be obtained with the aid of the new vectors in both E. coli and P. putida.

Catechol 2,3-Dioxygenase↗

PubMed2000

Interactions of DnaA proteins from distantly related bacteria with the replication origin of the broad host range plasmid RK2.

Replication initiation of the broad host range plasmid RK2 requires binding of the host-encoded DnaA protein to specific sequences (DnaA boxes) at its replication origin (oriV). In contrast to a chromosomal replication origin, which functionally interacts only with the native DnaA protein of the organism, the ability of RK2 to replicate in a wide range of Gram-negative bacterial hosts requires the interaction of oriV with many different DnaA proteins. In this study we compared the interactions of oriV with five different DnaA proteins. DNase I footprint, gel mobility shift, and surface plasmon resonance analyses showed that the DnaA proteins from Escherichia coli, Pseudomonas putida, and Pseudomonas aeruginosa bind to the DnaA boxes at oriV and are capable of inducing open complex formation, the first step in the replication initiation process. However, DnaA proteins from two Gram-positive bacteria, Bacillus subtilis and Streptomyces lividans, while capable of specifically interacting with the DnaA box sequences at oriV, do not bind stably and fail to induce open complex formation. These results suggest that the inability of the DnaA protein of a host bacterium to form a stable and functional complex with the DnaA boxes at oriV is a limiting step for plasmid host range.

Amino Acid Sequence↗

PubMed1989

Structural and functional analysis of nitrogenase genes from the broad-host-range Rhizobium strain ANU240.

The genes encoding the structural components of nitrogenase, nifH, nifD and nifK, from the fast-growing, broad-host-range Rhizobium strain ANU240 have been identified and characterized. They are duplicated and linked in an operon nifHDK in both copies. Sequence analysis of the nifH gene from each copy, together with partial sequence analysis of the nifD and nifK genes, and restriction endonuclease analysis suggested that the duplication is precise. Comparison of the Fe-protein sequence from strain ANU240 with that from other nitrogen-fixing organisms revealed that, despite its broad host range and certain physiological properties characteristic of Bradyrhizobium strains, ANU240 is more closely related to the narrow-host-range Rhizobium strains than to the broad-host-range Bradyrhizobium strains. The promoter regions of both copies of the nif genes contain the consensus sequence characteristic of nif promoters, and functional analysis of the two promoters suggested that both nif operons are transcribed in nodules.

Amino Acid Sequence↗

PubMed1991

Point substitution in a promoter-like region and the V1 gene affect the host range and symptoms of maize streak virus.

The nucleotide sequences of full-length infectious clones of two symptomatic and host range variants (MSV-Ns and MSV-Nm) of the Nigerian strain of maize streak virus (MSV) have been determined and shown to differ by only three nucleotides. MSV-Ns produced symptoms in infected maize plants sooner and the streaks were wider and more chlorotic than those of MSV-Nm; variant MSV-Ns also had a wider host range within the Gramineae. None of the three nucleotide differences resulted in amino acid changes. Site-directed mutagenesis showed that a substitution at nucleotide (nt) 40 in the V1 gene affected streak width, while severity of chlorosis, length of streaks, latency, and host range was determined by a single base change at nt 2473 in the large intergenic region. The nt 2473 change altered a potential promoter sequence (TATA box) in MSV-Ns 101 nucleotides upstream of the initiation codon of the C1 gene. Mutagenesis of TATA sequences located downstream of TATA -101 showed that TATA -101 alone was sufficient to confer a wide host range phenotype on MSV-Ns and suggested that it might function as a promoter for the expression of complementary-sense open reading frames. When compared with an updated promoter consensus derived from genes of the Gramineae, the promoter context around TATA -101 in MSV-Ns was not more favorable than those found at -57 and -62 in MSV-Nm.

Base Sequence↗

PubMed1998

Prevalence of broad-host-range lytic bacteriophages of Sphaerotilus natans, Escherichia coli, and Pseudomonas aeruginosa.

Two bacteriophage collections were examined with regard to their ability to form plaques on multiple bacterial host species. Nine of 10 phages studied were found to be broad-host-range bacteriophages. These phages fell into two groups. Group 1, the SN series, was isolated from sewage treatment plant samples with Sphaerotilus natans ATCC 13338 as a host. The DNAs of these bacteriophages contained modified bases and were insensitive to cleavage by type I and II restriction endonucleases. The efficiency of plating of these bacteriophages was changed only slightly on the alternate host. Group 2, the BHR series, was isolated by a two-host enrichment protocol. These bacteriophages were sensitive to restriction, and their efficiency of plating was dramatically reduced on the alternate host. Our results suggest that a multiple-host enrichment protocol may be more effective for the isolation of broad-host-range bacteriophages by avoiding the selection bias inherent in single-host methods. At least two of the broad-host-range bacteriophages mediated generalized transduction. We suggest that broad-host-range bacteriophages play a key role in phage ecology and gene transfer in nature.

Bacteriophages↗

PubMed1985

Specific-purpose broad-host-range vectors.

Several plasmid derivatives of broad-host-range Inc P4 plasmid RSF1010 were constructed and characterized. Vector pAYC30 was constructed by insertion in vivo into the genome of RSF1010 the Hgr transposon Tn501, originating from the plasmid pVS1 of Pseudomonas aeruginosa. Plasmids with inserts of PstI or SacI fragments may be selected by inactivation of genes sul and aph, respectively. The cloning at unique site SalGI leads to the appearance of HgCl2--sensitive transformants. Versatile cloning vector pAYC1 consists of two replicons, RSF1010 and plasmid pMZ7, a derivative of R6K. The constructed plasmid is 16.9 kb in length and determines resistance to five drugs. Two promoter-probe broad-host-range vectors, pAYC36 and pAYC37, were obtained by replacing a small segment from the DNA sequence of the aph gene promoter of previously described plasmid pAYC32 with the polylinker from plasmid pUC19. Therefore, vector plasmids retained the intact gene aph (Smr); however, they have Sms phenotype because of the insertional inactivation of the promoter. The genetic structure of promoter-probe vectors allows one to select clones, containing hybrid plasmids with an active promoter for gene aph expression.

Chromosome Mapping↗

PubMed2006

Virulence of broad- and narrow-host-range Salmonella enterica serovars in the streptomycin-pretreated mouse model.

Salmonella enterica subspecies I serovars are common bacterial pathogens causing diseases ranging from enterocolitis to systemic infections. Some serovars are adapted to specific hosts, whereas others have a broad host range. The molecular mechanisms defining the virulence characteristics and the host range of a given S. enterica serovar are unknown. Streptomycin pretreated mice provide a surrogate host model for studying molecular aspects of the intestinal inflammation (colitis) caused by serovar Typhimurium (S. Hapfelmeier and W. D. Hardt, Trends Microbiol. 13:497-503, 2005). Here, we studied whether this animal model is also useful for studying other S. enterica subspecies I serovars. All three tested strains of the broad-host-range serovar Enteritidis (125109, 5496/98, and 832/99) caused pronounced colitis and systemic infection in streptomycin pretreated mice. Different levels of virulence were observed among three tested strains of the host-adapted serovar Dublin (SARB13, SD2229, and SD3246). Several strains of host restricted serovars were also studied. Two serovar Pullorum strains (X3543 and 449/87) caused intermediate levels of colitis. No intestinal inflammation was observed upon infection with three different serovar Paratyphi A strains (SARB42, 2804/96, and 5314/98) and one serovar Gallinarum strain (X3796). A second serovar Gallinarum strain (287/91) was highly virulent and caused severe colitis. This strain awaits future analysis. In conclusion, the streptomycin pretreated mouse model can provide an additional tool to study virulence factors (i.e., those involved in enteropathogenesis) of various S. enterica subspecies I serovars. Five of these strains (125109, 2229, 287/91, 449/87, and SARB42) are subject of Salmonella genome sequencing projects. The streptomycin pretreated mouse model may be useful for testing hypotheses derived from this genomic data.

Animals↗

PubMed1988

Characterization of a pantropic variant of Sendai virus derived from a host range mutant.

A variant (F1-R) was isolated from a temperature-sensitive host range mutant (ts-f1) of Sendai virus. F1-R was no longer temperature-sensitive but it retained the host range phenotype. Unlike wild-type virus, F1-R and ts-f1 undergo multiple cycles of replication in several cell lines in the absence of trypsin. This was attributed to proteolytic activation of the fusion (F) glycoprotein of the host range mutants, in cell nonpermissive to wild-type virus. In mice infected intranasally the variant F1-R caused a generalized infection. This was shown by immunohistology and with infectious virus being recovered from several organs whereas infection with wild-type virus was restricted to the lung. These observations indicate that the pantropic property of F1-R is the result of proteolytic activation of the virus by ubiquitous proteases. Nucleotide sequence analyses revealed that ts-f1 and F1-R differed from the wild-type virus by mutations at the region of the cleavage site of F and at the glycosylation site of the F2 subunit. The findings indicated that these mutations are responsible for the increased cleavability of the F protein of ts-f1 and F1-R and therefore are important determinants for the pantropism of F1-R.

Animals↗

PubMed1995

Comparison of the in vitro host range of recombinant met-interferon-con1, interferon-alpha 2b, and interferon-beta [corrected].

The antiviral activity of human r-metIFN-con1 was compared with that of IFN-alpha 2b and IFN-beta on a number of human, other primate, rodent, feline, and canine cell lines. Although the specific activities of r-metIFN-con1 and IFN-alpha 2b differed 10-fold, the host range was very similar. The host range of IFN-beta differed from that of r-metIFN-con1 and IFN-alpha 2b in that Vero cells were 100-fold better protected by IFN-beta and MDBK protected at a 100-fold less efficiency. In general, there were only minor differences between the host ranges of the three interferons, human and primate cells being better protected than those of other species. However, the tissue of origin of the cell appears to be more important than the species of origin in defining host range [corrected].

Animals↗

PubMed2002

Host-specific incompatibility by 9-bp direct repeats indicates a role in the maintenance of broad-host-range plasmid RK2.

Broad-host-range incompatibility group P (IncP) plasmids RK2 and R751 have 9-bp direct repeats (DR) of unknown function located between their kilC and kilE loci. The nucleotide sequences of the 9-bp repeats are different for RK2 (an IncPalpha group plasmid) and R751 (IncPbeta group), but both DR regions are organized similarly, including an 11-bp spacer with identical 5'-CGCCA-3' cores and an adjacent binding site for KorB, a known partition protein and transcriptional repressor. The occurrence of similarly arranged DR elements with different repeat sequences is suggestive of an important plasmid-specific function for the DR regions. Here we show that the cloned RK2 DR region in trans to RK2 exhibits a host-specific incompatibility phenotype, in which RK2 is destabilized in Pseudomonas aeruginosa but not in Escherichia coli. Incompatibility was not dependent on the adjacent KorB-binding site. Deletion of the kilE locus, which is required for stable maintenance in P. aeruginosa, did not abolish DR-mediated incompatibility. Precise deletion of DR from RK2 had no effect on maintenance but eliminated sensitivity to DR in trans, showing that incompatibility requires DR to be present on both plasmids. These results raise the possibility that the DR region may be involved in a plasmid maintenance system for P. aeruginosa that is independent of the known stability functions on RK2.

Bacterial Proteins↗

PubMed1990

Vaccinia virus host range genes.

A gene encoding an 18-kDa polypeptide (ORF C7L) located in the vaccinia virus HindIII C fragment was shown to be functionally equivalent to previously described host range gene (ORF K1L) spanning the HindIII K/M fragment junction. Either C7L or K1L host range gene is necessary and sufficient by itself to allow replication of vaccinia virus on human cells. Deletion of both C7L and K1L genes from the wild-type vaccinia genome is required to derive a virus deficient for replication on human cells. Further, an ORF encoding a 77-kDa polypeptide derived from cowpox (CP77kDa) and previously shown to allow vaccinia to overcome the restriction for replication on Chinese hamster ovary cells could substitute for the vaccinia host range genes C7L and K1L in permitting replication of the virus on human cells. Additionally, the three unique host range genes C7L, K1L, and CP77kDa were functionally equivalent for vaccinia replication on pig kidney cells, but not on rabbit kidney cells.

Animals↗

PubMed1984

Proteins encoded by the trans-acting replication and maintenance regions of broad host range plasmid RK2.

The broad host range plasmid RK2 has previously been found to contain three separate regions of the genome involved in replication and maintenance in Escherichia coli (C. M. Thomas, R. Meyer, D. R. Helinski, 1980, J. Bacteriol. 141, 213-222). They include the origin of replication (oriRK2) and the trfA region which encodes a trans-acting function required for replication. The third region (trfB), although not essential for replication, supplies a function involved in the maintenance of plasmid RK2. Using the maxicell system of labeling plasmid-specific proteins, we have identified all of the proteins encoded by two miniplasmid derivatives of RK2 which contain only the regions oriRK2, trfA, and trfB. To determine which region specifies each protein, RK2/mini-ColE1 hybrid plasmids were used which contain various restriction fragments of the mini-RK2 replicon. The trfA region appears to encode three proteins designated A1 (39,000 MW), A2 (31,000 MW), and A3 (14,000 MW). Analysis of proteins synthesized by plasmids containing deleted forms of the trfA region indicates that the A2 protein is the essential trfA-encoded replication protein of plasmid RK2. The proteins A1 and A3 may be the products specified by the genes tra3 (involved in transmissibility) and kilB1 (involved in host-cell viability) which also map in the trfA region. The trfB region specifies two proteins designated B1 (36,000 MW) and B2 (30,000 MW). These may be the products of the two kil-override (kor) genes located in the trfB region which have been implicated in plasmid maintenance.

Bacterial Proteins↗

PubMed2005

Sialobiology of influenza: molecular mechanism of host range variation of influenza viruses.

The gene pool of influenza A viruses in aquatic birds provides all of the genetic diversity required for human and lower animals. Host range selection of the receptor binding specificity of the influenza virus hemagglutinin occurs during maintenance of the virus in different host cells that express different receptor sialo-sugar chains. In this paper, functional roles of the hemagglutinin and neuraminidase spikes of influenza viruses are described in the relation to 1) host range of influenza viruses, 2) receptor binding specificity of human and other animal influenza viruses, 3) recognition of sialyl sugar chains by Spanish influenza virus hemagglutinin, 4) highly pathogenic and potentially pandemic H5N1, H9N2, and H7N7 avian influenza viruses and molecular mechanism of host range variation of influenza viruses, 5) role of the neuraminidase spike for the host range of influenza viruses, and 6) Development of anti-influenza drugs.

Animals↗

PubMed2006

Cooperative involvement of the S1 and S2 subunits of the murine coronavirus spike protein in receptor binding and extended host range.

To study the process of spike (S)-receptor interaction during coronavirus entry, we evaluated the contributions of mutations in different regions of the murine hepatitis virus (MHV) S protein to natural receptor murine carcinoembryonic antigen-related cell adhesion molecule 1a (CEACAM1a) dependence and to the acquisition of extended host range. Extended-host-range variants of MHV strain A59 were previously obtained from persistently infected cells (J. H. Schickli, B. D. Zelus, D. E. Wentworth, S. G. Sawicki, and K. V. Holmes, J. Virol. 71:9499-9504, 1997). These variant viruses contain several mutations in the S protein that confer to the viruses the ability to enter cells in a heparan sulfate-dependent manner (C. A. de Haan, Z. Li, E. te Lintelo, B. J. Bosch, B. J. Haijema, and P. J. M. Rottier, J. Virol. 79:14451-14456, 2005). While the parental MHV-A59 is fully dependent on murine CEACAM1a for its entry, viruses carrying the variant mutations in the amino-terminal part of their S protein had become dependent on both CEACAM1a and heparan sulfate. Substitutions in a restricted, downstream part of the S protein encompassing heptad repeat region 1 (HR1) and putative fusion peptide (FP) did not alter the CEACAM1a dependence. However, when the mutations in both parts of the S protein were combined, the resulting viruses became independent of CEACAM1a and acquired the extended host range. In addition, these viruses showed a decreased binding to and inhibition by soluble CEACAM1a. The observations suggest that the amino-terminal region of the S protein, including the receptor-binding domain, and a region in the central part of the S protein containing HR1 and FP, i.e., regions far apart in the linear sequence, communicate and may even interact physically in the higher-order structure of the spike.

Amino Acid Substitution↗

PubMed1976

Outer membrane of Escherichia coli K-12: isolation of mutants with altered protein 3A by using host range mutants of bacteriophage K3.

A series of mutants has been isolated with alterations to protein 3A of the outer membrane. These mutations map at the previously described con locus as shown by cotransduction with pyrD. Most of them do not have detectable levels of protein 3A but are thought to have low levels of altered protein. These mutants have been detected by screening con mutants, isolated as resistant to bacteriophage K3, for their ability to plaque host range mutants of this bacteriophage. These host range phage mutants have activity spectra on the various con mutants that enable the bacterial mutants to be arranged in an order of increasing resistance to the host range phage mutants, from mutants sensitive to all host range phage to those sensitive to only one class. Likewise, the phage can be arragned in an order of increasing ability to plaque on the con mutants. Some of the mutants resemble the previously described con mutants in being tolerant to colicins K and L, and others resemble them in being highly defective as recipients with the F factor. These properties vary independently, suggesting that protein 3A can be modified to independently affect the three properties of bacteriophage receptor function, involvement in colicin sensitivity, and involvement in conjugation.

Bacterial Proteins↗

PubMed1984

Analysis of copy number control elements in the region of the vegetative replication origin of the broad host range plasmid RK2.

Broad host-range plasmid RK2 is able to replicate in a controlled manner in most Gram negative bacterial species. To analyze the elements of its control mechanism, we have measured the copy number in Escherichia coli of mini-RK2 replicons isogenic except for defined deletions in regions adjacent to the vegetative replication origin, oriVRK2, which have previously been implicated in copy number control because of their expression of plasmid incompatibility. The results indicate that while the previously defined 700-bp HaeII oriVRK2 fragment carries one copy control element (copA), a second (copB) lies at least partly outside this fragment towards the tetracycline resistance genes of RK2. Deletions affecting both these regions give a mini replicon with a copy number of 35-40 compared with 4-7 for parental RK2. Further incompatibility experiments indicate that targets for both incA (copA) and incB (copB) lie within the 700-bp HaeII oriVRK2 fragment.

Base Sequence↗

PubMed1998

A novel expression system based on host-range expansion of baculovirus.

A host range expanded recombinant Autographa californica multiple-nucleocapsid nucleopolyhedrosis virus AcMNPV/r2 was obtained by cotransfection of the bacmid DNA from Escherichia coli DH10Bac along with a plasmid pBmH-M containing HindIII M fragment of Bombyx mori nuclear polyhedrosis virus (BmNPV) genomic DNA. A recombinant transposon vector carrying a mutant green fluorescent protein gene (GFP) and a polyhedrin gene was constructed. Transposition was carried out in both E. coli DH10Bac and E. coli DH10BmH, which contains AcMNPV/r2 and a helper plasmid. Recombinant DNAs were transfected into Sf-9 cells to generate recombinant virus AcMNPV/r3 and AcMNPV/r4 respectively. Viral stock of AcMNPV/r4 was then infected into Bombyx mori cells (BmN) and Bombyx mori larvae (silkworm). Analysis shows that GFP was highly expressed in Bombyx mori larvae. This expression system, is practicable therefore for mass production of foreign gene products.

Animals↗

PubMed1992

DnaG-dependent priming signals can substitute for the two essential DNA initiation signals in oriV of the broad host-range plasmid RSF1010.

Broad host-range plasmid RSF1010 contains in the oriV region two DNA initiation signals, ssiA(RSF1010) and ssiB(RSF1010), which are essential for plasmid replication. Each of ssiA and ssiB could be substituted functionally by either of the two G4-type (DnaG-dependent) priming signals, the oric of bacteriophage G4 and an ssi signal from plasmid pSY343 (an R1 plasmid derivative). Functions of the chimeric oriVs of RSF1010 thus constructed were dependent on the RSF1010-specific replication proteins, RepA, RepB' and RepC. When both of ssiA and ssiB were replaced by the G4-type ssi signals, functions of the chimeric oriVs were no longer dependent on RepB' (RSF1010-specific DNA primase). The replication activities of the chimeric oriVs of RSF1010 were not influenced markedly by the type of heterologous priming signals they contained. It is conceivable that DNA replication of RSF1010 does not need the priming mechanism for lagging strand synthesis and proceeds by the strand displacement mechanism.

Bacterial Proteins↗