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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Competent Haemophilus influenzae Rd recipients, either as phage HP1 restricting (r+) or nonrestricting (r-) nonlysogens or defective lysogens, were exposed to deoxyribonucleic acids from various wild-type phage HP1 lysogenic H. influenzae serotype strains (non-encapsulated derivatives of serotypes a,b, c, d, and e), to DNA from lysogenic Haemophilus parahaemolyticus, and to DNA from modified and nonmodified phage HP1. Transformation of antibiotic resistance markers and of prophage markers in homospecific crosses was observed to be unaffected by the recipient restriction phenotype, whereas the transfection response was much reduced in r+ recipients. Heterospecific transformation of prophage markers was reduced by only 80 to 90%, whereas antibiotic resistance marker transformation was 1,000 to 10,000 times lower. Heterspecific transfection was at least 100 times lower than homospecific transfection in both r+ and r- recipients. The general conclusion is that neither class I nor class II restriction enzymes affect significantly the transformation efficiency in homospecific and heterospecific crosses. The efficiency of heterospecific transformation may depend mainly on the deoxyribonucleic acid homology in the genetic marker region.
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PMID:Restriction enzymes do not play a significant role in Haemophilus homospecific or heterospecific transformation. 18 96

193 Haemophilus cultures, including 71 nontypable H. influenzae isolates, were examined with respect to phage HP1 sensitivity, lysogeny for this and for other phages and for excretion of bacteriocins. Fifty of the 71 nontypable cultures were sensitive to phage HP1 but only three produced plaques. The other 47 isolates were thus probably not non-encapsulated derivatives of H. influenzae serotypes a, b, d, and e, which have discrete and characteristic phage HP1 restriction and modification systems, or serotype c which appears to be restriction negative. They could be derivatives of serotype f which does not give plaques with phage HP1. The nontypable three cultures that plated phage HP1 efficiently could be non-encapsulated serotype c derivatives. Fourteen of the phage HP1 insentitive non-typable cultures were found to be defectively lysogenic for this phage. Five of these were genetically transformed to wild type lysogens. Their phage produced plaques efficiently only on Rc strains and on a restriction-negative mutant of serotype d. These lysogenic nontypable isolates are thus modification (and restriction) negative and they are thus probably not nonencapsulated derivatives of serotypes a, b, d, e, or f. Fifty three of 56 serotype b cultures were found to excrete a bacteriocin, to which all other nonproducing Haemophilus cultures were more or less sensitive. The three restriction-negative nontypable H. influenzae cultures also excreted this bacteriocin but the other cultures listed did not do this. The tentative conclusion from this study is that nontypable H. influenzae isolates are probably not derivatives of the six known encapsulated strains.
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PMID:On the nature of nontypable Haemophilus influenzae. 31 83

The biological fate of temperate phage HP1 deoxyribonucleic acid (DNA) was followed after uptake by defectively lysogenic competent Haemophilus influenzae cultures. The similar inactivation kinetics of three single phage genetic markers and of their triple combination indicated a complete rather than partial destruction of about half of the adsorbed DNA molecules. Intracellular DNA breakdown products were tentatively identified by hydroxyapatite column chromatography as short single strands and extensively damaged short double strands. Integrated donor DNA (after single-strand insertion?) was still highly efficient for triple-marker co-transformation. This suggests that whole or nearly whole donor DNA molecules were integrated. Some donor DNA was never integrated but remained largely unaltered. This DNA fraction did not contain significant amounts of recipient prophage marker activity. It is concluded that it had not participated in some kind of reciprocal recombination event involving the recipient chromosome. Since very similar phage DNA marker inactivation rates were observed after adsorption by competent nonlysogenic recipients (transfection), the relationship between biological inactivation of adsorbed donor phage DNA and its integration in lysogenic recipients is not clear.
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PMID:Fate of transforming bacteriophage HP1 deoxyribonucleic acid in Haemophilus influenzae lysogens. 108 Jan 48

Plasmids containing DNA segments from the attachment region of phage HP1 were constructed and tested for the ability to replace the phage attachment site substrate in site-specific recombination reactions. The distance separating the boundaries of the functional site was 418 bp. Replacements within the 11-residue segment 5'-GGCGGTTATCG at the left boundary or within the 12-residue segment 5'-GGATTTTTTGAA at the right boundary abolished substrate activity. A segment of the 418-residue sequence preserves the integrity of an operon of three Haemophilus influenzae tRNA genes after HP1 insertion within the coding sequence.
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PMID:Site-specific integration of the Haemophilus influenzae bacteriophage HP1: location of the boundaries of the phage attachment site. 138 94

Isotopic transfer experiments and boundary replacement studies were used to define the size and cleavage points of the Haemophilus influenzae attB site for phage HP1 integration. The points of strand cleavage and transfer were separated by 5' extensions with a spacing or overlap region most probably 7 residues long. The complete HP1 attB site is included within an 18-base pair (bp) sequence surrounding the cleavage sites. The sequence of HP1 attB is remarkably symmetric. Two 8-bp inverted repeats surround the central residue of the 7-bp overlap sequence; this central residue is the second residue of the anticodon sequence of the H. influenzae tRNA(leu)(UUR) gene which contains attB, and this symmetric segment encodes the anticodon stem and loop.
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PMID:Site-specific integration of the Haemophilus influenzae bacteriophage HP1. Identification of the points of recombinational strand exchange and the limits of the host attachment site. 155 93

The specific DNA-binding protein integration host factor (IHF) of Escherichia coli stimulates the site-specific recombination reaction between the attP site of bacteriophage HP1 and the attB site of its host, Haemophilus influenzae, in vitro and also appears to regulate the expression of HP1 integrase. IHF interacts specifically with DNA segments containing the att sites and the integrase regulatory region, as judged by IHF-dependent retardation of relevant DNA fragments during gel electrophoresis. The locations of the protein-binding sites were identified by DNase I protection experiments. Three sites in the HP1 attP region bound IHF, two binding sites were present in the vicinity of the attB region, and one region containing three partially overlapping sites was present in the HP1 integrase regulatory segment. The binding sites defined in these experiments all contained sequences which matched the consensus IHF binding sequences first identified in the lambda attP region. An activity which stimulated the HP1 site-specific integration reaction was found in extracts of H. influenzae, suggesting that an IHF-like protein is present in this organism.
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PMID:Interaction of integration host factor from Escherichia coli with the integration region of the Haemophilus influenzae bacteriophage HP1. 220 32

The nucleotide sequence of the leftmost 2,363 base pairs of the HP1 genome, which includes the attachment site (attP) and the integration region, was determined. This sequence contained an open reading frame encoding a 337-residue polypeptide, which is a member of the integrase family of site-specific recombination proteins as judged by sequence comparison. The open reading frame was located immediately adjacent to the att site and was oriented so that initiation of translation would begin distal to the att site and end in its immediate vicinity. Expression of this DNA segment in Escherichia coli provided extracts which promoted site-specific recombination between plasmids containing cloned HP1 attP and Haemophilus influenzae attB sites. This recombination was directional, since no reaction was observed between plasmids containing attR and attL sites. The reaction was stimulated by the accessory protein integration host factor of E. coli. Evidence was also obtained that the integration host factor influenced the levels of HP1 integrase expression. The deduced amino acid sequence of HP1 integrase has remarkable similarity to that deduced for the integrase of coliphage 186.
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PMID:Nucleotide sequence and expression of the gene for the site-specific integration protein from bacteriophage HP1 of Haemophilus influenzae. 254 15

Plasmids were constructed which contain both attP and attB DNA segments derived from the insertion sites of the lysogenic bacteriophage HP1 and its host, Haemophilus influenzae. Similar plasmids containing the two junction segments (attL and attR regions) between the phage genome and the lysogenic host chromosome were also prepared. The formation of recombinant dimer plasmids was observed when attP-attB plasmids were propagated in Escherichia coli HB101 (recA), while plasmids containing the junction segments did not form recombinant dimers. Deletion of the phage DNA segment adjacent to the attP site from the attP-attB constructions eliminated detectable recombination, suggesting that this sequence contains the gene encoding the HP1 integrase. No plasmid recombination was observed in strains of E. coli defective in integration host factor. This suggests that integration host factor is important in the expression or activity of the system which produces the site-specific recombination of sequences derived from HP1 and H. influenzae. Further, it suggests that a protein functionally analogous to E. coli integration host factor may be present in H. influenzae.
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PMID:Site-specific recombination between cloned attP and attB sites from the Haemophilus influenzae bacteriophage HP1 propagated in recombination-deficient Escherichia coli. 264 98

Two Haemophilus influenzae Rd genes each complemented the pleiotropic defects of the recA-like mutation rec-1. One gene, fec, was isolated on a 3.6-kilobase-pair EcoRI restriction fragment by complementation of the Fec- phenotype of bacteriophage lambda. The other gene, rec, was identified on a 3.1-kilobase-pair EcoRI fragment by Southern hybridization by using recA-like gene probes from Erwinia carotovora and Pseudomonas aeruginosa PAO. In a rec-1 strain of H. influenzae, the cloned genes restored resistance to UV irradiation, transformation by chromosomal DNA, and spontaneous release of HP1 prophage to wild-type levels. The fec and rec genes were located on the cloned segments by insertion and deletion mutagenesis and subcloning. The restriction endonuclease cleavage maps of the two DNAs were similar but not identical. Southern hybridization demonstrated that the two EcoRI restriction fragments contained homologous DNA sequences, but a fec gene-specific probe was prepared. Each gene encoded a 38,000-dalton polypeptide.
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PMID:Two Haemophilus influenzae Rd genes that complement the recA-like mutation rec-1. 278 4

We present the first complete map of the Haemophilus influenzae genome, consisting of a detailed restriction map with a number of genetic loci. All of the ApaI, SmaI, and RsrII restriction sites (total of 45 sites) were mapped by Southern blot hybridization analysis of fragments separated by pulsed-field gel electrophoresis. Cloned genes were placed on the restriction map by Southern hybridization, and antibiotic resistance loci were also located by transformation with purified restriction fragments. The attachment site of the HP1 prophage was mapped. In addition, the number, locations, and orientations of the six rRNA operons in the H. influenzae chromosome were determined. The positions of conserved restriction sites in these rrn operons confirm that the direction of transcription is 16S to 23S, as in most other bacteria. The widely used strain BC200 appears to contain an unexpected 45-kilobase duplication.
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PMID:Organization of the Haemophilus influenzae Rd genome. 278 84


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