New bacteriophage of Haemophilus influenzae

Interactions of Bacteriophages and Bacteria at the Airway Mucosa: New Insights Into the Pathophysiology of Asthma

The airway epithelium is the primary site where inhaled and resident microbiota interacts between themselves and the host, potentially playing an important role on allergic asthma development and pathophysiology. With the advent of culture independent molecular techniques and high throughput technologies, the complex composition and diversity of bacterial communities of the airways has been well-documented and the notion of the lungs' sterility definitively rejected. Recent studies indicate that the microbial composition of the asthmatic airways across the spectrum of disease severity, differ significantly compared with healthy individuals. In parallel, a growing body of evidence suggests that bacterial viruses (bacteriophages or simply phages), regulating bacterial populations, are present in almost every niche of the human body and can also interact directly with the eukaryotic cells. The triptych of airway epithelial cells, bacterial symbionts and resident phages should be considered as a functional and interdependent unit with direct implications on the respiratory and overall homeostasis. While the role of epithelial cells in asthma pathophysiology is well-established, the tripartite interactions between epithelial cells, bacteria and phages should be scrutinized, both to better understand asthma as a system disorder and to explore potential interventions.

Complete nucleotide sequence of a P2 family lysogenic bacteriophage, ϕMhaA1-PHL101, from Mannheimia haemolytica serotype A1

The 34,525 nucleotide sequence of a double-stranded DNA bacteriophage (phiMhaA1-PHL101) from Mannheimia haemolytica serotype A1 has been determined. The phage encodes 50 open reading frames. Twenty-three of the proteins are similar to proteins of the P2 family of phages. Other protein sequences are most similar to possible prophage sequences from the draft genome of Histophilus somni 2336. Fourteen open reading frames encode proteins with no known homolog. The P2 orthologues are collinear in phiMhaA1-PHL101, with the exception of the phage tail protein gene T, which maps in a unique location between the S and V genes. The phage ORFs can be arranged into 17 possible transcriptional units and many of the genes are predicted to be translationally coupled. Southern blot analysis revealed phiMhaA1-PHL101 sequences in other A1 isolates as well as in serotype A5, A6, A9, and A12 strains of M. haemolytica, but not in the related organisms, Mannheimia glucosida or Pasteurella trehalosi.

Cloning and sequencing of a genomic island found in the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius

A genomic island was identified in the Haemophilus influenzae biogroup aegyptius Brazilian purpuric fever (BPF) strain F3031. This island, which was also found in other BPF isolates, could not be detected in non-BPF biogroup aegyptius strains or in nontypeable or typeable H. influenzae strains, with the exception of a region present in the type b Eagan strain. This 34,378-bp island is inserted, in reference to H. influenzae Rd KW20, within a choline transport gene and contains a mosaic structure of Mu-like prophage genes, several hypothetical genes, and genes potentially encoding an Erwinia carotovora carotovoricin Er-like bacteriocin. The product of the tail fiber ORF in the bacteriocin-like region shows a hybrid structure where the C terminus is similar to an H. influenzae phage HP1 tail protein implicating this open reading frame in altering host specificity for a putative bacteriocin. Significant synteny is seen in the entire genomic island with genomic regions from Salmonella enterica subsp. enterica serovar Typhi CT18, Photorhabdus luminescens subsp. laumondii TT01, Chromobacterium violaceum, and to a lesser extent Haemophilus ducreyi 35000HP. In a previous work, we isolated several BPF-specific DNA fragments through a genome subtraction procedure, and we have found that a majority of these fragments map to this locus. In addition, several subtracted fragments generated from an independent laboratory by using different but related strains also map to this island. These findings underscore the importance of this BPF-specific chromosomal region in explaining some of the genomic differences between highly invasive BPF strains and non-BPF isolates of biogroup aegyptius.

Bacteriophage HP2 of Haemophilus influenzae

Temperate bacteriophages effect chromosomal evolution of their bacterial hosts, mediating rearrangements and the acquisition of novel genes from other taxa. Although the Haemophilus influenzae genome shows evidence of past phage-mediated lateral transfer, the phages presumed responsible have not been identified. To date, six different H. influenzae phages are known; of these, only the HP1/S2 group, which lyosogenizes exclusively Rd strains (which were originally encapsulated serotype d), is well characterized. Phages in this group are genetically very similar, with a highly conserved set of genes. Because the majority of H. influenzae strains are nonencapsulated (nontypeable), it is important to characterize phages infecting this larger, genetically more diverse group of respiratory pathogens. We have identified and sequenced HP2, a bacteriophage of nontypeable H. influenzae. Although related to the fully sequenced HP1 (and even more so to the partially sequenced S2) and similar in genetic organization, HP2 has a few novel genes and differs in host range; HP2 will not infect or lysogenize Rd strains. Genomic comparisons between HP1/S2 and HP2 suggest recent divergence, with new genes completely replacing old ones at certain loci. Sequence comparisons suggest that H. influenzae phages evolve by recombinational exchange of genes with each other, with cryptic prophages, and with the host chromosome.

On the nature of nontypable Haemophilus influenzae

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.

Inhibition of transformation and transfection in Haemophilus influenzae Rd9 by lysogeny

Haemophilus influenzae Rd9 lysogenic for temperate bacteriophage N3 was found to be virtually nontransformable and nontransfectable. This inhibition of transformation and transfection was due partly to the decreased capacity of competent lysogenic cells for irreversible binding of deoxyribonucleic acid (DNA) and partly to some events taking place after adsorption of the DNA. The unadsorbed DNA was not degraded by the competent lysogenic cells.

Bacteriophage N3 of Haemophilus influenzae. I. Independence of vegetative recombination among Haemophilus influenzae bacteriophage on the host cell

Vegtative recombination of temperature-sensitive mutants of Haemophilus influezae bacteriophage N3 was measured in wild-type H. influenzae strain Rd9 and in recombination-defective mutants of the Rd strain. Recombinants are formed with low but equal frequency in wild-type cells and recombination-defective mutants of the Rd strain. It is concluded that this phage can carry information in its own genome for vegetative recombination. Lysogenization readily takes place in both strains.

Physical size of the donor locus and transmission of Haemophilus influenzae ampicillin resistance genes by deoxyribonucleic acid-mediated transformation

The properties of donor deoxyribonucleic acid (DNA) from three clinical isolates and its ability to mediate the transformation of competent Rd strains to ampicillin resistance were examined. A quantitative technique for determining the resistance of individual Haemophilus influenzae cells to ampicillin was developed. When this technique was used, sensitive cells failed to tolerate levels of ampicillin greater than 0.1 to 0.2 mug/ml, whereas three resistant type b beta-lactamase-producing strains could form from the colonies in 1- to 3-mug/ml levels of the antibiotic. DNA extracted from the resistant strains elicited transformation of the auxotrophic genes in a multiply auxotrophic Rd strain. For two of the donors, transformation to ampicillin resistance occurred after the uptake of a single DNA molecule approximately 104-fold less frequently than transformation of auxotrophic loci and was not observed to occur at all with the third. The frequency of transformation to ampicillin resistance was two- to fivefold higher in strain BC200 (Okinaka and Barnhart, 1974), which was cured of a defective prophage. All three clinical ampicillin-resistant strains were poor recipients, but the presence of the ampicillin resistant genes in strain BC200 did not reduce its competence. Sucrose gradients of DNA from ampicillin-resistant transformants of BC200 and from the original ampicillin-resistant strains showed that: (i) all the DNA preparations had high molecular weights; (ii) donor activity for ampicillin resistance sedimented heterogeneously and in parallel with genome DNA up to the highest molecular weights observed (100 x 106 to 200 x 106); and (iii) genetic transformation of ampicillin resistance from strain BC200-amp90383 required the physical integrity of a linearly integrated segment of DNA having a molecular weight of about 25 x 106 to 30 x 106.

Bacteriophage of Haemophilus influenzae. 3. Morphology, DNA homology, and immunity properties of HPlcl, S2, and the defective bacteriophage from strain Rd

The phages HP1c1 and S2 and a defective phage of Haemophilus influenzae have been compared. The morphology of the phages and the mol wt of their DNAs are similar, although the defective phage appears to have a different tail plate region. Electron microscope observation indicates that the defective phage does not attach to the cell surface, and its DNA appears to lack cohesive ends. The homology of the DNAs of the phages has been measured by hydridization. DNA from the defective phage shows little or no homology with the other phage DNAs. HP1c1 and S2 DNAs show a high level of homology. Each of these phages can form plaques on lawns of the lysogen of the other phage but at reduced plating efficiencies, suggesting that the two phages have related but not identical immunity systems.