Characterization of group H streptococcal temperate bacteriophage phi 227

Isolation and Characterization of Antagonistic Activity of Some Streptomycetes and their Specific Actinophages from Soil

<b>Background and Objective:</b> Phages specific to actinomycetes are common, active in the soil and gladly detected. Soil streptomycetes are having antibiosis activities against numerous bacteria, fungi and plant viruses. Thus, this study was designed to isolate, purify and characterize some streptomycetes active against some microorganisms from soil followed by isolation of their specific phages. <b>Materials and Methods:</b> Antagonistic activities of these streptomycetes isolates were tested against <i>Bacillus subtilis</i>,<i> Pseudomonas</i> sp., <i>Serratia</i> sp. and <i>Aspergillus niger</i>. To confirm their biological characterization of the streptomycetes isolates under investigation, the 16SrRNA gene was also used. The presence of specific lysate actinophages in the soil samples were tested by spot test technique and then propagated and purified for further characterization. The morphology of the purified actinophages was determined by electron microscopy. <b>Results:</b> The five selected <i>Streptomyces</i> isolates having effective antagonistic activity were biologically and molecularly identified as <i>Streptomyces sclerogranulatus </i>(QQ06), <i>Streptomyces mutabilis </i>(QQ07), <i>Streptomyces heilongjiangensis </i>(QQ08), <i>Streptomyces sparsus </i>(QQ09) and <i>Streptomyces purpurascens </i>(QQ10) strains. Electron micrographs showed the presence of filamentous virus-like particles with lengths of 21.4×928.57, 25×750, 21.4×857.14, 21.4×885.7 and 21.4×857.14 nm specific to <i>Streptomyces</i> strains QQ06, QQ07, QQ08, QQ09 and QQ10, respectively and belong to the family Inoviridae. <b>Conclusion:</b> Phage of Inoviridae was considered as the first time against streptomycetes isolates, therefore, additional and advanced studies should be carried out at the level of molecular characterization.

Role of Neuraminidase-Producing Bacteria in Exposing Cryptic Carbohydrate Receptors for Streptococcus gordonii Adherence

Streptococcus gordonii is an early colonizer of the oral cavity. Although a variety of S. gordonii adherence mechanisms have been described, current dogma is that the major receptor for S. gordonii is sialic acid. However, as many bacterial species in the oral cavity produce neuraminidase that can cleave terminal sialic acid, it is unclear whether S. gordonii relies on sialic acid for adherence to oral surfaces or if this species has developed alternative binding strategies. Previous studies have examined adherence to immobilized glycoconjugates and identified binding to additional glycans, but no prior studies have defined the contribution of these different glycan structures in adherence to oral epithelial cells. We determined that the majority of S. gordonii strains tested did not rely on sialic acid for efficient adherence. In fact, adherence of some strains was significantly increased following neuraminidase treatment. Further investigation of representative strains that do not rely on sialic acid for adherence revealed binding not only to sialic acid via the serine-rich repeat protein GspB but also to β-1,4-linked galactose. Adherence to this carbohydrate occurs via an unknown adhesin distinct from those utilized by Streptococcus oralis and Streptococcus pneumoniae Demonstrating the potential biological relevance of binding to this cryptic receptor, we established that S. oralis increases S. gordonii adherence in a neuraminidase-dependent manner. These data suggest that S. gordonii has evolved to simultaneously utilize both terminal and cryptic receptors in response to the production of neuraminidase by other species in the oral environment.

The use of bacteriophages to biocontrol oral biofilms

Infections induced by oral biofilms include caries, as well as periodontal, and peri-implant disease, and may influence quality of life, systemic health, and expenditure. As bacterial biofilms are highly resistant and resilient to conventional antibacterial therapy, it has been difficult to combat these infections. An innovative alternative to the biocontrol of oral biofilms could be to use bacteriophages or phages, the viruses of bacteria, which are specific, non-toxic, self-proliferating, and can penetrate into biofilms. Phages for Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, Fusobacterium nucleatum, Lactobacillus spp., Neisseria spp., Streptococcus spp., and Veillonella spp. have been isolated and characterised. Recombinant phage enzymes (lysins) have been shown to lyse A. naeslundii and Streptococcus spp. However, only a tiny fraction of available phages and their lysins have been explored so far. The unique properties of phages and their lysins make them promising but challenging antimicrobials. The genetics and biology of phages have to be further explored in order to determine the most effective way of applying them. Studying the effect of phages and lysins on multispecies biofilms should pave the way for microbiota engineering and microbiota-based therapy.

Classification of 17 newly isolated virulent bacteriophages of Pseudomonas aeruginosa

Seventeen virulent bacteriophages specific to Pseudomonas aeruginosa strains were isolated by screening various environmental samples. These isolated bacteriophages were grouped based on results obtained from restriction fragment analysis of phage genomes, random amplification of polymorphic DNA (RAPD) typing, morphology observations under transmission electron microscope, and host range analysis. All 17 bacteriophages are double-stranded DNA viruses and can be divided into 5 groups based on DNA restriction profiles. A set of 10-mer primers was used in RAPD typing of phages, and similar conclusions were obtained as for restriction fragment analysis. One phage was randomly selected from each of the 5 groups for morphology observations. Four of them had an icosahedral head with a long contractile tail, belonging to the Myoviridae family, and one phage had an icosahedral head with a short tail, thereby belonging to the Podoviridae family. Host range experiments were conducted on 7 laboratory strains and 12 clinical strains of P. aeruginosa. The results showed that 13 phages had the same infection profile, killing 8 out of 19 tested P. aeruginosa strains, and the remaining 4 phages had different and unique infection profiles. This study highlights the diversity of bacteriophages specific to P. aeruginosa in the environment.

Isolation and characterization of a virulent bacteriophage AB1 of Acinetobacter baumannii

Background

Acinetobacter baumannii is an emerging nosocomial pathogen worldwide with increasing prevalence of multi-drug and pan-drug resistance. A. baumannii exists widely in natural environment, especially in health care settings, and has been shown difficult to be eradicated. Bacteriophages are often considered alternative agent for controlling bacterial infection and contamination. In this study, we described the isolation and characterization of one virulent bacteriophage AB1 capable of specifically infecting A. baumannii.

Results

A virulent bacteriophage AB1, specific for infecting a clinical strain A. baumannii KD311, was first isolated from marine sediment sample. Restriction analysis indicated that phage AB1 was a dsDNA virus with an approximate genome size of 45.2 kb to 46.9 kb. Transmission electron microscopy showed that phage AB1 had an icosahedral head with a non-contractile tail and collar or whisker structures, and might be tentatively classified as a member of the Siphoviridae family. Proteomic pattern of phage AB1, generated by SDS-PAGE using purified phage particles, revealed five major bands and six minor bands with molecular weight ranging from 14 to 80 kilo-dalton. Also determined was the adsorption rate of phage AB1 to the host bacterium, which was significantly enhanced by addition of 10 mM CaCl₂. In a single step growth test, phage AB1 was shown having a latent period of 18 minutes and a burst size of 409. Moreover, pH and thermal stability of phage AB1 were also investigated. At the optimal pH 6.0, 73.2% of phages survived after 60 min incubation at 50°C. When phage AB1 was used to infect four additional clinical isolates of A. baumannii, one clinical isolate of Stenotrophomonas maltophilia, and Pseudomonas aeruginosa lab strains PAK and PAO1, none of the tested strains was found susceptible, indicating a relatively narrow host range for phage AB1.

Conclusion

Phage AB1 was capable of eliciting efficient lysis of A. baumannii, revealing its potential as a non-toxic sanitizer for controlling A. baumannii infection and contamination in both hospital and other public environments.

Structure of eight streptococcal bacteriophages

Eight phages from groups A, B, C, E, G, and H streptococci were propagated in their own hosts, purified, and examined for morphology; the size, shape, and structure of their extracted nucleic acids was also examined. Electron microscopy showed three types of phage morphology. All eight phages possess linear double-stranded DNAs of molecular weights ranging from 10.5 X 10(6) to 24 X 10(6). Four phages from three different serological groups presented an identical pattern of restriction enzyme fragments. As shown by BAL31 digestion prior to restriction and by reanneling experiments, all but one DNA is circularly permuted. Terminal repetition is also present in six phage DNAs.

Protease-sensitive transfection of Streptococcus pneumoniae with bacteriophage Cp-1 DNA

The transfecting activity of pneumococcal phage Cp-1 DNA was destroyed by treatment with proteolytic enzymes, although these enzymes did not affect transfection with bacteriophage Dp-4 DNA. This transfection was stimulated by calcium ions. Protease-treated Cp-1 DNA competes for binding and uptake with transforming pneumococcal DNA as well as with transfecting Dp-4 DNA to approximately the same extent as does untreated Cp-1 DNA. In addition, [3H]thymidine-labeled Cp-1 DNA, treated with proteases or untreated, was absorbed with the same efficiency. These data suggest that uptake of Cp-1 DNA is not affected by protease treatment. [3H]thymidine-labeled Cp-1 DNA showed remarkable resistance against surface nuclease activity of competent wild-type cells. The monomeric form of the Cp-1 DNA-protein complex showed a linear dose response in transfection.

Purification and immunochemical characterization of Streptococcus sanguis serotype I carbohydrate antigen

The serotype-specific antigen of Streptococcus sanguis ST3 (serotype I, biotype A) was extracted, chromatographically purified, and characterized by immunological and chemical methods. The antigen was extracted from purified cell walls with hot trichloroacetic acid, followed by ion-exchange chromatography on a DEAE-Sephadex A-25 column and gel filtration through a Sephadex G-100 column. A peak fraction was obtained that gave a single precipitin band when reacted with anti-type I serum. The type I antigen was a polysaccharide composed of glucose, rhamnose, and N-acetylglucosamine in a molar ratio of 1.4:2.5:1.0. Quantitative precipitin inhibition tests with various haptenic sugars indicated that an alpha-glucosidic linkage is the immunodeterminant of the type I antigen.

Isolation and characterization of a new bacteriophage, Cp-1, infecting Streptococcus pneumoniae

Several pneumococcal phages showing a morphology completely different from those of all other previously found pneumococcal bacteriophages have been isolated. Bacteriophage Cp-1, one of the phages isolated, showed an irregular hexagonal structure and a short tail of 20 nm. The virion density was 1.46 g/cm3. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of nine polypeptides. The polypeptide showing a molecular weight of 39,000 accounted for more than the 90% of the total protein. The nucleic acid of Cp-1 was linear, double-stranded DNA with a mean length of 6.3 microns and a guanine-plus-cytosine content of 41%; its buoyant density was 1.699 and 1.422 g/cm3 in CsCl and CS2SO4, respectively. Its sedimentation coefficient (S20,w) was 19S. Cp-1 DNA showed a remarkable resistance to a large number of restriction endonucleases. A total of 12 fragments, ranging in molecular weight from 1.3 X 10(6) to 0.09 X 10(6), were produced by AluI, two fragments (molecular weight, 5.5 X 10(6) and 0.9 X 10(6)) were generated by HindIII, and two fragments (molecular weight, 6.0 X 10(6) and 5.7 X 10(6)) were produced by HaeIII. The easy visualization of th plaques produced by Cp-1, the small size of Cp-1 DNA (12 X 10(6) daltons), and other biological and physiochemical properties make this phage potentially useful for genetic studies.

Spiroplasmavirus citri 3: propagation, purification, proteins, and nucleic acid

SVC3 is a short-tailed polyhedral virus particle morphologically detectable in many spiroplasmas. It was isolated from two different spiroplasmas (Spiroplasma citri and the suckling mouse cataract agent) by infecting lawns and broth culture of another strain of Spiroplasmavirus citri. Virions from either donor strain had a buoyant density of 1.26 grams per cubic centimeter (metrizamide) or 1.45 grams per cubic centimeter (cesium chloride), and contained five proteins and linear double-stranded DNA with a molecular weight of 14 X 10(6). Other spiroplasmaviruses have not been propagated, and the molecular weights of double-stranded DNA from other mycoplasma (Acholeplasma) viruses are unknown.