A bacteriophage-induced depolymerase active on Klebsiella K11 capsular polysaccharide

Directed Evolution of Replication-Competent Double-Stranded DNA Bacteriophage toward New Host Specificity

In the fight against antimicrobial resistance, bacteriophages are a promising alternative to antibiotics. However, due to their narrow spectra, phage therapy requires the careful matching between the host and bacteriophage to be effective. Despite our best efforts, nature remains as the only source of novel phage specificity. Directed evolution can potentially open an avenue for engineering phage specificity and improving qualities of phages that are not strongly selected for in their natural environments but are important for therapeutic applications. In this work, we present a strategy that generates large libraries of replication-competent phage variants directly from synthetic DNA fragments, with no restriction on their host specificity. Using the T7 bacteriophage as a proof-of-concept, we created a large library of tail fiber mutants with at least 10⁷ unique variants. From this library, we identified mutants that have broadened specificity as evidenced by their novel lytic activity against Yersinia enterocolitica, a strain that the wild-type T7 was unable to lyse. Using the same concept, mutants with improved lytic efficiency and characteristics, such as lytic condition tolerance and resistance suppression, were also identified. However, the observed limitations in altering host specificity by tail fiber mutagenesis suggest that other bottlenecks could be of equal or even greater importance.

Bacteriophage SRD2021 Recognizing Capsular Polysaccharide Shows Therapeutic Potential in Serotype K47 Klebsiella pneumoniae Infections

Klebsiella pneumoniae is an opportunistic pathogen posing an urgent threat to global public health, and the capsule is necessary for K. pneumoniae infection and virulence. Phage-derived capsule depolymerases have shown great potential as antivirulence agents in treating carbapenem-resistant K. pneumoniae (CRKP) infections. However, the therapeutic potential of phages encoding depolymerases against CRKP remains poorly understood. In this study, we identified a long-tailed phage SRD2021 specific for mucoid CRKP with capsular K47 serotype, which is the predominant infectious K-type in Asia. Genome sequencing revealed that ΦSRD2021 belonged to the Drulisvirus genus and exhibited a capsular depolymerase domain in its tail fiber protein. A transposon-insertion library of host bacteria was constructed to identify the receptor for ΦSRD2021. We found that most phage-resistant mutants converted to a nonmucoid phenotype, including the mutant in wza gene essential for capsular polysaccharides export. Further knockout and complementation experiments confirmed that the Δwza mutant avoided adsorption by ΦSRD2021, indicating that the K47 capsular polysaccharide is the necessary receptor for phage infection. ΦSRD2021 lysed the bacteria mature biofilms and showed a therapeutic effect on the prevention and treatment of CRKP infection in the Galleria mellonella model. Furthermore, ΦSRD2021 also reduced the colonized CRKP in mouse intestines significantly. By recognizing the host capsule as a receptor, our results showed that ΦSRD2021 may be used as a potential antibacterial agent for K47 serotype K. pneumoniae infections.

Engineering the Modular Receptor-Binding Proteins of Klebsiella Phages Switches Their Capsule Serotype Specificity

The high specificity of bacteriophages is driven by their receptor-binding proteins (RBPs). Many Klebsiella bacteriophages target the capsular exopolysaccharide as the receptor and encode RBPs with depolymerase activity. The modular structure of these RBPs with an N-terminal structural module to attach the RBP to the phage tail, and a C-terminal specificity module for exopolysaccharide degradation, supports horizontal transfer as a major evolutionary driver for Klebsiella phage RBPs. We mimicked this natural evolutionary process by the construction of modular RBP chimeras, exchanging N-terminal structural modules and C-terminal specificity modules. All chimeras strictly follow the capsular serotype specificity of the C-terminal module. Transplanting chimeras with a K11 N-terminal structural RBP module in a Klebsiella phage K11 scaffold results in a capsular serotype switch and corresponding host range modification of the synthetic phages, demonstrating that horizontal transfer of C-terminal specificity modules offers Klebsiella phages an evolutionary highway for rapid adaptation to new capsular serotypes.

Modular prophage interactions driven by capsule serotype select for capsule loss under phage predation

Klebsiella species are able to colonize a wide range of environments and include worrisome nosocomial pathogens. Here, we sought to determine the abundance and infectivity of prophages of Klebsiella to understand how the interactions between induced prophages and bacteria affect population dynamics and evolution. We identified many prophages in the species, placing these taxa among the top 5% of the most polylysogenic bacteria. We selected 35 representative strains of the Klebsiella pneumoniae species complex to establish a network of induced phage-bacteria interactions. This revealed that many prophages are able to enter the lytic cycle, and subsequently kill or lysogenize closely related Klebsiella strains. Although 60% of the tested strains could produce phages that infect at least one other strain, the interaction network of all pairwise cross-infections is very sparse and mostly organized in modules corresponding to the strains' capsule serotypes. Accordingly, capsule mutants remain uninfected showing that the capsule is a key factor for successful infections. Surprisingly, experiments in which bacteria are predated by their own prophages result in accelerated loss of the capsule. Our results show that phage infectiousness defines interaction modules between small subsets of phages and bacteria in function of capsule serotype. This limits the role of prophages as competitive weapons because they can infect very few strains of the species complex. This should also restrict phage-driven gene flow across the species. Finally, the accelerated loss of the capsule in bacteria being predated by their own phages, suggests that phages drive serotype switch in nature.

[Creation of synthetic bacterial viruses]

Bacteria are closely related with human health and diseases. For example, the emergence of drug-resistant bacteria is a serious problem in the world. Studying the human microbiome shows its important role for our health. But we have very limited tools to edit bacterial population. Antibiotics are generally broad-spectrum and unable to kill only bad bacteria. The natural enemies of bacteria, called bacteriophage (phage), have highly specific host range, and thus promising candidates for targeted bacterial population editing. However, isolation and characterization of natural phages can be a time-, labor- and cost-intensive way. Also, developing phage-based therapeutics and diagnostics is limited by the difficulty of engineering phages. Here, I describe a phage genome-engineering platform and synthetic phages with tunable host ranges to overcome these challenges.

Phage-Borne Depolymerases Decrease Klebsiella pneumoniae Resistance to Innate Defense Mechanisms

Klebsiella pneumoniae produces capsular polysaccharides that are a crucial virulence factor protecting bacteria against innate response mechanisms of the infected host. Simultaneously, those capsules are targeted by specific bacteriophages equipped with virion-associated depolymerases able to recognize and degrade these polysaccharides. We show that Klebsiella phage KP32 produces two capsule depolymerases, KP32gp37 and KP32gp38, with a high specificity for the capsular serotypes K3 and K21, respectively. Together, they determine the host spectrum of bacteriophage KP32, which is limited to strains with serotype K3 and K21. Both depolymerases form a trimeric β-structure, display moderate thermostability and function optimally under neutral to alkaline conditions. We show that both depolymerases strongly affect the virulence of K. pneumoniae with the corresponding K3 and K21 capsular serotypes. Capsule degradation renders the otherwise serum-resistant cells more prone to complement-mediated killing with up to four log reduction in serum upon exposure to KP32gp37. Decapsulated strains are also sensitized for phagocytosis with a twofold increased uptake. In addition, the intracellular survival of phagocytized cells in macrophages was significantly reduced when bacteria were previously exposed to the capsule depolymerases. Finally, depolymerase application considerably increases the lifespan of Galleria mellonella larvae infected with K. pneumoniae in a time- and strain-dependent manner. In sum, capsule depolymerases are promising antivirulence compounds that act by defeating a major resistance mechanism of K. pneumoniae against the innate immunity.

Bacteriophage-encoded virion-associated enzymes to overcome the carbohydrate barriers during the infection process

Bacteriophages are bacterial viruses that infect the host after successful receptor recognition and adsorption to the cell surface. The irreversible adherence followed by genome material ejection into host cell cytoplasm must be preceded by the passage of diverse carbohydrate barriers such as capsule polysaccharides (CPSs), O-polysaccharide chains of lipopolysaccharide (LPS) molecules, extracellular polysaccharides (EPSs) forming biofilm matrix, and peptidoglycan (PG) layers. For that purpose, bacteriophages are equipped with various virion-associated carbohydrate active enzymes, termed polysaccharide depolymerases and lysins, that recognize, bind, and degrade the polysaccharide compounds. We discuss the existing diversity in structural locations, variable architectures, enzymatic specificities, and evolutionary aspects of polysaccharide depolymerases and virion-associated lysins (VALs) and illustrate how these aspects can correlate with the host spectrum. In addition, we present methods that can be used for activity determination and the application potential of these enzymes as antibacterials, antivirulence agents, and diagnostic tools.

Capsule-Targeting Depolymerase, Derived from Klebsiella KP36 Phage, as a Tool for the Development of Anti-Virulent Strategy

The rise of antibiotic-resistant Klebsiella pneumoniae, a leading nosocomial pathogen, prompts the need for alternative therapies. We have identified and characterized a novel depolymerase enzyme encoded by Klebsiella phage KP36 (depoKP36), from the Siphoviridae family. To gain insights into the catalytic and structural features of depoKP36, we have recombinantly produced this protein of 93.4 kDa and showed that it is able to hydrolyze a crude exopolysaccharide of a K. pneumoniae host. Using in vitro and in vivo assays, we found that depoKP36 was also effective against a native capsule of clinical K. pneumoniae strains, representing the K63 type, and significantly inhibited Klebsiella-induced mortality of Galleria mellonella larvae in a time-dependent manner. DepoKP36 did not affect the antibiotic susceptibility of Klebsiella strains. The activity of this enzyme was retained in a broad range of pH values (4.0–7.0) and temperatures (up to 45 °C). Consistently, the circular dichroism (CD) spectroscopy revealed a highly stability with melting transition temperature (Tm) = 65 °C. In contrast to other phage tailspike proteins, this enzyme was susceptible to sodium dodecyl sulfate (SDS) denaturation and proteolytic cleavage. The structural studies in solution showed a trimeric arrangement with a high β-sheet content. Our findings identify depoKP36 as a suitable candidate for the development of new treatments for K. pneumoniae infections.

Engineering Modular Viral Scaffolds for Targeted Bacterial Population Editing

Bacteria are central to human health and disease, but existing tools to edit microbial consortia are limited. For example, broad-spectrum antibiotics are unable to accurately manipulate bacterial communities. Bacteriophages can provide highly specific targeting of bacteria, but assembling well-defined phage cocktails solely with natural phages can be a time-, labor- and cost-intensive process. Here, we present a synthetic-biology strategy to modulate phage host ranges by engineering phage genomes in Saccharomyces cerevisiae. We used this technology to redirect Escherichia coli phage scaffolds to target pathogenic Yersinia and Klebsiella bacteria, and conversely, Klebsiella phage scaffolds to target E. coli by modular swapping of phage tail components. The synthetic phages achieved efficient killing of their new target bacteria and were used to selectively remove bacteria from multi-species bacterial communities with cocktails based on common viral scaffolds. We envision that this approach will accelerate phage-biology studies and enable new technologies for bacterial population editing.

Thermal treatment of the bacteriophage lysate of Klebsiella pneumoniae B5055 as a step for the purification of capsular depolymerase enzyme

The lytic bacteriophage which produces the hydrolase enzyme capable of depolymerizing exopolysaccharide of Klebsiella pneumoniae and of other bacteria was isolated earlier. In this study, a simple method of depolymerase purification from the phage lysate by dissociating the enzyme from the phage particle was developed. The bacteriophage showed a relatively smaller plaque size surrounded by a wide halo indicating a depolymerase action on the capsular polysaccharide of K. pneumoniae B5055. The depolymerase activity was associated predominantly with the phage particles. Different methods have been used by various researchers to dissociate the enzyme associated with phage particles either by exposure to chemicals or by altering the environmental conditions. In this study, the potential application of thermal treatment of the bacteriophage lysate was evaluated as a step for the purification of depolymerase in comparison to the mild acid treatment method of Rieger et al. (1975). The results showed that the relative thermal stability of phage depolymerase at 60°C for 30min was the basis for harvesting the enzyme leading to disintegration of all phage particles in the lysate. Both thermal and mild acid treatment resulted in comparable enzyme levels, however; mild acid treatment appeared to be cumbersome and cause chemical contamination.

Genome organization and characterization of mycobacteriophage Bxb1

Mycobacteriophage Bxb1 is a temperate phage of Mycobacterium smegmatis. The morphology of Bxb1 particles is similar to that of mycobacteriophages L5 and D29, although Bxb1 differs from these phages in other respects. First, it is heteroimmune with L5 and efficiently forms plaques on an L5 lysogen. Secondly, it has a different host range and fails to infect slow-growing mycobacteria, using a receptor system that is apparently different from that of L5 and D29. Thirdly, it is the first mycobacteriophage to be described that forms a large prominent halo around plaques on a lawn of M. smegmatis. The sequence of the Bxb1 genome shows that it possesses a similar overall organization to the genomes of L5 and D29 and shares weak but detectable DNA sequence similarity to these phages within the structural genes. However, Bxb1 uses a different system of integration and excision, a repressor with different specificity to that of L5 and encodes a large number of novel gene products including several with enzymatic functions that could degrade or modify the mycobacterial cell wall.

Sequence of a conditionally essential region of bacteriophage T3, including the primary origin of DNA replication

The 3526 base-pair nucleotide sequence from near the end of bacteriophage T3 gene 1 to within the coding sequence of gene 2.5 is given. It includes the complete coding sequences for nine known or presumptive proteins, most of which are only conditionally essential for phage growth. The sequence includes five promoters for the phage RNA polymerase, the terminator for early (host enzyme-catalyzed) transcription, and two recognition sites for RNAase III. The primary origin of T3 DNA replication that is utilized by the phage in vivo has been localized to a 142 base-pair region. It has several features in common with the phage T7 origin of DNA replication, and exhibits considerable homology to recognition sites for the mRNA processing enzyme RNAase III. It is proposed that the primary origin of T3 DNA replication may have evolved directly from an RNAase III recognition site. The deletions present in a number of T3 mutant strains and the location of the nucleotide changes in several T3 strains that are defective in their ability to grow on F+-containing strains or on optA mutant hosts have been determined. We discuss how T3 may have become genetically isolated from its relatives in the T7-T3 group and simultaneously acquired novel biological and biochemical properties.

Purification and properties of an endo-alpha-mannan hydrolase from the mushroom Volvariella volvacea

The enzyme, endo-alpha-mannanase, from culture filtrate of a mushroom Volvariella volvacea has been purified 73-fold by acetone precipitation, ion-exchange chromatography (DEAE-Sephadex), and gel-permeation chromatographies on Bio-Gel P-300 and on Sephacryl S-200 columns. The enzyme preparation gave a single protein band on sodium dodecyl sulfate-disc gel electrophoresis at pH 6.8 and has a molecular weight of approx. 56,000. It has no alpha- or beta-mannosidase activity and does not act on beta-gluco-or galactomannan. The enzyme shows maximum activity on baker's yeast alpha-mannan at pH 5.0 and at 55 degrees C, and is fairly stable between pH 3 and 6 and temperatures up to 50 degrees C. The Km is 32.25 mg mannan/ml. Enzyme activity is inhibited by Hg2+, sodium azide, iodoacetic acid, EDTA, and Ag+, in decreasing order.

Substrate specificity of two bacteriophage-associated endo-N-acetylneuraminidases

For Escherichia coli Bos12 (O16:K92:H-), a bacteriophage (phi 92) has been isolated which carries a depolymerase active on the K92 capsular polysaccharide. As seen under the electron microscope, phi 92 belongs to Bradley's morphology group A and is different from the phage phi 1.2 previously described (Kwiatkowski et al., J. Virol. 43:697-704, 1982), which grows on E. coli K235 (O1:K1:H-), depolymerizes colominic acid, and belongs to morphology group C. The specificity of the phi 1.2- and phi 92-associated endo-N-acetylneuraminidases has been studied with respect to the following substrates (all alkali treated, and where NeuNAc represents N-acetylneuraminic acid): (i) [-alpha-NeuNAc-(2 leads to 8)-]n (colominic acid), (ii) [-alpha-NeuNAc-(2 leads to 8)-alpha-NeuNAc-(2 leads to 9)-]n (E. coli K92 polysaccharide), and (iii) [-alpha-NeuNAc-(2 leads to 9)-]n (Neisseria meningitidis type C capsular polysaccharide). The increase in periodate consumption of these glycans upon incubation with purified phi 1.2 or phi 92 particles was measured, and the split products obtained from all substrates after exhaustive degradation were analyzed by gel chromatography. It was found that the Neisseria polysaccharide is not appreciably affected by either virus enzyme and that phi 1.2 only depolymerizes a small fraction of the K92 glycan. Colominic acid, however, is completely degraded by both agents, phi 92 yielding smaller fragments (one to six NeuNAc residues) than phi 1.2 (two to seven). Phage phi 92 additionally depolymerizes the K92 glycan, essentially to oligosaccharides of two, four, and six residues. The size distribution of these K92 oligosaccharides indicates that the phi 92 enzyme predominantly cleaves the alpha(2 leads to 8) linkages in this polymer.

Endo-N-acetylneuraminidase associated with bacteriophage particles

A bacteriophage (phi 1.2) has been isolated for Escherichia coli K235 (O1:K1:H-). phi 1.2 is specific for the host capsular polysaccharide (colominic acid). The phage forms plaques with acapsular halos and thus carries a glycanase activity for colominic acid, a homopolymer of alpha (2 leads to 8)-linked N-acetylneuraminic acid (NeuNAc) residues. Upon incubation with purified phi 1.2 particles, a solution of K1 polysaccharide loses viscosity and consumes increasing amounts of periodate. Also, by gel filtration, the production of colominic oligosaccharides (down to a size of two to three NeuNAc residues) can be demonstrated. No NeuNAc monomers, however, are formed. The capsules of E. coli strains with the K92 antigen, which consists of NeuNAc residues linked by alternating alpha (2 leads to 8) and alpha (2 leads to 9) bonds, are also depolymerized by the phi 1.2 enzyme. Under the electron microscope, phage phi 1.2 is seen to belong to Bradley's morphology group C (D. E. Bradley, Bacteriol. Rev. 31:230-314, 1967); it has an isometric head, carrying a baseplate with six spikes. By analogy to other virus particles with host capsule depolymerase activity, it is probable that the phi 1.2 endo-N-acetylneuraminidase activity is associated with these spikes.

Substrate specificity of the glycanase activity associated with particles of Klebsiella bacteriophage no. 6

A glycanase activity associated with the particles of Klebsiella bacteriophage No. 6 catalyses cleavage of O-beta-D-glycopyranosyl-(1 leads to 3)-4,6-O-(1-carboxyethylidene)-beta-D-mannopyranose linkages in Klebsiella serotype-6 capsular polysaccharide. Of 74 heterologous Klebsiella polysaccharides and two derivatives of the type-6 glycan, only the type-1 and type-57 polymers were additionally degraded by the phage-6 enzyme. The repeating units in the three substrates have a 1ax leads to 3eq, 1eq leads to eq-linked chain D-gluco- or D-galacto-pyranosyl residue in common (which constitutes the reducing end after glycanase action), and a carboxyl group on the next hexopyranosyl residue. Of the 72 polysaccharides not affected by the viral enzyme, at least the type-11 and type-21 glycans also contain the same homology of primary structure. This indicates that the conformation at the glycanase recognition-site also constitutes an important feature of the substrates.

Klebsiella serotype-13 capsular polysaccharide: primary structure and depolymerization by a bacteriophage-borne glycanase

Periodate oxidation and Smith degradation, methylation analysis including uronic acid degradation, partial hydrolysis with acid, bacteriophage degradation, and p.m.r. spectroscopy have been used to elucidate the primary structure of the Klebsiella serotype-13 capsular polysaccharide. The polymer consists of pentasaccharide repeating-units comprising a 4)-beta-D-Manp-(1 leads to 4)-alpha-D-Glcp-(1 leads to 3)-beta-D-Glcp-(1 leads to chain with a 3,4-O-(1-carboxyethylidene)-beta-D-Galp-(1 leads to 4)-alpha-D-GlcAp-(1 leads to branch at position 3 of the mannose. It is shown that there is a glycanase activity associated with particles of Klebsiella bacteriophage No. 13, which catalyses hydrolysis of chain beta-D-Glcp-(1 leads to 4)-beta-D-Manp linkages in the type-13 polysaccharide. The chemical basis of some serological cross-reactions of the Klebsiella K13 antigen is discussed.

Polysaccharide capsule of Escherichia coli: microscope study of its size, structure, and sites of synthesis

This report describes the structure, size, and shape of the uncollapsed polysaccharide capsule of Escherichia coli strain Bi 161/42 [O9:K29(A):H-], its ultrastructural preservation as well as the filamentous components of the isolated capsular material. In a temperature-sensitive mutant, sites were localized at which capsular polysaccharide is "exported" to the cell surface. The highly hydrated capsule of the wild-type cells was visible in the uncollapsed state after freeze-etching, whereas dehydration in greater than or equal to 50% acetone or alcohol caused the capsule to collapse into thick bundles. This was prevented by pretreatment of the cell with capsule-specific immunoglobulin G; the capsule appeared as a homogeneous layer of 250- to 300-nm thickness. The structural preservation depended on the concentration of the anti-capsular immunoglobulin G. Temperature-sensitive mutants, unable to produce capsular antigen at elevated temperatures, showed, 10 to 15 min after shift down to permissive temperature, polysaccharide strands with K29 specificity appearing at the cell surface at roughly 20 sites per cell; concomitantly, capsule-directed antibody started to agglutinate the bacteria. The sites at which the new antigen emerged were found in random distribution over the entire surface of the organism. Spreading of purified polysaccharide was achieved on air-water interfaces; after subsequent shadow casting with heavy metal, filamentous elements were observed with a smallest class of filaments measuring 250 nm in length and 3 to 6 nm in width. At one end these fibers revealed a knoblike structure of about 10-nm diameter. The slimelike polysaccharides from mutants produced filamentous bundles of greater than 100-microns length, with antigenic and phage-receptor properties indistinguishable from those of the wild-type K29 capsule antigen.

Klebsiella serotype 25 capsular polysaccharide: primary structure and depolymerization by a bacteriophage-borne glycanase

By partial acid hydrolysis, methylation and gas-liquid chromatography-mass spectrometry of the methylated monomers (as the alditol acetates), mass spectrometry of trimethylsilylated disaccharide alditols, as well as proton magnetic resonance, the primary structure of the Klebsiella serotype 25 capsular polysaccharide was elucidated. A glycanase activity, associated with the particles of newly isolated Klebsiella bacteriophage no. 25, was shown to catalyze the hydrolysis of the glycan.

Streptococcal bacteriophage 12/12-borne hyaluronidase and its characterization as a lyase (EC 4.2.99.1) by means of streptococcal hyaluronic acid and purified bacteriophage suspensions

Hyaluronic acid was obtained from filtrates of heat-killed cultures of Streptococcus pyogenes group A, strain K56, by simple ethanol precipitation and treatment with an adsorbent. The hyaluronic acid is pure as judged from chemical and sedimentation analyses. Particles of streptococcal bacteriophage 12/12 were isolated from phage-lysed group A streptococci by polyethylene glycol precipitation and isopyenic centrifugation. Electron micrographs of negatively stained preparations showed a typical Bradley group B virus with a long, flexible, cross-striated tail and a knob- or star-like structure at the distal tip of the tail. The hyaluronic acid is depolymerized upon incubation with the phage 12/12 virions. After extensive digestion, a mixture of at least four oligosaccharides is formed, the two smallest of which are a tetra- and octasaccharide terminating in reducing N-acetyl-D-glucosamine. The tetrasaccharide shows an absorption maximum at 231.5 nm with a molar extinction coefficient epsilon = 4820 litres X mole-1 X cm-1, and it is therefore concluded that the bacteriophage-borne hyaluronidase catalyses a beta-elimination. Accordingly it is classified as a hyaluronate lyase (EC 4.2.99.1).

Enzymic and molecular properties of base-plate parts of bacteriophage P22

Using 14C-labeled Salmonella bacterial cells as the substrate, the enzymic and molecular properties of the base-plate parts of phage P22 were studied. The base-plate part consisted of a single protein species which cleaved extensively the O-antigen of Salmonella typhimurium, Salmonelly schottmuellerie and with somewhat slower rate that of Salmonella typhi, releasing oligo-saccharide products with rhamnose at the reducing end. Much less cleavage was observed with a strain of S. typhimurium lysogenic for P22, and no significant reaction with Salmonella anatum, Salmonella newington and Salmonella minneapolis. The base-plate part enzyme was a very heat-stable protein and only 10-20% loss was observed after treatment at 85 degrees C for 5 min. The pH optimum of the enzyme was around 7.5, and the glycosidase activity was not influenced by the ionic strength (25-250 mM( of the medium or the presence of Mg2+. The molecular weight of the base-plate part was 320,000 by sedimentation equilibrium. Dodecylsulphate-acrylamide gel electrophoresis revealed a single band of molecular weight 77,000, indicating that a single base-plate part corresponds to a tetramer of identical subunits. Circular dichroism spectra of P22 base-plate parts showed a major contribution of beta structure. The protein was rich in acidic amino acids, glycine and serine.

Localization and functional role of the pseudomonas bacteriophage 2 depolymerase

The adsorption apparatus of phage 2 consits of a symmetrical base plate of snowflake appearance, composed of six droplike spikes 7.0 to 7.5 nm in length with a maximum diameter of 4.5 to 5.0 nm. The spikes are attached by their narrow ends to a central ring 7.0 to 7.5 nm in diameter. Phage 2 deopolymerase, a phage 2-induced hydrolytic enzyme, was found to be a structural protein of phage 2 or in close association with the base plate. Pdp1, a phage 2 mutant, possesses a polypeptide that is antigenically similar to the depolymerase, but devoid of hydrolytic activity. This polypeptide was found to be located in the region of the base plate of pdp1. Treatment of intact cells of strain BI with purified phage 2 depolymerase inhibited the adsorption of phage 2. When phage receptor-containing fractions of slime glycolipoprotein and lipopolysaccharide were hydrolyzed by the depolymerase, amino sugars were released, and the phage-inactivating activities of these fractions were lost. The depolymerase was also observed to induce the lysis of strain BI cells in hypotenic medium. The phage 2 depolymerase appears to play a role in adsorption and release of phage.

Escherichia coli capsule bacteriophages. VII. Bacteriophage 29-host capsular polysaccharide interactions

Different interactions between particles of Escherichia coli capsule bacteriophage 29 and its receptor, the E. coli serotype 29 capsular polysaccharide have been studied. The inactivation of phage 29 (8 x 10(3) PFU/ml) by isolated host capsular glycan was found to be physiologically insignificant (50% inactivation dose equals 100 mug after 1 h at 37 C). No adsorption (less than 2 x 10(4) PFU/mug) of the viruses to K29 polysaccharide-coated erythroyctes (at 0 or 37 C) was observed either. The phage particles were, however, found to catalyze the hydrolysis of beta-D-glucosido-(1leads to 3)-D-glucuronic acid bonds (arrow) in the receptor polymer, leading, ultimately, to the formation of a mixture of K29 hexasaccharide (one repeating unit), dodecasaccharide, and octadecasaccharide: (see article). Testing derivatives of K29 polysaccharide, as well as 82 heterologous bacterial (mainly Enteriobactericeae) capsular glycans, the viral glycanase was found to be highly specific; in accordance with the host range of phage 29, only one enzymatic cross-reaction (with the Klebsiella K31 polysaccharide) was observed. These and previous results, as well as the electron optical findings of M. E. Bayer and H. Thurow (submitted for publication), are discussed in terms of a unifying mechanism of phage 29-host capsule interaction. We propose that the viruses penetrate the capsules by means of their spike-associated glycanase activity, which leads them along capsular polysaccharide strands to membrane-cell wall adhesions where ejection of the viral genomes occurs.

The structure of Klebsiella serotype II capsular polysaccharide

Using periodate oxidation, methylation analysis, the characterization of oligosaccharides obtained by partial acid hydrolysis, p.m.r. spectroscopy, and analytical ultracentrifugation, the structure of the (mildly alkali-treated) Klebsiella serotype 11 capusular polysaccharide has been elucidated. The tetrasaccharide repeating-unit comprises the sequence yields 3)-beta-D-Glcp-(1 yields 3)-beta-D-GlcUAp-(1 yields 3)-alpha-D-Galp-(1 yields with a 4,6-O-(1-carboxyethylidene)-alpha-D-galactosyl residue linked to O-4 of the glucuronic acid residue. The structural basis for some serological cross-reactions of the Klebseilla K11 antigen is discussed, and it is shown that rabbit antisera against the Klebsiella K11 test-strain predominantly contain K agglutinins specific for branch-terminal 4,6-O-(1-carboxyethylidene)-D-galactose.

Bacteriophage-borne enzymes in carbohydrate chemistry. Part I. On the glycanase activity associated with particles of Klebsiella bacteriophage No. 11

The preparation and use of particles of Klebsiella bacteriophage No. 11 are described. A glycanase activity associated with the viruses catalyses the depolymerization of (alkali-treated) Klebsiella serotype 11 capsular polysaccharide, ultimately to a mixture of oligosaccharides consisting of one or two repeating units. Mainly glucosidic bonds are hydrolysed. The substrate specificity of the viral enzyme has been characterized by using derivatives of serotype-11 polysaccharide, as well as 81 heterologous, bacterial, capsular glycans. It is concluded that the glycanase will (at least) also depolymerize all polysaccharides containing the unsubstituted chain-trisaccharide repeating-unit of its natural substrate.

Escherichia coli capsule bacteriophages. III. Fragments of bacteriophage 29

A glycanase activity, catalyzing the depolymerization of host capsular polysaccharide, is associated with Escherichia coli capsule bacteriophage no. 29, a small virus with an isometric head, carrying a base plate with a set of spikes. The bacteriophage particles were disrupted by mild acid treatment (5 to 8 min at pH 3.5 and 37 C), and the enzymatically active fragments were isolated and subjected to sodium dodecyl sulfate-gel electrophoresis as well as to electron microscopy. Of the at least nine different polypeptide chains found in the complete virion, three (of 57,000 plus or minus 3,000, 29,500 plus or minus 2,000 and 13,500 plus or minus 1,000 daltons) were detected in detached base plates. They had the appearance of six-pointed stars of about 14 nm in outer diameter, with a central hole or prop, carrying six (or, possibly, a multiple thereof) spikes. Two sizes of polypeptide chains (57,000 and 29,500) were found in pure spikes, cylindrical particles of about 14.5 to 15 nm in length and 5 nm in diameter, and one (57,000) in -- still capsule depolymerizing -- spike subunits of roughly 5 nm in diameter. Phage 29 spike preparations, homogeneous in analytical ultracentrifugation and immunoelectrophoresis, were found to have a molecular weight of 245,000, as determined from the sedimentation equilibrium, and to contain equimolar amounts of the two polypeptides, probably three copies of each per organelle. The amino acid analysis of the isolated spikes revealed that aspartic acid, alanine, serine, and glycine are their dominant constituents; no amino sugars or other carbohydrates were detected in the preparations.

Escherichia coli capsule bacteriophages. V. Lysozyme 29

In addition to the spike-associated host capsule depolymerase, infection by Escherichia coli capsule bacteriophage no. 29 also induces the synthesis of a large bacteriolytic enzyme which has been purified to homogeneity. On incubation of isolated host murein sacculi with this enzyme, no amino groups but reducing sugar groups were liberated, and muraminitol, but no glucosaminitol, was found in the degraded sacculi after subsequent reduction with NaBH4. The bacteriolytic enzyme is thus another lysozyme (mucopeptide N-acetylmuramylhydrolase; EC 3.2.1.17). Electron optical visualization of negatively stained lysozyme specimens showed oblong particles of roughly 4.5 to 5.5 nm in diameter and 15 to 19 nm in length. Although the material tended to dissociate, a crude estimate of its molecular weight (270,000 plus or minus 30,000) could be obtained from these dimensions, from its sedimentation equilibrium, and from its behavior in gel chromatography. After disintegration of homogeneous lysozyme 29 by heating in solution with sodium dodecyl sulfate and dithiothreitol, polypeptides of one size only (about 46,000 dalton, probably six copies per molecule) were found in sodium dodecyl sulfate-polyacrylamide electrophoresis. The amino acid analysis of the enzyme accounted for more than 90% of its dry weight. One percent or less of the bacteriolytic activity in phage 29 lysates was found to be associated with the intact or disrupted virus particles, and a polypeptide of 46,000 daltons was not detected in the virions. These results strongly suggest that, in contrast to the host capsule depolymerase also induced by the same phage, and in spite of its comparatively large size, "lysozyme 29" does not constitute an integral part also of the homologous bacteriophage particles.

Escherichia coli capsule bacteriophages. IV. Free capsule depolymerase 29

The free host capsule depolymerase, induced by Escherichia coli capsule bacteriophage no. 29, and causing the formation of haloes around its plaques, has been purified to homogeneity. As judged from the following facts, this "enzyme" consists of free phage 29 spikes. (i) Detached phage organelles and depolymerase 29 particles exhibit the same molecular weight (about 245,000, as determined from the sedimentation equilibrium), contain polypeptide chains of the same two sizes (57,000 plus or minus 3,000 and 29,500 plus or minus 2,000, as determined by SDS-PAA gel electrophoresis), and have (within experimental error) the same sedimentation coefficient, isoelectric point, and amino acid composition. (ii) Isolated depolymerase and phage spikes in situ both catalyze the hydrolysis of glucosidic bonds in host capsular polysaccharide, leading ultimately to the formation of oligosaccharide fragments of one, two, and three hexasaccharide repeating units. (iii) Depolymerase 29 and phage 29 spikes have roughly the same electron optical dimensions. As tentatively estimated from the total and the virus-associated capsule depolymerase activity in the lysates, phage 29 infection seems to produce eight to seventeen times more free than incorporated spikes.