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

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 beta-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

Characterization of the newly isolated lytic bacteriophages KTN6 and KT28 and their efficacy against Pseudomonas aeruginosa biofilm

We here describe two novel lytic phages, KT28 and KTN6, infecting Pseudomonas aeruginosa, isolated from a sewage sample from an irrigated field near Wroclaw, in Poland. Both viruses show characteristic features of Pbunalikevirus genus within the Myoviridae family with respect to shape and size of head/tail, as well as LPS host receptor recognition. Genome analysis confirmed the similarity to other PB1-related phages, ranging between 48 and 96%. Pseudomonas phage KT28 has a genome size of 66,381 bp and KTN6 of 65,994 bp. The latent period, burst size, stability and host range was determined for both viruses under standard laboratory conditions. Biofilm eradication efficacy was tested on peg-lid plate assay and PET membrane surface. Significant reduction of colony forming units was observed (70-90%) in 24 h to 72 h old Pseudomonas aeruginosa PAO1 biofilm cultures for both phages. Furthermore, a pyocyanin and pyoverdin reduction tests reveal that tested phages lowers the amount of both secreted dyes in 48-72 h old biofilms. Diffusion and goniometry experiments revealed the increase of diffusion rate through the biofilm matrix after phage application. These characteristics indicate these phages could be used to prevent Pseudomonas aeruginosa infections and biofilm formation. It was also shown, that PB1-related phage treatment of biofilm caused the emergence of stable phage-resistant mutants growing as small colony variants

Flax Fiber Hydrophobic Extract Inhibits Human Skin Cells Inflammation and Causes Remodeling of Extracellular Matrix and Wound Closure Activation

Inflammation is the basis of many diseases, with chronic wounds amongst them, limiting cell proliferation and tissue regeneration. Our previous preclinical study of flax fiber applied as a wound dressing and analysis of its components impact on the fibroblast transcriptome suggested flax fiber hydrophobic extract use as an anti-inflammatory and wound healing preparation. The extract contains cannabidiol (CBD), phytosterols, and unsaturated fatty acids, showing great promise in wound healing. In in vitro proliferation and wound closure tests the extract activated cell migration and proliferation. The activity of matrix metalloproteinases in skin cells was increased, suggesting activation of extracellular components remodeling. The expression of cytokines was diminished by the extract in a cannabidiol-dependent manner, but β-sitosterol can act synergistically with CBD in inflammation inhibition. Extracellular matrix related genes were also analyzed, considering their importance in further stages of wound healing. The extract activated skin cell matrix remodeling, but the changes were only partially cannabidiol- and β-sitosterol-dependent. The possible role of fatty acids also present in the extract is suggested. The study shows the hydrophobic flax fiber components as wound healing activators, with anti-inflammatory cannabidiol acting in synergy with sterols, and migration and proliferation promoting agents, some of which still require experimental identification

A suggested new bacteriophage genus, 'Kp34likevirus', within the Autographivirinae subfamily of Podoviridae

Klebsiella pneumoniae phages vB_KpnP_SU503 (SU503) and vB_KpnP_SU552A (SU552A) are virulent viruses belonging to the Autographivirinae subfamily of Podoviridae that infect and kill multi-resistant K. pneumoniae isolates. Phages SU503 and SU552A show high pairwise nucleotide identity to Klebsiella phages KP34 (NC_013649), F19 (NC_023567) and NTUH-K2044-K1-1 (NC_025418). Bioinformatic analysis of these phage genomes show high conservation of gene arrangement and gene content, conserved catalytically active residues of their RNA polymerase, a common and specific lysis cassette, and form a joint cluster in phylogenetic analysis of their conserved genes. Also, we have performed biological characterization of the burst size, latent period, host specificity (together with KP34 and NTUH-K2044-K1-1), morphology, and structural genes as well as sensitivity testing to various conditions. Based on the analyses of these phages, the creation of a new phage genus is suggested within the Autographivirinae, called "Kp34likevirus" after their type phage, KP34. This genus should encompass the recently genome sequenced Klebsiella phages KP34, SU503, SU552A, F19 and NTUH-K2044-K1-1

A Suggested New Bacteriophage Genus, "Kp34likevirus", within the Autographivirinae Subfamily of Podoviridae

Abstract: Klebsiella pneumoniae phages vB_KpnP_SU503 (SU503) and vB_KpnP_SU552A (SU552A) are virulent viruses belonging to the Autographivirinae subfamily of Podoviridae that infect and kill multi-resistant K. pneumoniae isolates. Phages SU503 and SU552A show high pairwise nucleotide identity to Klebsiella phages KP34 (NC_013649), F19 (NC_023567) and NTUH-K2044-K1-1 (NC_025418). Bioinformatic analysis of these phage genomes show high conservation of gene arrangement and gene content, conserved catalytically active residues of their RNA polymerase, a common and specific lysis cassette, and form a joint cluster in phylogenetic analysis of their conserved genes. Also, we have performed biological characterization of the burst size, latent period, host specificity (together with OPEN ACCESS Viruses 2015, 7 1805 KP34 and NTUH-K2044-K1-1), morphology, and structural genes as well as sensitivity testing to various conditions. Based on the analyses of these phages, the creation of a new phage genus is suggested within the Autographivirinae, called "Kp34likevirus" after their type phage, KP34. This genus should encompass the recently genome sequenced Klebsiella phages KP34, SU503, SU552A, F19 and NTUH-K2044-K1-1