Double-stranded DNA Bacteriophages Research Articles

Physiochemical characterization of a potential Klebsiella phage MKP-1 and analysis of its application in reducing biofilm formation.

The common intestinal pathogen Klebsiella pneumoniae (K. pneumoniae) is one of the leading causes of fatal superbug infections that can resist the effects of commonly prescribed medicines. The uncontrolled use or misuse of antibiotics has increased the prevalence of drug-resistant K. pneumoniae strains in the environment. In the quest to search for alternative therapeutics for treating these drug-resistant infections, bacteriophages (bacterial viruses) emerged as potential candidates for in phage therapy against Klebsiella. The effective formulation of phage therapy against drug-resistant Klebsiella infections demands thorough characterization and screening of many bacteriophages. To contribute effectively to the formulation of successful phage therapy against superbug infections by K. pneumoniae, this study includes the isolation and characterization of a novel lytic bacteriophage MKP-1 to consider its potential to be used as therapeutics in treating drug-resistant Klebsiella infections. Morphologically, having a capsid attached to a long non-contractile tail, it was found to be a siphovirus that belongs to the class Caudoviricetes and showed infectivity against different strains of the target host bacterium. Comparatively, this double-stranded DNA phage has a large burst size and is quite stable in various physiological conditions. More interestingly, it has the potential to degrade the tough biofilms formed by K. pneumoniae (Klebsiella pneumoniae subsp. pneumoniae (Schroeter) Trevisan [ATCC 15380]) significantly. Thus, the following study would contribute effectively to considering phage MKP-1 as a potential candidate for phage therapy against Klebsiella infection.

Genomic and taxonomic evaluation of 38 Treponema prophage sequences

BackgroundDespite Spirochetales being a ubiquitous and medically important order of bacteria infecting both humans and animals, there is extremely limited information regarding their bacteriophages. Of the genus Treponema, there is just a single reported characterised prophage.ResultsWe applied a bioinformatic approach on 24 previously published Treponema genomes to identify and characterise putative treponemal prophages. Thirteen of the genomes did not contain any detectable prophage regions. The remaining eleven contained 38 prophage sequences, with between one and eight putative prophages in each bacterial genome. The prophage regions ranged from 12.4 to 75.1 kb, with between 27 and 171 protein coding sequences. Phylogenetic analysis revealed that 24 of the prophages formed three distinct sequence clusters, identifying putative myoviral and siphoviral morphology. ViPTree analysis demonstrated that the identified sequences were novel when compared to known double stranded DNA bacteriophage genomes.ConclusionsIn this study, we have started to address the knowledge gap on treponeme bacteriophages by characterising 38 prophage sequences in 24 treponeme genomes. Using bioinformatic approaches, we have been able to identify and compare the prophage-like elements with respect to other bacteriophages, their gene content, and their potential to be a functional and inducible bacteriophage, which in turn can help focus our attention on specific prophages to investigate further.

Isolation and characterization of a phage collection against Pseudomonas putida.

The environmental bacterium, Pseudomonas putida, possesses a broad spectrum of metabolic pathways. This makes it highly promising for use in biotechnological production as a cell factory, as well as in bioremediation strategies to degrade various aromatic pollutants. For P. putida to flourish in its environment, it must withstand the continuous threats posed by bacteriophages. Interestingly, until now, only a handful of phages have been isolated for the commonly used laboratory strain, P. putida KT2440, and no phage defence mechanisms have been characterized. In this study, we present a new Collection of Environmental P. putida Phages from Estonia, or CEPEST. This collection comprises 67 double-stranded DNA phages, which belong to 22 phage species and 9 phage genera. Our findings reveal that most phages in the CEPEST collection are more infectious at lower temperatures, have a narrow host range, and require an intact lipopolysaccharide for P. putida infection. Furthermore, we show that cryptic prophages present in the P. putida chromosome provide strong protection against the infection of many phages. However, the chromosomal toxin-antitoxin systems do not play a role in the phage defence of P. putida. This research provides valuable insights into the interactions between P. putida and bacteriophages, which could have significant implications for biotechnological and environmental applications.

Isolation, characterization and application of noble bacteriophages targeting potato common scab pathogen Streptomyces stelliscabiei

Bacteriophages have emerged as promising alternatives to pesticides for controlling bacterial pathogens in crops. Among these pathogens, Streptomyces stelliscabiei (syn. S. stelliscabiei) is a primary causative agent of potato common scab (PCS), resulting in substantial global economic losses. The traditional management methods for PCS face numerous challenges, highlighting the need for effective and environmentally friendly control strategies. In this study, we successfully isolated three novel bacteriophages, namely Psst1, Psst2, and Psst4, which exhibited a broad host range encompassing seven S. stelliscabiei strains. Morphological analysis revealed their distinct features, including an icosahedral head and a non-contractile tail. These phages demonstrated stability across a broad range of temperatures (20–50°C), pH (pH 3–11), and UV exposure time (80 min). Genome sequencing revealed double-stranded DNA phage with open reading frames encoding genes for phage structure, DNA packaging and replication, host lysis and other essential functions. These phages lacked genes for antibiotic resistance, virulence, and toxicity. Average nucleotide identity, phylogenetic, and comparative genomic analyses classified the three phages as members of the Rimavirus genus, with Psst1 and Psst2 representing novel species. All three phages efficiently lysed S. stelliscabiei in the liquid medium and alleviated scab symptom development and reduced pathogen abundance on potato slices. Furthermore, phage treatments of radish seedlings alleviated the growth inhibition caused by S. stelliscabiei with no disease symptoms. In soil potted experiments, phages significantly reduced disease incidence by 40%. This decrease is attributed to a reduction in pathogen density and the selection of S. stelliscabiei strains with reduced virulence and slower growth rates in natural environments. Our study is the first to report the isolation of three novel phages that infect S. stelliscabiei as a host bacterium. These phages exhibit a broad host range, and demonstrate stability under a variety of environmental conditions. Additionally, they demonstrate biocontrol efficacy against bacterial infections in potato slices, radish seedlings, and potted experiments, underscoring their significant potential as biocontrol agents for the effective management of PCS.

Characterization of a novel high-efficiency cracking Burkholderia gladiolus phage vB_BglM_WTB and its application in black fungus

Burkholderia gladiolus (B. gladiolus) is foodborne pathogenic bacteria producing bongkrekic acid (BA), which causes food poisoning and has a mortality rate of up to 40 % or more. However, no drugs have been reported in the literature for the prevention and treatment of this infection. In this study, a phage was identified to control B. gladiolus. The novel phage vB_BglM_WTB (WTB), which lyse B. gladiolus with high efficiency, was isolated from sewage of Huaihe Road Throttle Well Sewage Treatment Plant in Hefei. Transmission electron microscopy showed that WTB had an icosahedral head (69 ± 2 nm) and a long retractable tail (108 ± 2 nm). Its optimal temperature and pH ranges to control B. gladiolus were 25 °C -65 °C and 3–11 respectively. The phage WTB was identified as a linear double-stranded DNA phage of 68, 541 bp with 60.04 % G + C content, with a long latent period of 60 min. Phylogenetic analysis and comparative genetic analysis indicated that phage WTB has low identity (<50 %) with other phages, with the highest similarity to Burkholderia phage Maja (25.7 %), which showed that it does not belong to any previous genera recognized by the International Committee on Taxonomy of Viruses (ICTV) and was a candidate for a new genus within the Caudoviricetes. We have submitted a new proposal to ICTV to create a new genus, Bglawtbvirus. No transfer RNA (tRNA), virulence associated and antibiotic resistance genes were detected in phage WTB. Experimental results indicated that WTB at 4 °C and 25 °C had excellent inhibition activity against B. gladiolus in the black fungus, with an inhibition efficiency of over 99 %. The amount of B. gladiolus in the black fungus was reduced to a minimum of 89 CFU/mL when treated by WTB at 25 °C for 2 h. The inhibition rate remained at 99.97 % even after 12 h. The findings showed that the phage WTB could be applied as a food-cleaning agent for enhancing food safety and contributed to our understanding of phage biology and diversity.

Genomic characterization of SNW-1, a novel prophage of the deep-sea vent chemolithoautotroph Sulfurimonas indica NW79.

The globally widespread genus Sulfurimonas are playing important roles in different habitats, including the deep-sea hydrothermal vents. However, phages infecting Sulfurimonas have never been isolated and characterized to date. In the present study, a novel prophage SNW-1 was identified from Sulfurimonas indica NW79. Whole genome sequencing resulted in a circular, double-stranded DNA molecule of 37,096 bp with a mol% G+C content of 37. The genome includes 64 putative open reading frames, 33 of which code for proteins with predicted functions. Presence of hallmark genes associated with Caudoviricetes and genes involved in lysis and lysogeny indicated that SNW-1 should be a temperate, tailed phage. Phylogenetic and comparative proteomic analyses suggested that Sulfurimonas phage SNW-1 was distinct from other double stranded DNA phages and might represent a new viral genus.

Viral Genomic DNA Packaging Machinery.

Tailed double-stranded DNA bacteriophage employs a protein terminase motor to package their genome into a preformed protein shell-a system shared with eukaryotic dsDNA viruses such as herpesviruses. DNA packaging motor proteins represent excellent targets for antiviral therapy, with Letermovir, which binds Cytomegalovirus terminase, already licensed as an effective prophylaxis. In the realm of bacterial viruses, these DNA packaging motors comprise three protein constituents: the portal protein, small terminase and large terminase. The portal protein guards the passage of DNA into the preformed protein shell and acts as a protein interaction hub throughout viral assembly. Small terminase recognises the viral DNA and recruits large terminase, which in turn pumps DNA in an ATP-dependent manner. Large terminase also cleaves DNA at the termination of packaging. Multiple high-resolution structures of each component have been resolved for different phages, but it is only more recently that the field has moved towards cryo-EM reconstructions of protein complexes. In conjunction with highly informative single-particle studies of packaging kinetics, these structures have begun to inspire models for the packaging process and its place among other DNA machines.

Mitigation of biogenic methanethiol using bacteriophages in synthetic wastewater augmented with Pseudomonas putida

Wastewater malodour is the proverbial ‘elephant in the room’ notwithstanding its severe implications on sanitation, health, and hygiene. The predominant malodorous compounds associated with wastewater treatment plants and toilets are volatile organic compounds, such as hydrogen sulphide, ammonia, methanethiol, and organic acids. Among them, methanethiol warrants more attention owing to its relatively low olfactory threshold and associated cytotoxicity. This requires an efficient odour-abatement method since conventional techniques are either cost-prohibitive or leave recalcitrant byproducts. Bacteriophage-based methodology holds promise, and the described work explores the potential. In this study, a non-lysogenous Pseudomonas putida strain is used as a model organism that produces methanethiol in the presence of methionine. Two double-stranded DNA phages of genome sizes > 10 Kb were isolated from sewage. ɸPh_PP01 and ɸPh_PP02 were stable at suboptimal pH, temperature, and at 10% chloroform. Moreover, they showed adsorption efficiencies of 53% and 89% in 12 min and burst sizes of 507 ± 187 and 105 ± 7 virions per cell, respectively. In augmented synthetic wastewater, ɸPh_PP01 and ɸPh_PP02 reduced methanethiol production by 52% and 47%, respectively, with the concomitant reduction in P. putida by 3 logs in 6 h. On extension of the study in P. putida spiked-sewage sample, maximum reduction in methanethiol production was achieved in 3 h, with 49% and 48% for ɸPh_PP01 and ɸPh_PP02, respectively. But at 6 h, efficiency reduced to 36% with both the phages. The study clearly demonstrates the potential of phages as biocontrol agents in the reduction of malodour in wastewater.

Four additional natural 7-deazaguanine derivatives in phages and how to make them.

Bacteriophages and bacteria are engaged in a constant arms race, continually evolving new molecular tools to survive one another. To protect their genomic DNA from restriction enzymes, the most common bacterial defence systems, double-stranded DNA phages have evolved complex modifications that affect all four bases. This study focuses on modifications at position 7 of guanines. Eight derivatives of 7-deazaguanines were identified, including four previously unknown ones: 2'-deoxy-7-(methylamino)methyl-7-deazaguanine (mdPreQ1), 2'-deoxy-7-(formylamino)methyl-7-deazaguanine (fdPreQ1), 2'-deoxy-7-deazaguanine (dDG)and 2'-deoxy-7-carboxy-7-deazaguanine (dCDG). These modifications are inserted in DNA by a guanine transglycosylase named DpdA. Three subfamilies of DpdA had been previously characterized: bDpdA, DpdA1, and DpdA2. Two additional subfamilies were identified in this work: DpdA3, which allows for complete replacement of the guanines, and DpdA4, which is specific to archaeal viruses. Transglycosylases have now been identified in all phages and viruses carrying 7-deazaguanine modifications, indicating that the insertion of these modifications is a post-replication event. Three enzymes were predicted to be involved in the biosynthesis of these newly identified DNA modifications: 7-carboxy-7-deazaguanine decarboxylase (DpdL), dPreQ1 formyltransferase (DpdN)and dPreQ1 methyltransferase (DpdM), which was experimentally validated and harbors a unique fold not previously observed for nucleic acid methylases.

Four Novel Caudoviricetes Bacteriophages Isolated from Baltic Sea Water Infect Colonizers of Aurelia aurita.

The moon jellyfish Aurelia aurita is associated with a highly diverse microbiota changing with provenance, tissue, and life stage. While the crucial relevance of bacteria to host fitness is well known, bacteriophages have often been neglected. Here, we aimed to isolate virulent phages targeting bacteria that are part of the A. aurita-associated microbiota. Four phages (Pseudomonas phage BSwM KMM1, Citrobacter phages BSwM KMM2-BSwM KMM4) were isolated from the Baltic Sea water column and characterized. Phages KMM2/3/4 infected representatives of Citrobacter, Shigella, and Escherichia (Enterobacteriaceae), whereas KMM1 showed a remarkably broad host range, infecting Gram-negative Pseudomonas as well as Gram-positive Staphylococcus. All phages showed an up to 99% adsorption to host cells within 5 min, short latent periods (around 30 min), large burst sizes (mean of 128 pfu/cell), and high efficiency of plating (EOP > 0.5), demonstrating decent virulence, efficiency, and infectivity. Transmission electron microscopy and viral genome analysis revealed that all phages are novel species and belong to the class of Caudoviricetes harboring a tail and linear double-stranded DNA (formerly known as Siphovirus-like (KMM3) and Myovirus-like (KMM1/2/4) bacteriophages) with genome sizes between 50 and 138 kbp. In the future, these isolates will allow manipulation of the A. aurita-associated microbiota and provide new insights into phage impact on the multicellular host.

Isolation, characterization, therapeutic potency, and genomic analysis of a novel bacteriophage vB_KshKPC-M against carbapenemase-producing Klebsiella pneumoniae strains (CRKP) isolated from Ventilator-associated pneumoniae (VAP) infection of COVID-19 patients

BackgroundCarbapenem-resistant Klebsiella pneumoniae (CRKP) is a significant clinical problem, given the lack of therapeutic options. The CRKP strains have emerged as an essential worldwide healthcare issue during the last 10 years. Global expansion of the CRKP has made it a significant public health hazard. We must consider to novel therapeutic techniques. Bacteriophages are potent restorative cases against infections with multiple drug-resistant bacteria. The Phages offer promising prospects for the treatment of CRKP infections.ObjectiveIn this study, a novel K. pneumoniae phage vB_KshKPC-M was isolated, characterized, and sequenced, which was able to infect and lyse Carbapenem-resistant K. pneumoniae host specifically.MethodsOne hundred clinical isolates of K. pneumoniae were collected from patients with COVID-19 associated with ventilator-associated acute pneumonia hospitalized at Shahid Beheshti Hospital, Kashan, Iran, from 2020 to 2021. Initially, all samples were cultured, and bacterial isolates identified by conventional biochemical tests, and then the ureD gene was used by PCR to confirm the isolates. The Antibiotic susceptibility test in the disc diffusion method and Minimum inhibitory concentrations for Colistin was done and interpreted according to guidelines. Phenotypic and molecular methods determined the Carbapenem resistance of isolates. The blaKPC, blaNDM, and blaOXA-23 genes were amplified for this detection. Biofilm determination of CRKP isolates was performed using a quantitative microtiter plate (MTP) method. The phage was isolated from wastewater during the summer season at a specific position from Beheshti Hospital (Kashan, Iran). The sample was processed and purified against the bacterial host, a CRKP strain isolated from a patient suffering from COVID-19 pneumoniae and resistance to Colistin with high potency for biofilm production. This isolate is called Kp100. The separated phages were diluted and titration by the double overlay agar plaque assay. The separate Phage is concentrated with 10% PEG and stored at −80 °C until use. The phage host range was identified by the spot test method. The purified phage morphology was determined using a transmission electron microscope. The phage stability tests (pH and temperature) were analyzed. The effect of cationic ions on phage adsorption was evaluated. The optimal titer of bacteriophage was determined to reduce the concentration of the CRKP strain. One-step growth assays were performed to identify the purified phage burst’s latent cycle and size. The SDS-PAGE was used for phage proteins analysis. Phage DNA was extracted by chloroform technique, and the whole genome of lytic phage was sequenced using Illumina HiSeq technology (Illumina, San Diego, CA). For quality assurance and preprocessing, such as trimming, Geneious Prime 2021.2.2 and Spades 3.9.0. The whole genome sequence of the lytic phage is linked to the GenBank database accession number. RASTtk—v1.073 was used to predict and annotate the ORFs. Prediction of ORF was performed using PHASTER software. ResFinder is used to assess the presence of antimicrobial resistance and virulence genes in the genome. The tRNAs can-SE v2.0.6 is used to determine the presence of tRNA in the genome. Linear genome comparisons of phages and visualization of coding regions were performed using Easyfig 2.2.3 and Mauve 2.4.0. Phage lifestyles were predicted using the program PHACTS. Phylogenetic analysis and amino acid sequences of phage core proteins, such as the major capsid protein. Phylogenies were reconstructed using the Neighbor-Joining method with 1000 bootstrap repeat. HHpred software was used to predict depolymerase. In this study, GraphPad Prism version 9.1 was used for the statistical analysis. Student’s t-test was used to compare the sets and the control sets, and the significance level was set at P ≤ 0.05.ResultsPhage vB_KshKPC-M is assigned to the Siphoviridae, order Caudovirales. It was identified as a linear double-stranded DNA phage of 54,378 bp with 50.08% G + C content, had a relatively broad host range (97.7%), a short latency of 20 min, and a high burst size of 260 PFU/cell, and was maintained stable at different pH (3–11) and temperature (45–65 °C). The vB_KshKPC-M genome contains 91 open-reading frames. No tRNA, antibiotic resistance, toxin, virulence-related genes, or lysogen-forming gene clusters were detected in the phage genome.Comparative genomic analysis revealed that phage vB_KshKPC-M has sequence similarity to the Klebsiella phages, phage 13 (NC_049844.1), phage Sushi (NC_028774.1), phage vB_KpnD_PeteCarol (OL539448.1) and phage PWKp14 (MZ634345.1).ConclusionThe broad host range and antibacterial activity make it a promising candidate for future phage therapy applications. The isolated phage was able to lyse most of the antibiotic-resistant clinical isolates. Therefore, this phage can be used alone or as a phage mixture in future studies to control and inhibit respiratory infections caused by these bacteria, especially in treating respiratory infections caused by resistant strains in sick patients.

Isolation of new Klebsiella pneumoniae phage PSKP16.

Klebsiella pneumoniae is a clinically relevant opportunistic pathogen belonging to the Enterobacteriaceae family. It is in the top three bacteria associated with antimicrobial resistance deaths globally, and one of the most dangerous bacteria causing nosocomial infections. Phage therapy offers a potential option for the treatment of drug-resistant bacterial infections. Phage PSKP16 was isolated against K. pneumoniae, capsular type K2 (isolated from a wound infection). PSKP16 is a new lytic phage with a Siphovirus-like morphology. PSKP16 is a linear double stranded DNA phage with a GC content of 50% and genome size of 46,712 bp, for which we predicted 67 ORFs. PSKP16 belongs to the genus Webervirus and shows high evolutionary proximity to Klebsiella phages JY917, Sushi, and B1. Phage isolation is fast, cheap and efficient, but it requires time and characterization (which adds expense) to ensure that the isolated phages do not pose a health risk, which is essential to safely use phage therapy to treat life-threatening bacterial infections.

Loss of a Branch Sugar in the Acinetobacter baumannii K3-Type Capsular Polysaccharide Due To Frameshifts in the gtr6 Glycosyltransferase Gene Leads To Susceptibility To Phage APK37.1.

The type of capsular polysaccharide (CPS) on the cell surface of Acinetobacter baumannii can determine the specificity of lytic bacteriophage under consideration for therapeutic use. Here, we report the isolation of a phage on an extensively antibiotic resistant ST2 A. baumannii isolate AB5001 that carries the KL3 CPS biosynthesis gene cluster predicting a K3-type CPS. As the phage did not infect isolates carrying KL3 or KL22 and known to produce K3 CPS, the structure of the CPS isolated from A. baumannii AB5001 was determined. AB5001 produced a variant CPS form, K3-v1, that lacks the β-d-GlсpNAc side chain attached to the d-Galp residue in the K3 structure. Inspection of the KL3 sequence in the genomes of AB5001 and other phage-susceptible isolates with a KL3 locus revealed single-base deletions in gtr6, causing loss of the Gtr6 glycosyltransferase that adds the missing d-GlсpNAc side chain to the K3 CPS. Hence, the presence of this sugar profoundly restricts the ability of the phage to digest the CPS. The 41-kb linear double-stranded DNA (dsDNA) phage genome was identical to the genome of a phage isolated on a K37-producing isolate and thus was named APK37.1. APK37.1 also infected isolates carrying KL116. Consistent with this, K3-v1 resembles the K37 and K116 structures. APK37.1 is a Friunavirus belonging to the Autographiviridae family. The phage-encoded tail spike depolymerase DpoAPK37.1 was not closely related to Dpo encoded by other sequenced Friunaviruses, including APK37 and APK116. IMPORTANCE Lytic bacteriophage have potential for the treatment of otherwise untreatable extensively antibiotic-resistant bacteria. For Acinetobacter baumannii, most phage exhibit specificity for the type of capsular polysaccharide (CPS) produced on the cell surface. However, resistance can arise via mutations in CPS genes that abolish this phage receptor. Here, we show that single-base deletions in a CPS gene result in alteration of the final structure rather than deletion of the capsule layer and hence affect the ability of a newly reported podophage to infect strains producing the K3 CPS.

Characterization and genome analysis of Vibrio phage vB_VhaP_PG11, representing a new viral genus

Vibrio is a kind of common gram-negative bacteria, which is widely distributed in marine and estuarine environments. In the study, a novel marine phage vB_VhaP_PG11, infecting Vibrio hangzhouensis, was isolated from the offshore waters of Qingdao, China. vB_VhaP_PG11 is a double-stranded DNA phage. The whole genome proteomic tree shows that vB_VhaP_PG11 phage is related to two Vibrio phages, Vibrio phage 1.238.A._10N.261.52.F10 and Vibrio phage 1.245.O._10N.261.54.C7, but with low homology. Their amino acids identity with vB_VhaP_PG11 is 42.77 and 41.49% respectively. The prediction results of genome-blast distance phylogeny (GBDP) and the analysis gene-sharing network indicate that vB_VhaP_PG11 belongs to a new genus in Schitoviridae, named Qingschitovirus. The study of Vibrio phage vB_VhaP_PG11 provides basic information contributing to a better understanding of interactions between Vibrio phages and their hosts and helps analyze unknown viral sequences in the metagenomic database.

Antimicrobial properties of a multi-component alloy

High traffic touch surfaces such as doorknobs, countertops, and handrails can be transmission points for the spread of pathogens, emphasizing the need to develop materials that actively self-sanitize. Metals are frequently used for these surfaces due to their durability, but many metals also possess antimicrobial properties which function through a variety of mechanisms. This work investigates metallic alloys comprised of several metals which individually possess antimicrobial properties, with the target of achieving broad-spectrum, rapid sanitation through synergistic activity. An entropy-motivated stabilization paradigm is proposed to prepare scalable alloys of copper, silver, nickel and cobalt. Using combinatorial sputtering, thin-film alloys were prepared on 100 mm wafers with ≈50% compositional grading of each element across the wafer. The films were then annealed and investigated for alloy stability. Antimicrobial activity testing was performed on both the as-grown alloys and the annealed films using four microorganisms—Phi6, MS2, Bacillus subtilis and Escherichia coli—as surrogates for human viral and bacterial pathogens. Testing showed that after 30 s of contact with some of the test alloys, Phi6, an enveloped, single-stranded RNA bacteriophage that serves as a SARS-CoV-2 surrogate, was reduced up to 6.9 orders of magnitude (> 99.9999%). Additionally, the non-enveloped, double-stranded DNA bacteriophage MS2, and the Gram-negative E. coli and Gram-positive B. subtilis bacterial strains showed a 5.0, 6.4, and 5.7 log reduction in activity after 30, 20 and 10 min, respectively. Antimicrobial activity in the alloy samples showed a strong dependence on the composition, with the log reduction scaling directly with the Cu content. Concentration of Cu by phase separation after annealing improved activity in some of the samples. The results motivate a variety of themes which can be leveraged to design ideal antimicrobial surfaces.

Genome Sequence of a Lytic Staphylococcus aureus Bacteriophage Isolated from Breast Milk.

We identified a double-stranded DNA (dsDNA) bacteriophage appearing to belong to Herelleviridae, genus Kayvirus. The bacteriophage, Biyabeda-mokiny 1, was isolated from breast milk using a clinical isolate of Staphylococcus aureus. The genome is 141,091 bp in length and encodes 230 putative coding sequences.

Genome Sequences of Two Lytic Staphylococcus aureus Bacteriophages Isolated from Wastewater.

Two lytic double-stranded DNA (dsDNA) bacteriophages, belonging to the family Herelleviridae, were isolated from wastewater in Western Australia. Biyabeda-mokiny 2 appears to belong to the genus Kayvirus, and Koomba-kaat 1 to Silviavirus.

Metagenome-Assembled Genomes for "Candidatus Phormidium sp. Strain AB48" and Co-occurring Microorganisms from an Industrial Photobioreactor Environment.

Here, we report metagenome-assembled genomes for "Candidatus Phormidium sp. strain AB48" and three cooccurring microorganisms from a biofilm-forming industrial photobioreactor environment, using the PacBio sequencing platform. Several mobile genetic elements, including a double-stranded DNA phage and plasmids, were also recovered, with the potential to mediate gene transfer within the biofilm community.

Characterization of the newly isolated Pseudomonas phage vB_Pae_LC3I3

Here, we report the genome sequence of a double-stranded DNA siphovirus, vB_Pae_LC3I3 infective for P. aeruginosa PA14. Phage vB_Pae_LC3I3 was identified as a linear double-stranded DNA phage of 49,926 bp with 59% G+C content. The vB_Pae_LC3I3 genome contains 78 open reading frames, and the function of 22 ORFs can be predicted. Genome analysis confirmed the lysogenic nature of this phage, which encodes the typical lysogen-related integrase and CI/Cro regulator. One-step growth curve revealed that the latent period of phage vB_Pae_LC3I3 lasted for 30 min. And vB_Pae_LC3I3 showed good temperature stability and pH stability. Based on electron microscopy, phylogenetic, and comparative genomic analyses, this novel Pseudomonas temperate phage represents a novel unassigned siphoviruses cluster. The study of phage vB_Pae_LC3I3 will provide basic information for further research on treatment of P. aeruginosa infections.

Getting Outside the Cell: Versatile Holin Strategies Used by Distinct Phages to Leave Their Bacillus thuringiensis Host.

ABSTRACTHolins are small transmembrane proteins involved in the final stage of the lytic cycle of double-stranded DNA (dsDNA) phages. They cooperate with endolysins to achieve bacterial lysis, thereby releasing the phage progeny into the extracellular environment. Besides their role as membrane permeabilizers, allowing endolysin transfer and/or activation, holins also regulate the lysis timing. In this work, we provide functional characterization of the holins encoded by three phages targeting the Bacillus cereus group. The siphovirus Deep-Purple has a lysis cassette in which holP30 and holP33 encode two proteins displaying holin properties, including a transmembrane domain. The holin genes were expressed in Escherichia coli and induced bacterial lysis, with HolP30 being more toxic than HolP33. In Bacillus thuringiensis, the simultaneous expression of both holins was necessary to observe lysis, suggesting that they may interact to form functional pores. The myoviruses Deep-Blue and Vp4 both encode a single candidate holin (HolB and HolV, respectively) with two transmembrane domains, whose genes are not located near the endolysin genes. Their function as holin proteins was confirmed as their expression in E. coli impaired cell growth and viability. The HolV expression in B. thuringiensis also led to bacterial lysis, which was enhanced by coexpressing the holin with its cognate endolysin. Despite similar organizations and predicted topologies, truncated mutants of the HolB and HolV proteins showed different toxicity levels, suggesting that differences in amino acid composition influence their lysis properties.IMPORTANCE The phage life cycle ends with the host cell lysis, thereby releasing new virions into the environment for the next round of bacterial infection. Nowadays, there is renewed interest in phages as biocontrol agents, primarily due to their ability to cause bacterial death through lysis. While endolysins, which mediate peptidoglycan degradation, have been fairly well described, the pore-forming proteins, referred to as holins, have been extensively characterized in only a few model phages, mainly infecting Gram-negative bacteria. In this work, we characterized the holins encoded by a siphovirus and two myoviruses targeting members of the Gram-positive Bacillus cereus group, which comprises closely related species, including the well-known Bacillus anthracis, B. cereus sensu stricto, and Bacillus thuringiensis. Overall, this paper provides the first experimental characterization of holins encoded by B. cereus phages and reveals versatile lysis mechanisms used by these phages.