Isolation, characterization and complete genome sequence of PhaxI: a phage of Escherichia coli O157 : H7

Characterization and genome analysis of a broad host range lytic phage vB_SenS_TUMS_E19 against Salmonella enterica and its efficiency evaluation in the liquid egg

Salmonella enterica serovars are zoonotic bacterial that cause foodborne enteritis. Due to bacteria's antibiotic resistance, using bacteriophages for biocontrol and treatment is a new therapeutic approach. In this study, we isolated, characterized, and analyzed the genome of vB_SenS_TUMS_E19 (E19), a broad host range Salmonella bacteriophage, and evaluated the influence of E19 on liquid eggs infected with Salmonella enterica serovar Enteritidis. Transmission electron microscopy showed that the isolated bacteriophage had a siphovirus morphotype. E19 showed rapid adsorption (92% in 5 min), a short latent period (18 min), a large burst size (156 PFU per cell), and a broad host range against different Salmonella enterica serovars. Whole-genome sequencing analysis indicated that the isolated phage had a 42 813 bp long genome with 49.8% G + C content. Neither tRNA genes nor those associated with antibiotic resistance, virulence factors, or lysogenic formation were detected in the genome. The efficacy of E19 was evaluated in liquid eggs inoculated with S. Enteritidis at 4 and 25 °C, and results showed that it could effectively eradicate S. Enteritidis in just 30 min and prevented its growth up to 72 h. Our findings indicate that E19 can be an alternative to a preservative to control Salmonella in food samples and help prevent and treat salmonellosis.

Decoding the Structure-Function Relationship of the Muramidase Domain in E. coli O157.H7 Bacteriophage Endolysin: A Potential Building Block for Chimeric Enzybiotics

Bacteriophage endolysins are potential alternatives to conventional antibiotics for treating multidrug-resistant gram-negative bacterial infections. However, their structure-function relationships are poorly understood, hindering their optimization and application. In this study, we focused on the individual functionality of the C-terminal muramidase domain of Gp127, a modular endolysin from E. coli O157:H7 bacteriophage PhaxI. This domain is responsible for the enzymatic activity, whereas the N-terminal domain binds to the bacterial cell wall. Through protein modeling, docking experiments, and molecular dynamics simulations, we investigated the activity, stability, and interactions of the isolated C-terminal domain with its ligand. We also assessed its expression, solubility, toxicity, and lytic activity using the experimental data. Our results revealed that the C-terminal domain exhibits high activity and toxicity when tested individually, and its expression is regulated in different hosts to prevent self-destruction. Furthermore, we validated the muralytic activity of the purified refolded protein by zymography and standardized assays. These findings challenge the need for the N-terminal binding domain to arrange the active site and adjust the gap between crucial residues for peptidoglycan cleavage. Our study shed light on the three-dimensional structure and functionality of muramidase endolysins, thereby enriching the existing knowledge pool and laying a foundation for accurate in silico modeling and the informed design of next-generation enzybiotic treatments.

Genomic and Proteomic Analysis of Six Vi01-like Phages Reveals Wide Host Range and Multiple Tail Spike Proteins

Enterobacteriaceae is a large family of Gram-negative bacteria composed of many pathogens, including Salmonella and Shigella. Here, we characterize six bacteriophages that infect Enterobacteriaceae, which were isolated from wastewater plants in the Wasatch front (Utah, United States). These phages are highly similar to the Kuttervirus vB_SenM_Vi01 (Vi01), which was isolated using wastewater from Kiel, Germany. The phages vary little in genome size and are between 157 kb and 164 kb, which is consistent with the sizes of other phages in the Vi01-like phage family. These six phages were characterized through genomic and proteomic comparison, mass spectrometry, and both laboratory and clinical host range studies. While their proteomes are largely unstudied, mass spectrometry analysis confirmed the production of five hypothetical proteins, several of which unveiled a potential operon that suggests a ferritin-mediated entry system on the Vi01-like phage family tail. However, no dependence on this pathway was observed for the single host tested herein. While unable to infect every genus of Enterobacteriaceae tested, these phages are extraordinarily broad ranged, with several demonstrating the ability to infect Salmonella enterica and Citrobacter freundii strains with generally high efficiency, as well as several clinical Salmonella enterica isolates, most likely due to their multiple tail fibers.

Isolation, characterization, and genome analysis of a broad host range Salmonella phage vB_SenS_TUMS_E4: a candidate bacteriophage for biocontrol

Salmonella enteritidis is one of the most important foodborne pathogens that cause numerous outbreaks worldwide. Some strains of Salmonella have become progressively resistant to antibiotics, so they could represent a critical threat to public health and have led to the use of alternative therapeutic approaches like phage therapy. In this study, a lytic phage, vB_SenS_TUMS_E4 (E4), was isolated from poultry effluent and characterized to evaluate its potential and efficacy for bio-controlling S. enteritidis in foods. Transmission electron microscopy revealed that E4 has a siphovirus morphotype, with an isometric head and non-contractile tail. Determining the host range showed that this phage can effectively infect different motile as well as non-motile Salmonella enterica serovars. The biological characteristics of E4 showed that it has a short latent period of about 15 min and a large burst size of 287 PFU/cell, and is also significantly stable in a broad range of pHs and temperatures. The E4 whole genome contains 43,018 bp and encodes 60 coding sequences (CDSs) but no tRNA genes. Bioinformatics analysis revealed that the genome of E4 lacks any genes related to lysogeny behavior, antibiotic resistance, toxins, or virulence factors. The efficacy of phage E4 as a bio-control agent was assessed in various foodstuffs inoculated with S. enteritidis at 4°C and 25°C, and the resulting data indicated that it could eradicate S. enteritidis after a very short time of 15 min. The findings of the present study showed that E4 is a hopeful candidate as a bio-control agent against S. enteritidis and has the potential to be used in various foodstuffs.

Bacteriophage-based biocontrol technology to enhance the efficiency of wastewater treatment and reduce targeted bacterial biofilms

Wastewater treatment is an essential process for public health and a sustainable ecosystem. Inadequate wastewater treatment can lead to the release of organic and inorganic pollutants and pathogenic bacteria into the receiving waters which could be further utilized for recreation purposes. The interaction between bacteriophage and bacteria in a wastewater treatment plant plays a major role in maintaining the treatment process. Phage therapy has been proposed as an alternative to conventional treatment methods as bacteriophages can be used on specific targets and leave useful bacteria unharmed. The bacterial species, which are responsible for bulking, foaming, and biofilm formation in a wastewater treatment plant (WWTP) have been identified and their respective phages are isolated to control their growth. Phages with lytic life cycles are preferred to lysogenic. Lytic phages can kill the specific target as they lyse the cell, infect most of the hosts, and have an immediate effect on controlling problems caused by bacteria in a WWTP. The bacteriophages such as T7, SPI1, GTE7, PhaxI, MAG1, MAG2, ϕPh_Se01, ϕPh_Se02, and Bxb1 have been investigated for the removal of bacterial biofilms from wastewater. Novel experimental setups have improved the efficiency of phage therapy in small-scale and pilot-scale experiments. Much more in-depth knowledge of the microbial community and their interaction would help promote the usage of phage therapy in large-scale wastewater treatments. This paper has covered the recent advancements in phage therapy as an effective biocontrol of pathogenic bacteria in the wastewater treatment process and has looked at certain shortcomings that have to be improved.

Isolating and sequencing vB_Kpn_3, a lytic bacteriophage against multidrug-resistant Klebsiella pneumoniae

Aim: Phage therapy, as an effective and specific method in the treatment of multidrug-resistant (MDR) bacterial infections, has attracted the attention of many researchers. Methods and results: In this study, a double-stranded DNA phage with the ability of lysing some strains of MDR Klebsiella pneumoniae (vB_Kpn_3) was isolated from hospitals' wastewater and then characterized morphologically and genetically. Transmission electron microscopy and genetic analyses have revealed that vB_Kpn_3 is a member of Siphoviridae family. One-step growth curve also showed a burst time of 35 min and a burst size of 31 PFU/ml. The genome of the phage is composed of 112,080 bp with 41.33% G + C content carrying 186 open reading frames. Conclusion: vB_Kpn_3 is a broad host range phage that infects MDR K. pneumoniae and some other species of Enterobacteriaceae such as Escherichia coli and Salmonella typhi. In addition, no antibiotic resistance and toxin genes were detected in its genome.

vB-Ea-5: a lytic bacteriophage against multi-drug-resistant Enterobacter aerogenes

Background and Objectives:

Multi-drug-resistant Enterobacter aerogenes is associated with various infectious diseases that cannot be easily treated by antibiotics. However, bacteriophages have potential therapeutic applications in the control of multi-drug-resistant bacteria. In this study, we aimed to isolate and characterize of a lytic bacteriophage that can lyse specifically the multi-drug-resistant (MDR) E. aerogenes.

Materials and Methods:

Lytic bacteriophage was isolated from Qaem hospital wastewater and characterized morphologically and genetically. Next-generation sequencing was used to complete genome analysis of the isolated bacteriophage.

Results:

Based on the transmission electron microscopy feature, the isolated bacteriophage (vB-Ea-5) belongs to the family Myoviridae. vB-Ea-5 had a latent period of 25 minutes, a burst size of 13 PFU/ml, and a burst time of 40 min. Genome sequencing revealed that vB-Ea-5 has a 135324 bp genome with 41.41% GC content. The vB-Ea-5 genome codes 212 ORFs 90 of which were categorized into several functional classes such as DNA replication and modification, transcriptional regulation, packaging, structural proteins, and a host lysis protein (Holin). No antibiotic resistance and toxin genes were detected in the genome. SDS-PAGE of vB-Ea-5 proteins exhibited three major and four minor bands with a molecular weight ranging from 18 to 50 kD.

Conclusion:

Our study suggests vB-Ea-5 as a potential candidate for phage therapy against MDR E. aerogenes infections.

Subtypes of tail spike proteins predicts the host range of Ackermannviridae phages

Phages belonging to the Ackermannviridae family encode up to four tail spike proteins (TSPs), each recognizing a specific receptor of their bacterial hosts. Here, we determined the TSPs diversity of 99 Ackermannviridae phages by performing a comprehensive in silico analysis. Based on sequence diversity, we assigned all TSPs into distinctive subtypes of TSP1, TSP2, TSP3 and TSP4, and found each TSP subtype to be specifically associated with the genera (Kuttervirus, Agtrevirus, Limestonevirus, Taipeivirus) of the Ackermannviridae family. Further analysis showed that the N-terminal XD1 and XD2 domains in TSP2 and TSP4, hinging the four TSPs together, are preserved. In contrast, the C-terminal receptor binding modules were only conserved within TSP subtypes, except for some Kuttervirus TSP1s and TSP3s that were similar to specific TSP4s. A conserved motif in TSP1, TSP3 and TSP4 of Kuttervirus phages may allow recombination between receptor binding modules, thus altering host recognition. The receptors for numerous uncharacterized phages expressing TSPs in the same subtypes were predicted using previous host range data. To validate our predictions, we experimentally determined the host recognition of three of the four TSPs expressed by kuttervirus S117. We confirmed that S117 TSP1 and TSP2 bind to their predicted host receptors, and identified the receptor for TSP3, which is shared by 51 other Kuttervirus phages. Kuttervirus phages were thus shown encode a vast genetic diversity of potentially exchangeable TSPs influencing host recognition. Overall, our study demonstrates that comprehensive in silico and host range analysis of TSPs can predict host recognition of Ackermannviridae phages.

Identification and characterization of lytic bacteriophages specific to foodborne pathogenic Escherichia coli O157:H7

The objective of this study was to identify and characterize five different lytic bacteriophages specific to Escherichia coli O157:H7. vB_EcoM-P12, vB_EcoM-P13, vB_EcoM-P23, and vB_EcoM-P34 phages belonged to the Myoviridae family and vB_EcoS-P24 phage was in the Siphoviridae family. Their plaque sizes changed between 0.48 ± 0.03 and 0.90 ± 0.03 mm in diameter. stx1 and stx2 virulent gene regions were absent in the genome of five Eco-phages and their genome size was 33 kbp. The protein band profiles of the five phages were found to be different from each other. Their latent period, burst size, and burst time changed between 10-15 min, 72-144 PFU/cell and 20-35 min, respectively. Multiplicity of infection values and mutant frequency of the phages were among 0.1-0.001 and 1.14 × 10^-7-3.69 × 10^-8, respectively. The phages had strong lytic activity against their host bacteria (E. coli NCTC 12900, ATCC 43888, and ATCC 35150) at 5-37 ℃ and adsorbed to their host cells by 92.7-97.5% in the first five minutes of incubation. These phages are thought to be good candidates as therapeutic and biocontrol agents against E. coli O157:H7 in the veterinary science and food industry due to short latent period, high burst size, rapid development in host cells, high lytic activity, high adsorption rate, stability over a wide pH range and high temperature, and absence of stx1 and stx2 genes.

An Overview of the Elusive Passenger in the Gastrointestinal Tract of Cattle: The Shiga Toxin Producing Escherichia coli

For approximately 10,000 years, cattle have been our major source of meat and dairy. However, cattle are also a major reservoir for dangerous foodborne pathogens that belong to the Shiga toxin-producing Escherichia coli (STEC) group. Even though STEC infections in humans are rare, they are often lethal, as treatment options are limited. In cattle, STEC infections are typically asymptomatic and STEC is able to survive and persist in the cattle GIT by escaping the immune defenses of the host. Interactions with members of the native gut microbiota can favor or inhibit its persistence in cattle, but research in this direction is still in its infancy. Diet, temperature and season but also industrialized animal husbandry practices have a profound effect on STEC prevalence and the native gut microbiota composition. Thus, exploring the native cattle gut microbiota in depth, its interactions with STEC and the factors that affect them could offer viable solutions against STEC carriage in cattle.

Isolation, Characterization and Genomic Analysis of a Novel Bacteriophage VB_EcoS-Golestan Infecting Multidrug-Resistant Escherichia coli Isolated from Urinary Tract Infection

Escherichia coli (E. coli) is one of the most common uropathogenic bacteria. The emergence of multi-drug resistance among these bacteria resulted in a worldwide public health problem which requires alternative treatment approaches such as phage therapy. In this study, phage VB_EcoS-Golestan, a member of Siphoviridae family, with high lytic ability against E. coli isolates, was isolated from wastewater. Its burst size was large and about 100 plaque-forming units/infected cell, rapid adsorption time, and high resistance to a broad range of pH and temperatures. Bioinformatics analysis of the genomic sequence suggests that VB_EcoS-Golestan is a new phage closely related to Escherichia phages in the Kagunavirus genus, Guernseyvirinae subfamily of Siphoviridae. The genome size was 44829 bp bp that encodes 78 putative ORFs, no tRNAs, 7 potential promoter sequences and 13 Rho-factor-independent terminators. No lysogenic mediated genes were detected in VB_EcoS-Golestan genome. Overall VB_EcoS-Golestan might be used as a potential treatment approach for controlling E. coli mediated urinary tract infection, however, further studies are essential to ensure its safety.

Diversity and Host Specificity Revealed by Biological Characterization and Whole Genome Sequencing of Bacteriophages Infecting Salmonella enterica

Phages infecting members of the opportunistic human pathogen, Salmonella enterica, are widespread in natural environments and offer a potential source of agents that could be used for controlling populations of this bacterium; yet, relatively little is known about these phages. Here we describe the isolation and characterization of 45 phages of Salmonella enterica from disparate geographic locations within British Columbia, Canada. Host-range profiling revealed host-specific patterns of susceptibility and resistance, with several phages identified that have a broad-host range (i.e., able to lyse >40% of bacterial hosts tested). One phage in particular, SE13, is able to lyse 51 out of the 61 Salmonella strains tested. Comparative genomic analyses also revealed an abundance of sequence diversity in the sequenced phages. Alignment of the genomes grouped the phages into 12 clusters with three singletons. Phages within certain clusters exhibited extraordinarily high genome homology (>98% nucleotide identity), yet between clusters, genomes exhibited a span of diversity (<50% nucleotide identity). Alignment of the major capsid protein also supported the clustering pattern observed with alignment of the whole genomes. We further observed associations between genomic relatedness and the site of isolation, as well as genetic elements related to DNA metabolism and host virulence. Our data support the knowledge framework for phage diversity and phage-host interactions that are required for developing phage-based applications for various sectors, including biocontrol, detection and typing.

A major-capsid-protein-based multiplex PCR assay for rapid identification of selected virulent bacteriophage types

Bacteriophages represent a promising alternative for controlling pathogenic bacteria. They are ubiquitous in the environment, and their isolation is usually simple and fast. However, not every phage is suitable for biocontrol applications. It must be virulent (i.e., strictly lytic), non-transducing, and safe. We have developed a method for identifying selected types of virulent phages at an early stage of the isolation process to simplify the search for suitable candidates. Using the major capsid protein (MCP) as a phylogenetic marker, we designed degenerate primers for the identification of Felix O1-, GJ1-, N4-, SP6-, T4-, T7-, and Vi1-like phages in multiplex PCR setups with single phage plaques as templates. Performance of the MCP PCR assay was evaluated with a set of 26 well-characterized phages. Neither false-positive nor false-negative results were obtained. In addition, 154 phages from enrichment cultures from various environmental samples were subjected to MCP PCR analysis. Eight of them, specific for Salmonella enterica, Escherichia coli, or Erwinia amylovora, belonged to one of the selected phage types. Their PCR-based identification was successfully confirmed by pulsed-field gel electrophoresis of the phage genomes, electron microscopy, and sequencing of the amplified mcp gene fragment. The MCP PCR assay was shown to be a simple method for preliminary assignment of new phages to a certain group and thus to identify candidates for biocontrol immediately after their isolation. Given that sufficient sequence data are available, this method can be extended to any phage group of interest.

Isolation and Complete Genome Sequence of a Novel Marinobacter Phage B23

We used the double-agar layer method to isolate a novel Marinobacter marina bacteriophage, B23, from the surface water sample of the Bohai sea of China. There is some work to better understand the phage. The result of transmission electron microscopy revealed that B23 belongs to the family Siphoviridae with a head of 80 nm in diameter and a tail of 230 nm. Microbiological characterization evidenced that phage B23 is stable at the temperatures from - 25 to 60 °C, and showed vigorous vitality at pH between 4.0 and 12.0. One-step growth experiment showed that it had a longer latent period and higher lysis efficiency. Furthermore, the complete genome of B23 was sequenced and analyzed, which consists of a 35132 bp DNA with a G + C content of 59.8% and 50 putative open reading frames. The genome was divided into five parts, consisting of DNA replication and regulation, phage packaging, phage structure, host lysis and hypothetical protein.

Identification and biosynthesis of thymidine hypermodifications in the genomic DNA of widespread bacterial viruses

Certain viruses of bacteria (bacteriophages) enzymatically hypermodify their DNA to protect their genetic material from host restriction endonuclease-mediated cleavage. Historically, it has been known that virion DNAs from the Delftia phage ΦW-14 and the Bacillus phage SP10 contain the hypermodified pyrimidines α-putrescinylthymidine and α-glutamylthymidine, respectively. These bases derive from the modification of 5-hydroxymethyl-2'-deoxyuridine (5-hmdU) in newly replicated phage DNA via a pyrophosphorylated intermediate. Like ΦW-14 and SP10, the Pseudomonas phage M6 and the Salmonella phage ViI encode kinase homologs predicted to phosphorylate 5-hmdU DNA but have uncharacterized nucleotide content [Iyer et al. (2013) Nucleic Acids Res 41:7635-7655]. We report here the discovery and characterization of two bases, 5-(2-aminoethoxy)methyluridine (5-NeOmdU) and 5-(2-aminoethyl)uridine (5-NedU), in the virion DNA of ViI and M6 phages, respectively. Furthermore, we show that recombinant expression of five gene products encoded by phage ViI is sufficient to reconstitute the formation of 5-NeOmdU in vitro. These findings point to an unexplored diversity of DNA modifications and the underlying biochemistry of their formation.

Visualization of Phage Genomic Data: Comparative Genomics and Publication-Quality Diagrams

The presentation of bacteriophage genomes as diagrams allows the location and organization of features to be communicated in a clear and effective manner. A wide range of software applications are available for the clear and accurate visualization of genomic data. Several of these applications incorporate comparative analysis tools, allowing for insertions, deletions, rearrangements and variations in syntenic regions to be visualized. In this chapter, freely available software and resources for the generation of high-quality graphical maps of bacteriophage genomes are listed and discussed.

A minireview on the in vitro and in vivo experiments with anti-Escherichia coli O157:H7 phages as potential biocontrol and phage therapy agents

Phage therapy is an old method of combating bacterial pathogens that has recently been taken into consideration due to the alarming spread of antibiotic resistance. Escherichia coli O157:H7 is a foodborne pathogen that causes hemorrhagic colitis and life-threatening Hemolytic Uremic Syndrome (HUS). There are several studies on isolation of specific phages against E. coli O157:H7 and more than 60 specific phages have been published so far. Although in vitro experiments have been successful in elimination or reduction of E. coli O157:H7numbers, in vivo experiments have not been as promising. This may be due to escape of bacteria to locations where phages have difficulties to enter or due to the adverse conditions in the gastrointestinal tract that affect phage viability and proliferation. To get around the latter obstacle, an alternative phage delivery method such as polymer microencapsulation should be tried. While the present time results are not very encouraging the work should be continued as more efficient phage treatment regimens might be found in future.

Genome Sequence of the Enterohemorrhagic Escherichia coli Bacteriophage UFV-AREG1

Here, we present the genome sequence of the Escherichia coli bacteriophage UFV-AREG1. This phage was isolated from cowshed wastewater and showed specificity for enterohemorrhagic E. coli O157:H7 (ATCC 43895), E. coli 0111 (CDC O11ab) and E. coli (ATCC 23229).

Characterization of a new ViI-like Erwinia amylovora bacteriophage phiEa2809

Erwinia amylovora is a Gram-negative plant pathogenic bacteria causing fire blight disease in many Rosaceae species. A novel E. amylovora bacteriophage, phiEa2809, was isolated from symptomless apple leaf sample collected in Belarus. This phage was also able to infect Pantoea agglomerans strains. The genome of phiEa2809 is a double-stranded linear DNA 162,160 bp in length, including 145 ORFs and one tRNA gene. The phiEa2809 genomic sequence is similar to the genomes of the Serratia plymutica phage MAM1, Shigella phage AG-3, Dickeya phage vB DsoM LIMEstone1 and Salmonella phage ViI and lacks similarity to described E. amylovora phage genomes. Based on virion morphology (an icosahedral head, long contractile tail) and genome structure, phiEa2809 was classified as a member of Myoviridae, ViI-like bacteriophages group. PhiEa2809 is the firstly characterized ViI-like bacteriophage able to lyse E. amylovora.

Escherichia coli O157:H7 bacteriophage Φ241 isolated from an industrial cucumber fermentation at high acidity and salinity

A novel phage, Φ241, specific for Escherichia coli O157:H7 was isolated from an industrial cucumber fermentation where both acidity (pH ≤ 3.7) and salinity (≥5% NaCl) were high. The phage belongs to the Myoviridae family. Its latent period was 15 min and average burst size was 53 phage particles per infected cell. The phage was able to lyse 48 E. coli O157:H7 strains, but none of the 18 non-O157 strains (including E. coli O104:H7) or the 2 O antigen-negative mutants of O157:H7 strain, 43895Δper (also lacking H7 antigen) and F12 (still expressing H7 antigen). However, the phage was able to lyse a per-complemented strain (43895ΔperComp) which expresses O157 antigen. These results indicated that phage Φ241 is specific for O157 antigen, and E. coli strains lacking O157 antigen were resistant to the phage infection, regardless of the presence or absence of H7 antigen. SDS-PAGE profile revealed at least 13 structural proteins of the phage. The phage DNA was resistant to many commonly used restriction endonucleases, suggesting the presence of modified nucleotides in the phage genome. At the multiplicity of infection of 10, 3, or 0.3, the phage caused a rapid cell lysis within 1 or 2 h, resulting in 3.5- or 4.5-log-unit reduction in cell concentration. The high lytic activity, specificity and tolerance to low pH and high salinity make phage Φ241 a potentially ideal biocontrol agent of E. coli O157:H7 in various foods. To our knowledge, this is the first report on E. coli O157:H7 phage isolated from high acidity and salinity environment.

Viunalikeviruses are environmentally common agents of horizontal gene transfer in pathogens and biocontrol bacteria

Bacteriophages have been used as natural biocontrol and therapeutic agents, but also as biotechnological tools for bacterial engineering. We showed recently that the transducing bacteriophage ϕMAM1 is a ViI-like phage and a member of the new genus, ‘Viunalikevirus'. Here, we show that four additional ViI-like phages and three new environmentally isolated viunalikeviruses, all infecting plant and human pathogens, are very efficient generalised transducers capable of transducing chromosomal markers at frequencies of up to 10⁻⁴ transductants per plaque-forming unit. We also demonstrate the interstrain transduction of plasmids and chromosomal markers, including genes involved in anabolism, genes for virulence and genes encoding secondary metabolites involved in biocontrol. We propose that all viunalikeviruses are likely to perform efficient horizontal gene transfer. Viunalikeviruses therefore represent useful agents for functional genomics and bacterial engineering, and for chemical and synthetic biology studies, but could be viewed as inappropriate choices for phage therapy.

Bacteriophage ϕMAM1, a viunalikevirus, is a broad-host-range, high-efficiency generalized transducer that infects environmental and clinical isolates of the enterobacterial genera Serratia and Kluyvera

Members of the enterobacterial genus Serratia are ecologically widespread, and some strains are opportunistic human pathogens. Bacteriophage ϕMAM1 was isolated on Serratia plymuthica A153, a biocontrol rhizosphere strain that produces the potently bioactive antifungal and anticancer haterumalide oocydin A. The ϕMAM1 phage is a generalized transducing phage that infects multiple environmental and clinical isolates of Serratia spp. and a rhizosphere strain of Kluyvera cryocrescens. Electron microscopy allowed classification of ϕMAM1 in the family Myoviridae. Bacteriophage ϕMAM1 is virulent, uses capsular polysaccharides as a receptor, and can transduce chromosomal markers at frequencies of up to 7 × 10(-6) transductants per PFU. We also demonstrated transduction of the complete 77-kb oocydin A gene cluster and heterogeneric transduction of a plasmid carrying a type III toxin-antitoxin system. These results support the notion of the potential ecological importance of transducing phages in the acquisition of genes by horizontal gene transfer. Phylogenetic analyses grouped ϕMAM1 within the ViI-like bacteriophages, and genomic analyses revealed that the major differences between ϕMAM1 and other ViI-like phages arise in a region encoding the host recognition determinants. Our results predict that the wider genus of ViI-like phages could be efficient transducing phages, and this possibility has obvious implications for the ecology of horizontal gene transfer, bacterial functional genomics, and synthetic biology.

Complete genome sequence of 285P, a novel T7-like polyvalent E. coli bacteriophage

Bacteriophages are considered potential biological agents for the control of infectious diseases and environmental disinfection. Here, we describe a novel T7-like polyvalent Escherichia coli bacteriophage, designated "285P," which can lyse several strains of E. coli. The genome, which consists of 39,270 base pairs with a G+C content of 48.73 %, was sequenced and annotated. Forty-three potential open reading frames were identified using bioinformatics tools. Based on whole-genome sequence comparison, phage 285P was identified as a novel strain of subgroup T7. It showed strongest sequence similarity to Kluyvera phage Kvp1. The phylogenetic analyses of both non-structural proteins (endonuclease gp3, amidase gp3.5, DNA primase/helicase gp4, DNA polymerase gp5, and exonuclease gp6) and structural protein (tail fiber protein gp17) led to the identification of 285P as T7-like phage. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analyses verified the annotation of the structural proteins (major capsid protein gp10a, tail protein gp12, and tail fiber protein gp17).