The life cycle of SPß and related phages.

Phages are viruses of bacteria and are the smallest and most common biological entities in the environment. They can reproduce immediately after infection or integrate as a prophage into their host genome. SPß is a prophage of the Gram-positive model organism Bacillus subtilis 168, and it has been known for more than 50 years. It is sensitive to dsDNA damage and is induced through exposure to mitomycin C or UV radiation. When induced from the prophage, SPß requires 90 min to produce and release about 30 virions. Genomes of sequenced related strains range between 128 and 140 kb, and particle-packed dsDNA exhibits terminal redundancy. Formed particles are of the Siphoviridae morphotype. Related isolates are known to infect other B. subtilis clade members. When infecting a new host, SPß presumably follows a two-step strategy, adsorbing primarily to teichoic acid and secondarily to a yet unknown factor. Once in the host, SPß-related phages pass through complex lysis-lysogeny decisions and either enter a lytic cycle or integrate as a dormant prophage. As prophages, SPß-related phages integrate at the host chromosome's replication terminus, and frequently into the spsM or kamA gene. As a prophage, it imparts additional properties to its host via phage-encoded proteins. The most notable of these functional proteins is sublancin 168, which is used as a molecular weapon by the host and ensures prophage maintenance. In this review, we summarise the existing knowledge about the biology of the phage regarding its life cycle and discuss its potential as a research object.

Identification of proteins associated with two diverse Caulobacter phicbkvirus particles.

Genomic evolution among bacteriophages infecting Caulobacter crescentus is inevitable. However, the conservation of the proteins associated with intact phage particles has not been investigated. In this study, we compared the structural proteins associated with two genomically diverse but morphologically similar C. crescentus-infecting bacteriophages, phiCbK and CcrSC. We were able to detect more than 20 proteins that are part of the bacteriophage particle in both phages, and we were able to identify a small number of proteins that were found in only one of the two phage particles. All but one of the genes coding for these structural proteins were located in a region of the genome that had been designated a structural region, confirming the idea that the genes in these phage genomes are clustered according to their function. During the purification process, we also discovered that phiCbk has a replication complex that can be recovered from the cell lysate, and this complex allowed us to identify many of the phage proteins involved in phage genome replication.

The varying effects of a range of preservatives on Myoviridae and Siphoviridae bacteriophages formulated in a semi-solid cream preparation.

Bacteriophages may be formulated into semi-solid bases for therapeutic delivery. This work investigated the effects of a range of preservatives on the viability of Myoviridae and Siphoviridae bacteriophages when these were formulated into a standard semi-solid cream base. The six preservatives tested included: benzoic acid (0·1%), chlorocresol (0·1%), combination hydroxybenzoates (propyl 4-hydroxybenzoates with methyl 4-hydroxybenzoates) (0·1%), methyl 4-hydroxybenzoate (0·08%), 2-phenoxyethanol (1%) and propyl 4-hydroxybenzoate (0·02%). These were each formulated into cetomacrogol cream aqueous to generate six individual semi-solid bases into which Myoviridae and Siphoviridae bacteriophages were added and tested for stability. Optimal bacteriophage stability was seen when the preservative chlorocresol was used. Bacteriophage in the acidic benzoic acid were the least stable, resulting in complete loss of viability after 4-5 weeks. Of the bacteriophages tested, the Myoviridae KOX1 was significantly more stable than the Siphoviridae PAC1 after 91 days in formulations with each of the preservatives. Our results suggest the need for individual testing of specific bacteriophages in pharmaceutical formulations, as their efficacy when exposed to preservatives and excipients in these delivery forms may vary. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteriophages are being increasingly investigated as alternatives to antibiotics. While bacteriophages can be formulated in diverse ways for therapeutic delivery, there has been scant work on how excipients and preservatives in these formulations affect stability of different bacteriophages. We demonstrate that the nature of preservatives in formulations will affect bacteriophage stability, and that in these formulations, viability of bacteriophage differs according to their morphology. Our work highlights the need for individual testing of specific bacteriophages in pharmaceutical formulations, as efficacy when exposed to preservatives and excipients in these delivery forms may vary.

Potential use of newly isolated bacteriophage as a biocontrol against Acidovorax citrulli.

Acidovorax citrulli, the gram-negative bacteria that causes bacterial fruit blotch (BFB), has been responsible for huge worldwide economic losses in watermelon and melon production since 1980. No commercial cultivar resistant to BFB has been reported. Of the two reported genotypes of A. citrulli, genotype I is the main causal agent of BFB in melon and genotype II causes disease in watermelon. After the isolation of the first bacteriophage against A. citrulli (ACP17), efforts have been made to isolate bacteriophages with wider host ranges by collecting samples from watermelon, pumpkin, and cucumber. The newly isolated phage ACPWH, belonging to the Siphoviridae family, has a head size of 60 ± 5 nm and tail size of 180 ± 5 nm, and can infect 39 out of 42 A. citrulli strains. ACPWH has genome size of 42,499 and GC content of 64.44%. Coating watermelon seeds with bacteriophage ACPWH before soil inoculation with A. citrulli resulted in 96% germination and survival, compared to 13% germination of uncoated control seeds. These results suggest that phage ACPWH may be an effective and low-cost biocontrol agent against BFB.

A newly isolated roseophage represents a distinct member of Siphoviridae family.

BACKGROUND: Members of the Roseobacter lineage are a major group of marine heterotrophic bacteria because of their wide distribution, versatile lifestyles and important biogeochemical roles. Bacteriophages, the most abundant biological entities in the ocean, play important roles in shaping their hosts' population structures and mediating genetic exchange between hosts. However, our knowledge of roseophages (bacteriophages that infect Roseobacter) is far behind that of their host counterparts, partly reflecting the need to isolate and analyze the phages associated with this ecologically important bacterial clade. METHODS: vB_DshS-R4C (R4C), a novel virulent roseophage that infects Dinoroseobacter shibae DFL12T, was isolated with the double-layer agar method. The phage morphology was visualized with transmission electron microscopy. We characterized R4C in-depth with a genomic analysis and investigated the distribution of the R4C genome in different environments with a metagenomic recruitment analysis. RESULTS: The double-stranded DNA genome of R4C consists of 36,291 bp with a high GC content of 66.75%. It has 49 genes with low DNA and protein homologies to those of other known phages. Morphological and phylogenetic analyses suggested that R4C is a novel member of the family Siphoviridae and is most closely related to phages in the genus Cronusvirus. However, unlike the Cronusvirus phages, R4C encodes an integrase, implying its ability to establish a lysogenic life cycle. A terminal analysis shows that, like that of λ phage, the R4C genome utilize the 'cohesive ends' DNA-packaging mechanism. Significantly, homologues of the R4C genes are more prevalent in coastal areas than in the open ocean. CONCLUSIONS: Information about this newly discovered phage extends our understanding of bacteriophage diversity, evolution, and their roles in different environments.

Isolation, characterization, and PCR-based molecular identification of a siphoviridae phage infecting Shigella dysenteriae.

BACKGROUND: Shigella dysenteriae is one of the members of Shigella genus which was the main responsible of different Shigellosis outbreaks worldwide. The increasing consumption of antibiotics has led to the emergence and spreading of antibiotic-resistant strains. Therefore, finding new alternatives for infection control is essential, one of which is using bacteriophages. MATERIALS AND METHODS: Lytic bacteriophage against Shigella dysenteriae was isolated from petroleum refinery wastewater. Phage morphological and genetic characteristics were studied using TEM, and sequencing, respectively. In addition, the genome size was estimated, and phage resistance to different temperatures and pH, host range, adsorption rate, and one-step growth were investigated. RESULTS: According to the morphology and genetic results, this phage was named vB-SdyS-ISF003. Sequencing of the PCR products revealed that the vB-SdyS-ISF003 phage belongs to the species T1virus, subfamily Tunavirinae of family Siphoviridae. This was the first detected bacteriophage against S. dysenteriae, which belongs to the family Siphoviridae. In addition, its host range was limited to S. dysenteriae. The genome size was about 62 kb. vB-SdyS-ISF003 phage has a number of desirable characteristics including the limited host range to S. dysenteriae, very short connection time, a relatively wide range of temperature tolerance -20 to 50 °C, pH tolerance of 7-9 without significant reduction in the phage titer. CONCLUSION: vB-SdyS-ISF003 is a novel virulent T1virus phage and has the appropriate potential for being used in bio controlling of S. dysenteriae in different condition.

Characterization and genome analysis of the temperate bacteriophage φSAJS1 from Streptomyces avermitilis.

Streptomyces is an important antibiotic-producing bacterium; however, antibiotic production is often negatively affected by bacteriophage contamination. In the present study, the temperate phage φSAJS1 was isolated and characterized from an unsuccessful Streptomyces avermitilis fermentation culture. The complete genome of phage φSAJS1 was sequenced. Phage φSAJS1 belongs to the Siphoviridae family based on its morphology as determined by transmission electron microscopy. Host range analysis indicated that phage φSAJS1 specifically infects various S. avermitilis strains. One-step growth curve assays revealed that Ca2+ is required for abundant phage proliferation and that phage φSAJS1 is resistant to high temperatures (70 °C) and alkaline solutions (pH 11). The phage φSAJS1 genome is a circular double-stranded (ds) DNA that does not contain terminal repeats and cohensive ends, thereby suggesting a headful DNA packaging mechanism. The whole phage φSAJS1 genome is 56,451 bp in length with a high GC-content (68.3%) and encodes 76 putative open reading frames. Similarity analysis showed that the majority of the candidate proteins share high similarity (50%-72%) to proteins in the S. griseus subsp. phages YDN12 and TP1604, indicating either a common origin or more recent DNA recombination events throughout the evolution of these three phage lineages.

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.

Isolation and characterization of a novel phage Xoo-sp2 that infects Xanthomonas oryzae pv. oryzae.

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a serious bacterial disease in rice-growing regions worldwide. Phage therapy has been proposed as a potential measure to treat bacterial infections. In this study, a novel phage, Xoo-sp2, which infects Xoo was isolated from soil. The characteristics of Xoo-sp2, including the morphology, one-step growth curve and host range, were analysed. The genome of phage Xoo-sp2 was sequenced and annotated. The results demonstrated that Xoo-sp2 is a siphovirus and has a broad lytic spectrum, infecting 9 out of 10 representative Xoo strains. Genome analysis showed that the Xoo-sp2 genome consists of a linear double-stranded DNA molecule of length 60 370 bp. Annotation of the whole genome indicated that Xoo-sp2 encodes 79 putative open reading frames (ORFs). Comparative genomics analysis of Xoo-sp2 showed that it shares significant similarity only with Pseudomonas and Stenotrophomonas phages (with maximum identity reaching 80 % along 69 % of the genome), and thus represents a novel Xanthomonas phage. Xoo-sp2 significantly inhibited Xoo growth in liquid culture. An experiment with potted plants indicated that Xoo-sp2 could efficiently control BLB in living rice. In summary, our work characterized a novel Xanthomonas phage and demonstrated its potential as a prophylactic agent in the control of BLB in rice.

Production of Bacteriophages by Listeria Cells Entrapped in Organic Polymers.

Applications for bacteriophages as antimicrobial agents are increasing. The industrial use of these bacterial viruses requires the production of large amounts of suitable strictly lytic phages, particularly for food and agricultural applications. This work describes a new approach for phage production. Phages H387 (Siphoviridae) and A511 (Myoviridae) were propagated separately using Listeria ivanovii host cells immobilised in alginate beads. The same batch of alginate beads could be used for four successive and efficient phage productions. This technique enables the production of large volumes of high-titer phage lysates in continuous or semi-continuous (fed-batch) cultures.

Characterization and genomic analyses of Aeromonas hydrophila phages AhSzq-1 and AhSzw-1, isolates representing new species within the T5virus genus.

In this study, two bacteriophage isolates, AhSzq-1 and AhSzw-1 that specifically infect Aeromonas hydrophila strain KT998822, were isolated from seawater and characterized. One-step growth curves showed that the latent period of AhSzq-1 and AhSzw-1 are 50 min and 60 min, respectively. The sequence similarities between AhSzq-1 and AhSzw-1 were 88% at the DNA and 83% at the protein level, suggesting that these two phages are representatives of two different species. The virion morphology, DNA genome size and terminal repeats of these two phages are similar to those of viruses classified as T5virus phages. Both phylogenetic analyses and proteomic comparison show that AhSzq-1 and AhSzw-1 group with members of the T5virus genus. We thus propose these two phages as representative isolates of two new species within the T5virus genus.

Genomics of Salmonella phage ΦStp1: candidate bacteriophage for biocontrol.

Multidrug-resistant Salmonella causing Salmonellosis is a food-borne pathogen and hence a public health hazard. Alternatives to antibiotics, such as phages, are possible solutions to this increasing drug resistance. In this context, several Salmonella phages were isolated and characterized. This paper describes the physiochemical and whole genome characterization of one such bacteriophage, ΦStp1, which efficiently infects serovars Salmonella Enteritidis and Salmonella Typhimurium. Morphological observations by transmission electron microscopy and phylogenetic analysis using terminase gene classified ΦStp1 to family Siphoviridae, closely resembling 'T5 like phage' morpho-types. With a maximum adsorption time of 50 min, ΦStp1 latent period was 30 min with 37 phages/cell burst size. ΦStp1 draft genome sequenced by shotgun method comprised 112,149 bp in 3 contigs with 37.99% GC content, 168 predicted ORFs, and 15 tRNAs. Genes involved in host shut down, DNA replication, regulation, nucleotide metabolism, lysis, and morphogenesis were also noted. The study not only provided an insight into the characteristics of phage genome, but also information about proteins encoded by bacteriophages, therefore contributing to understanding phage diversity. Sequence analysis also proved the absence of virulence and lysogeny-related genes, which only went to confirm ΦStp1 as a promising therapeutic agent against Salmonella infections.

In vitro activity of a combination of bacteriophages and antimicrobial plant extracts.

The continuing threat of antimicrobial resistance presents a considerable challenge to researchers to develop novel strategies ensuring that bacterial infections remain treatable. Many plant extracts have been shown to have antibacterial properties and could potentially be combined with other antibacterial agents to create more effective formulations. In this study, the antibacterial activity of three plant extracts and virulent bacteriophages have been assessed as individual components and in combination. When assessed with a modified suspension test, these plant extracts also exhibit antiviral activity at bacterial inhibitory concentrations. Hence, to investigate any potential additive effects between the extracts and virulent phages, the extracts were tested at subantiviral concentrations. Phages alone and in combination with plant extracts significantly reduced (P < 0·05) the bacterial concentration compared to untreated and extract treated controls up to 6 h (2-3log10 ), but this reduction did not extend to 24 h. In most cases, the phage and extract combinations did not significantly reduce bacterial content compared to phages alone. Additionally, there was little impact on the ability of the phages to reproduce within their bacterial hosts. To our knowledge, this study represents the first of its kind, in which antimicrobial plant extracts have been combined with virulent phages and has highlighted the necessity for plant extracts to be functionally characterized prior to the design of combinatorial therapies. Significance and Impact of Study This preliminary study provides insights into the potential combination of bacteriophages and antimicrobial plant bulk extracts to target bacterial pathogens. It is to our knowledge the first time in which virulent bacteriophages have been combined with antimicrobial plant extracts.

The First Siphoviridae Family Bacteriophages Infecting Bordetella bronchiseptica Isolated from Environment.

Bordetella bronchiseptica is a well-known etiological agent of kennel cough in dogs and cats and one of the two causative agents of atrophic rhinitis, a serious swine disease. The aim of the study was to isolate B. bronchiseptica bacteriophages from environmental samples for the first time. A total of 29 phages from 65 water samples were isolated using the strain ATCC 10580 as a host. The lytic spectra of the phages were examined at 25 and 37 °C, using 12 strains of B. bronchiseptica. All phages were able to plaque on 25.0 % to 41.7 % of the strains. The selected phages showed similar morphology (Siphoviridae, morphotype B2), but variation of RFLP patterns and efficacy of plating on various strains. The partial genome sequence of phage vB_BbrS_CN1 showed its similarity to phages from genus Yuavirus. Using PCR, it was confirmed that the phages do not originate from the host strain, and environmental origin was additionally confirmed by the analysis of host genome sequence in silico and plating heated and unheated samples in parallel. Accordingly, this is the first isolation of B. bronchiseptica phages from environment and the first isolation and characterization of phages of B. bronchiseptica belonging to family Siphoviridae.

Three novel bacteriophages isolated from the East African Rift Valley soda lakes.

BACKGROUND: Soda lakes are unique environments in terms of their physical characteristics and the biology they harbour. Although well studied with respect to their microbial composition, their viral compositions have not, and consequently few bacteriophages that infect bacteria from haloalkaline environments have been described. METHODS: Bacteria were isolated from sediment samples of lakes Magadi and Shala. Three phages were isolated on two different Bacillus species and one Paracoccus species using agar overlays. The growth characteristics of each phage in its host was investigated and the genome sequences determined and analysed by comparison with known phages. RESULTS: Phage Shbh1 belongs to the family Myoviridae while Mgbh1 and Shpa belong to the Siphoviridae family. Tetranucleotide usage frequencies and G + C content suggests that Shbh1 and Mgbh1 do not regularly infect, and have therefore not evolved with, the hosts they were isolated on here. Shbh1 was shown capable of infecting two different Bacillus species from the two different lakes demonstrating its potential broad-host range. Comparative analysis of their genome sequence with known phages revealed that, although novel, Shbh1 does share substantial amino acid similarity with previously described Bacillus infecting phages (Grass, phiNIT1 and phiAGATE) and belongs to the Bastille group, while Mgbh1 and Shpa are highly novel. CONCLUSION: The addition of these phages to current databases should help with metagenome/metavirome annotation efforts. We describe a highly novel Paracoccus infecting virus (Shpa) which together with NgoΦ6 and vB_PmaS_IMEP1 is one of only three phages known to infect Paracoccus species but does not show similarity to these phages.

Characterization of Functional Prophages in Clostridium difficile.

Bacteriophages (phages) are present in almost, if not all ecosystems. Some of these bacterial viruses are present as latent "prophages," either integrated within the chromosome of their host, or as episomal DNAs. Since prophages are ubiquitous throughout the bacterial world, there has been a sustained interest in trying to understand their contribution to the biology of their host. Clostridium difficile is no exception to that rule and with the recent release of hundreds of bacterial genome sequences, there has been a growing interest in trying to identify and classify these prophages. Besides their identification in bacterial genomes, there is also growing interest in determining the functionality of C. difficile prophages, i.e., their capacity to escape their host and reinfect a different strain, thereby promoting genomic evolution and horizontal transfer of genes through transduction, for example of antibiotic resistance genes. There is also some interest in using therapeutic phages to fight C. difficile infections.The objective of this chapter is to share with the broader C. difficile research community the expertise we developed in the study of C. difficile temperate phages. In this chapter, we describe a general "pipeline" comprising a series of experiments that we use in our lab to identify, induce, isolate, propagate, and characterize prophages. Our aim is to provide readers with the necessary basic tools to start studying C. difficile phages.

Phage sensitivity and prophage carriage in Staphylococcus aureus isolated from foods in Spain and New Zealand.

Bacteriophages (phages) are a promising tool for the biocontrol of pathogenic bacteria, including those contaminating food products and causing infectious diseases. However, the success of phage preparations is limited by the host ranges of their constituent phages. The phage resistance/sensitivity profile of eighty seven Staphylococcus aureus strains isolated in Spain and New Zealand from dairy, meat and seafood sources was determined for six phages (Φ11, K, ΦH5, ΦA72, CAPSa1 and CAPSa3). Most of the S. aureus strains were sensitive to phage K (Myoviridae) and CAPSa1 (Siphoviridae) regardless of their origin. There was a higher sensitivity of New Zealand S. aureus strains to phages isolated from both Spain (ΦH5 and ΦA72) and New Zealand (CAPSa1 and CAPSa3). Spanish phages had a higher infectivity on S. aureus strains of Spanish dairy origin, while Spanish strains isolated from other environments were more sensitive to New Zealand phages. Lysogeny was more prevalent in Spanish S. aureus compared to New Zealand strains. A multiplex PCR reaction, which detected ΦH5 and ΦA72 sequences, indicated a high prevalence of these prophages in Spanish S. aureus strains, but were infrequently detected in New Zealand strains. Overall, the correlation between phage resistance and lysogeny in S. aureus strains was found to be weak.

Bacteriophages with potential to inactivate Salmonella Typhimurium: Use of single phage suspensions and phage cocktails.

The aim of this study was to compare the dynamics of three previously isolated bacteriophages (or phages) individually (phSE-1, phSE-2 and phSE-5) or combined in cocktails of two or three phages (phSE-1/phSE-2, phSE-1/phSE-5, phSE-2/phSE-5 and phSE-1/phSE-2/phSE-5) to control Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) in order to evaluate their potential application during depuration. Phages were assigned to the family Siphoviridae and revealed identical restriction digest profiles, although they showed a different phage adsorption, host range, burst size, explosion time and survival in seawater. The three phages were effective against S. Typhimurium (reduction of ∼2.0 log CFU/mL after 4h treatment). The use of cocktails was not significantly more effective than the use of single phages. A big fraction of the remained bacteria are phage-resistant mutants (frequency of phage-resistant mutants 9.19×10(-5)-5.11×10(-4)) but phage- resistant bacterial mutants was lower for the cocktail phages than for the single phage suspensions and the phage phSE-1 presented the highest rate of resistance and phage phSE-5 the lowest one. The spectral changes of S. Typhimurium resistant and phage-sensitive cells were compared and revealed relevant differences for peaks associated to amide I (1620cm(-1)) and amide II (1515cm(-1)) from proteins and from carbohydrates and phosphates region (1080-1000cm(-1)). Despite the similar efficiency of individual phages, the development of lower resistance indicates that phage cocktails might be the most promising choice to be used during the bivalve depuration to control the transmission of salmonellosis.

Characterization of a novel Achromobacter xylosoxidans specific siphoviruse: phiAxp-1.

Bacteriophages have recently been considered as an alternative biocontrol tool because of the widespread occurrence of antimicrobial-resistant Achromobacter xylosoxidans. Herein, we isolated a virulent bacteriophage (phiAxp-1) from a water sample of the Bohai sea of China that specifically infects A. xylosoxidans. Transmission electron microscopy revealed that phage phiAxp-1 belongs to the Siphoviridae. We sequenced the genome of phiAxp-1, which comprises 45,045 bp with 64 open reading frames. Most of the proteins encoded by phiAxp-1 have no similarity to sequences in the public databases. Twenty-one proteins with assigned functions share weak homology with those of other dsDNA bacteriophages infecting diverse hosts, such as Burkholderia phage KL1, Pseudomonas phage 73, Pseudomonas phage vB_Pae-Kakheti25, Pseudomonas phage vB_PaeS_SCH_Ab26, Acinetobacter phage IME_AB3 and Achromobacter phage JWX. The genome can be divided into different clusters for the head and tail structure, DNA replication and mazG. The sequence and genomic organization of bacteriophage phiAxp-1 are clearly distinct from other known Siphoviridae phages; therefore, we propose that it is a member of a novel genus of the Siphoviridae family. Furthermore, one-step growth curve and stability studies of the phage were performed, and the specific receptor of phiAxp-1 was identified as the lipopolysaccharide of A. xylosoxidans.

Isolation and Characterization of the Lytic Cold-Active Bacteriophage MYSP06 from the Mingyong Glacier in China.

As unique ecological systems, glaciers are characterized by low temperatures and low nutrient levels, which allow them to be considered as "living fossils" for the purpose of researching the evolution of life and the environmental evolution of the earth. Glaciers are also natural microbial "reservoirs". In this work, a lytic cold-active bacteriophage designated MYSP06 was isolated from Janthinobacterium sp. MYB06 from the Mingyong Glacier in China, and its major characteristics were determined. Electron microscopy revealed that bacteriophage MYSP06 had an isometric head (74 nm) and a long tail (10 nm in width, 210 nm in length). It was classified as a Siphoviridae with an approximate genome size of 65­70 kb. A one-step growth curve revealed that the latent and burst periods were 95 and 65 min, respectively, with an average burst size of 16 bacteriophage particles per infected cell. The bacteriophage particles (100 %) adsorbed to the host cells within 10 min after infection. Moreover, the pH value and thermal stability of bacteriophage MYSP06 were also investigated. The maximum stability of the bacteriophage was observed at the optimal pH 7.0, and the bacteriophage became completely unstable at the extremely alkaline pH 11.0; however, it was comparatively stable at the acidic alkaline pH 6.0. As MYSP06 is a cold-active bacteriophage with a lower production temperature, its characterization and its relationship with its host Janthinobacterium sp. MYB06 deserve further study.