• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.87-94
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• 2018

This study investigated the feasibility of the lytic, tailed Bacillus cereus-specific phage for use in a ferromagnetoelastic (FME) biosensor as a novel recognition element. The phage was immobilized at various concentrations through either direct adsorption or a combination of 11-mercapto-1-undecanoic acid (11-MUA) and [N-(3-dimethylaminopropyl)-N'-carbodiimide hydrochloride and N-hydroxysuccinimide (EDC/NHS)]. The effects of time and temperature on its lytic properties were investigated through the exposure of B. cereus (4 and 8 logCFU/ml) to the phage (8 logPFU/ml) for various incubation periods at $22^{\circ}C$ and at various temperatures for 30 and 60 min. As the phage concentration increased, both immobilization methods also significantly increased the phage density (p < 0.05). SEM images confirmed that the phage density on the FME platform corresponded to the increased phage concentration. As the combination of 11-MUA and EDC/NHS enhanced the phage density and orientation by up to 4.3-fold, it was selected for use. When various incubation was conducted, no significant differences were observed in the survival rate of B. cereus within 30 min, which was in contrast to the significant decreases observed at 45 and 60 min (p < 0.05). In addition, temperature exerted no significant effects on the survival rate across the entire temperature range. This study demonstrated the feasibility of the lytic, tailed B. cereus-specific phage as a novel recognition element for use in an FME biosensor. Thus, the phage could be placed on the surface of foods for at least 30 min without any significant loss of B. cereus, as a result of the inherent lytic activity of the B. cereus-specific phage as a novel recognition element.

• Food Science and Preservation
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• v.30 no.1
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• pp.42-51
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• 2023

This study aimed to characterize a lytic Salmonella Typhimurium-specific (ST) phage and its biofilm control capability against S. Typhimurium biofilm on polypropylene surface. ST phage was isolated, propagated, and purified from water used in a slaughterhouse. The morphology of ST phage was observed via transmission electron microscopy. Its bactericidal effect was evaluated by determining bacterial concentrations after the phage treatment at various multiplicities of infection (MOIs) of 0.01, 1.0, and 100. Once the biofilm was formed on the polypropylene tube after incubation at 37℃ for 48 h, the phage was treated and its antibiofilm capability was determined using crystal violet staining and plate count method. The phage was isolated and purified at a final concentration of ~11 log PFU/mL. It was identified as a myophage with an icosahedral head (~104 nm) and contractile tail (~90-115 nm). ST phage could significantly decrease S. Typhimurium population by ~2.8 log CFU/mL at an MOI of 100. After incubation for 48 h, biofilm formation on polypropylene surface was confirmed with a bacterial population of ~6.9 log CFU/cm². After 1 h treatment with ST phage, the bacterial population in the biofilm was reduced by 2.8 log CFU/cm². Therefore, these results suggest that lytic ST phage as a promising biofilm control agent for eradicating S. Typhimurium biofilm formed on food contact surfaces.

• Journal of fish pathology
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• v.11 no.2
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• pp.137-141
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• 1998

Temperate phages were effectively induced from presumptive lysogenized cells of 96 strains out of 111 strains of L. garvieae No. 44 strains (phage type B) as the host cell. Similar cultures in distilled water-based TSB did not induce lytic infection in these cells. These temperate phages were also effectively induced by ultraviolet irradiation. All phages isolated were lytic only to L. garvieae No. 44 strain and the lytic nature was different from those of PLgY, PLgW, and PLgS. The virions appeared extracellularly after 1h of induction culture and increased in number until reaching the maximum of $10^6$ PFU/ml after 12h. This phage production was lower than that ($10^{10}$ PFU/ml) of the virulent phage.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.262-270
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• 2007

Of the twelve lytic bacteriophages recovered from five different fermenting cucumber tanks that were inoculated with Pediococcus sp. LA0281, a lytic phage, ${\phi}ps05$, was characterized in the present study. The plaques were mostly clear and round-shaped on the lawn of starter strain, indicating lytic phage. Overall appearance indicated that it belongs to the Siphoviridae family or Bradley's group B1, with a small isometric head and a flexible noncontractile tail with swollen base plate. The average size was found to be 51.2 nm in head diameter and 11.6 nm wide ${\times}$ 129.6 nm long for the tail. The single-step growth kinetics curve showed that the eclipse and the latent period were 29 min and 34 min, respectively, and an average burst size was calculated to be 12 particles per infective center. The optimum proliferating temperature ($35^{\circ}C$) was slightly lower than that of cell growth ($35\;to\;40^{\circ}C$). The structural proteins revealed by SDS-PAGE consisted of one main protein of 33 kDa and three minor proteins of 85, 58, and 52 kDa. The phage genome was a linear double-stranded DNA without cohesive ends. Based on the single and double digestion patterns obtained by EcoRI, HindIII, and SalI, the physical map was constructed. The overall size of the phage genome was estimated to be 24.1 kb. The present report describes the presence of a lytic phage active against a commercial starter culture Pediococcus sp. LA0281 in cucumber fermentation, and a preliminary study characterizes the phage on bacterial successions in the process of starter-added cucumber fermentation.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1613-1620
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• 2012

Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of many economically important crops. Since there is no promising control strategy for bacterial wilt, phage therapy could be adopted using virulent phages. We used phage PE204 as a model lytic bacteriophage to investigate its biocontrol potential for bacterial wilt on tomato plants. The phage PE204 has a short-tailed icosahedral structure and double-stranded DNA genome similar to that of the members of Podoviridae. PE204 is stable under a wide range of temperature and pH, and is also stable in the presence of the surfactant Silwet L-77. An artificial soil microcosm (ASM) to study phage stability in soil was adopted to investigate phage viability under a controlled system. Whereas phage showed less stability under elevated temperature in the ASM, the presence of host bacteria helped to maintain a stable phage population. Simultaneous treatment of phage PE204 at $10^8$ PFU/ml with R. solanacearum on tomato rhizosphere completely inhibited bacterial wilt occurrence, and amendment of Silwet L-77 at 0.1% to the phage suspension did not impair the disease control activity of PE204. The biocontrol activities of phage PE204 application onto tomato rhizosphere before or after R. solanacearum inoculation were also investigated. Whereas pretreatment with the phage was not effective in the control of bacterial wilt, post-treatment of PE204 delayed bacterial wilt development. Our results suggested that appropriate application of lytic phages to the plant root system with a surfactant such as Silwet L-77 could be used to control the bacterial wilt of crops.

• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1704-1707
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• 2007

Monitoring of the phage-host system of Microlunatus phosphovorus indigenous in activated sludge was attempted. A laboratory-scale activated sludge process was operated for 5 weeks with synthetic wastewater. The phage-host system population in the process was monitored by plaque assay and FISH methods at every 3 days. During the process operation, the phage-host system populations were more or less steady, except for 1 week in the middle of the operation. In that period, initially M. phosphovorus decreased significantly and its lytic bacteriophages increased, and then M. phosphovorus increased back to its original level while its lytic bacteriophages decreased. This observation suggests that lytic bacteriophages should be considered as one of the biological factors affecting the bacterial population dynamics in activated sludge processes.

• Microbiology and Biotechnology Letters
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• v.11 no.1
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• pp.1-4
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• 1983

In order to determine a proper amount of sodium pyrophosphate (SPP) which protect Lactobacilli from phage attack, Lactobacillus casei YIT-9018 was grown in $Ca^{＋＋}$ free Murata medium having various concentrations of SPP after infections with phage Jl at different multiplicities of infection (MOI). it was found that the level of SPP to inhibit phage activity depended upon the level of MOIs. When the bacteria were infected by less than 10$^{-1}$ of MOI, 0.15% of SPP was sufficient, while with 10$^{0}$ of MOI, 0.175% of SPP was needed to inhibit the lytic activity completely.

• Microbiology and Biotechnology Letters
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• v.10 no.4
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• pp.253-258
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• 1982

Lactobacillus casei YIT 9018 was infected with phage J1 and subjected to grow in $Ca^{＋＋}$ -free MRT (spell out) medium under the presence of four different types of phosphates, sodium-metaphosphate,-pyrophos-phate,-dibasic phosphate, and potassium-phosphate. Among the phosphates tested, sodium pyrophosphate showed sufficient inhibition on the lytic activity of the phage at 0.1% level whereas other phosphate needed more than 0.2% for the same effect. When the concentration of sodium pyrophosphate increased to 0.17%, the bacteria could be protected from lysis until the second succeeding transfer.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1518-1522
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• 2006

In the present study, it was observed how the phage-host system that is naturally reproduced in activated sludge is affected by the host inoculation. The system of Microlunatus phosphovorus and its phages was selected as the phage-host system native to an activated sludge system operated for 19 days under sequencing anaerobic-aerobic conditions with glutamate as the main carbon source. The phage-host system related to M. phosphovorus was monitored by plaque assay for the phages and by fluorescent in situ hybridization (FISH) for the bacterial host. In addition, the whole phage structure was also monitored by pulsed-field gel electrophoresis (PFGE). During the first 9 days, the phage-host system was more or less steady at approx. 9% (FISH/ DAPI) for M. phosphovorus and approx. 10,000 PFU/ml for its lytic phages. Microlunatus phosphovorus JCM9379 was inoculated into the activated sludge on day 10. Right after the inoculation, M. phosphovorus was approx. 24% (FISH/DAPI) whereas its lytic phages dropped down to approx. 500 PFU/ ml. After the host inoculation (within 9 days), however, the phage-host system eventually reverted to its original level in each population. On the other hand, the whole phage structure was not significantly changed by M. phosphovorus inoculation but stable throughout the process operation. Only the minor change that four phage groups gradually became abundant after the host inoculation was observed.

• Journal of Microbiology and Biotechnology
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• v.28 no.11
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• pp.1946-1954
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• 2018

The aim of this study was to isolate and characterize a lytic Yersinia enterocolitica-specific phage (KFS-YE) as a biocontrol agent. KFS-YE was isolated and purified with the final concentration of ($11.72{\pm}0.03$) log PFU/ml from poultry. As observed by transmission electron microscopy, KFS-YE consisted of an icosahedral head and a contractile tail, and was classified in the Myoviridae family. KFS-YE showed excellent narrow specificity against Y. enterocolitica only. Its lytic activity was stable at wide ranges of pH (4-11) and temperature ($4-50^{\circ}C$). The latent period and burst size of KFS-YE were determined to be 45 min and 38 PFU/cell, respectively. KFS-YE showed relatively robust storage stability at -20, 4, and $22^{\circ}C$ for 40 weeks. KFS-YE demonstrated a bactericidal effect in vitro against Y. enterocolitica and provided excellent efficiency with a multiplicity of infection as low as 0.01. This study demonstrated the excellent specificity, stability, and efficacy of KFS-YE as a novel biocontrol agent. KFS-YE may be employed as a practical and promising biocontrol agent against Y. enterocolitica in food.