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Isolation and characterization of two types of actinophages infecting Streptomyces scabies MR13
A el-S el-Sayed1, G el-Didamony, K Mansour
1Department of Botany, Faculty of Science, Zagazig University, Zagazig, Egypt.
Abstract:
Two types of actinophages, phi S and phi L, were isolated from soil samples by using Streptomyces scabies MR13, a potato scab pathogen, as an indicator strain. The phages were partially characterized according to their physicochemical properties, plaques and particles morphology and their host-range. The host-range of these phages was narrow for phi S and wide for phi L. The adsorption rate constants of the phi S and phi L were 3.44 x 10(-9) and 3.18 x 10(-9) ml/min, and their burst sizes were 1.61 and 3.75 virions, respectively. One-step growth indicated that phi S and phi L have a latent period of 30 min followed by a rise period of 30 min. The temperate character of these phages was tested in other isolates of Streptomyces. Four of the phages (phi SS3, phi SS12, phi SS13 and phi SS17) were identified as temperate phages, since they were able to lysogenize SS3, SS12, SS13 and SS17. phi SS3, phi SS12 and phi SS13 were homoimmune, and they were heteroimmune with respect to phi SS17. The restriction barriers of lysogenic isolates (SS12, SS13 and SS17) interfered with the blockage of plaques formation by phages (phi SS12, phi SS13 or phi SS17) propagated on them, about 75% of lysogenic isolates had restriction systems. The exposure of the lysogenic isolates (SS12, SS13 and SS17) to UV-irradiation prevented the possible restriction barriers of these isolates, and these barriers could be overcome.
Insights
Two actinophages, phi S and phi L, were isolated and characterized. Some Streptomyces phages exhibited temperate characteristics and restriction-modification systems, which could be overcome by UV irradiation.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Actinophages are viruses that infect actinomycetes, including plant pathogens like Streptomyces scabies.
- Understanding phage-host interactions is crucial for phage therapy and microbial genetics.
Purpose of the Study:
- To isolate and characterize novel actinophages from soil samples.
- To investigate the temperate nature and host interactions of isolated phages.
Main Methods:
- Isolation of actinophages using Streptomyces scabies MR13 as an indicator strain.
- Characterization of physicochemical properties, plaque morphology, particle morphology, and host range.
- One-step growth curve analysis to determine latent and rise periods.
- Lysogenization assays and homo/heteroimmunity tests.
- Investigation of restriction-modification systems in lysogenic isolates.
Main Results:
- Two actinophages, phi S (narrow host range) and phi L (wide host range), were isolated and characterized.
- Phi S and phi L showed adsorption rates of 3.44 x 10(-9) and 3.18 x 10(-9) ml/min, with burst sizes of 1.61 and 3.75 virions, respectively.
- A latent period of 30 min followed by a 30 min rise period was observed for both phages.
- Four phages (phi SS3, phi SS12, phi SS13, phi SS17) were identified as temperate, with phi SS3, phi SS12, and phi SS13 being homoimmune.
- Restriction barriers were present in approximately 75% of lysogenic isolates, interfering with phage plaque formation, but could be overcome by UV irradiation.
Conclusions:
- The study successfully isolated and characterized two novel actinophages, phi S and phi L.
- The findings highlight the presence of temperate phages within Streptomyces populations and their associated restriction-modification systems.
- UV irradiation can be used to overcome phage restriction barriers in lysogenic Streptomyces isolates.
