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Phage and defective phage of strains of Myxococcus
Abstract:
1. Phage-like particles were found in the supernatants of cultures of strains of Myxococcus xanthus, M. virescens and M. fulvus. The largest number of such particles was associated with M. virescens V2. Most of the particles were similar in morphology to the virulent Myxococcus phage, MX-1. 2. Several new phages were isolated from soil and animal droppings. A new phage was isolated from cultures of M. virescens V2. All resembled phage MX-1 in morphology and were related to phage MX-1 serologically. One of these phage, om, was characterized by fractionation of its proteins by SDS-polyacrylamide gel electrophoresis and by analysis of restriction fragments of its DNA. The very close relatedness with MX-1 was confirmed by these techniques. Phage om, was found to exist in a state of pseudolysogeny with strains of M. virescens and M. fulvus. 3. Two types of bacteriocin-like activity were found associated with Myxococcus strains. In one case, the activity was extracted from chloroformkilled or from sonicated cells. In the second case it was associated with extracellular material. Strains of Salmonella and Cytophaga were found to be good indicators for this latter activity. These strains were found to be killed by phage MX-1. 4. The significance of these data for origin of the phages of myxococci are discussed and it is proposed that MX-1 and the newly isolated phages may be virulent mutants of a family of lysogenic phages.
Insights
New Myxococcus phages, similar to MX-1, were discovered in soil and animal droppings. These phages, along with bacteriocin-like activity, suggest virulent mutants may arise from lysogenic phage families.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Myxococcus species are known to harbor phage-like particles.
- The virulent Myxococcus phage, MX-1, serves as a reference for phage morphology.
Purpose of the Study:
- To investigate and characterize new phages associated with Myxococcus strains.
- To explore bacteriocin-like activities within Myxococcus populations.
- To understand the evolutionary origins of Myxococcus phages.
Main Methods:
- Isolation and culturing of Myxococcus strains from environmental samples (soil, animal droppings).
- Morphological analysis of phage-like particles using electron microscopy.
- Serological relatedness testing between isolated phages and MX-1.
- Biochemical characterization of phage om, including SDS-PAGE of proteins and DNA restriction fragment analysis.
- Assay for bacteriocin-like activity using indicator strains (Salmonella, Cytophaga).
Main Results:
- Phage-like particles were detected in Myxococcus xanthus, M. virescens, and M. fulvus cultures, with M. virescens V2 yielding the most.
- Several new phages, morphologically and serologically related to MX-1, were isolated.
- Phage om showed close relatedness to MX-1 via protein and DNA analysis and exhibited pseudolysogeny with M. virescens and M. fulvus.
- Two types of bacteriocin-like activities were identified, one intracellular and one extracellular, with Salmonella and Cytophaga as sensitive indicators.
Conclusions:
- The newly isolated phages are closely related to MX-1.
- Phage om demonstrates pseudolysogeny, indicating a complex relationship with its host.
- The findings support the hypothesis that MX-1 and related phages may originate from virulent mutants of lysogenic phage families.