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Ultrastructure of Escherichia coli cells infected with bacteriophage R17
Abstract:
Franklin, Richard M. (Institut de Recherches sur le Cancer, Villejuif, Seine, France), and Nicole Granboulan. Ultrastructure of Escherichia coli cells infected with bacteriophage R17. J. Bacteriol. 91:834-848. 1966-Ultrastructural changes in Escherichia coli cells infected with ribonucleic acid (RNA) bacteriophage R17 were studied under conditions of one-step growth. No morphological alterations were seen during the latent period. During the period of rapid viral synthesis, a fibrillar lesion surrounded by ribonucleoprotein particles was observed in a polar region. Late in infection, paracrystalline arrays of virions were found in over 90% of the cells. When protein synthesis was blocked by in over 90% of the cells. When protein synthesis was blocked by chloramphenicol at 20 min postinfection, allowing continued viral RNA synthesis without production of coat protein, a dense fibrillar area appeared in a paranuclear region. Cytochemical studies were done on cells embedded in hydroxypropyl methacrylate, a water-miscible embedding agent. The paracrystalline arrays of virions were digested after extensive treatment with either pepsin or ribonuclease. Shorter digestion with the pepsin resulted in better definition of the crystal regions. The fibrillar area found in chloramphenicol-treated cells was digested by ribonuclease but not by pepsin, and was also resistant to lead extraction. This region probably represents a pool of virus-specific RNA.
Insights
Researchers studied Escherichia coli infected with bacteriophage R17, observing viral RNA and protein synthesis. They identified distinct ultrastructural changes, including fibrillar lesions and paracrystalline arrays, crucial for understanding viral replication dynamics.
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Bacteriophage R17 is a ribonucleic acid (RNA) bacteriophage that infects Escherichia coli.
- Understanding the ultrastructural changes during viral infection is key to elucidating replication mechanisms.
Purpose of the Study:
- To investigate the ultrastructural alterations in Escherichia coli cells infected with bacteriophage R17.
- To characterize the morphology and composition of viral structures during different stages of infection.
Main Methods:
- One-step growth experiments were conducted on Escherichia coli infected with bacteriophage R17.
- Cells were analyzed using electron microscopy to observe ultrastructural changes.
- Cytochemical studies involved enzyme digestion (pepsin, ribonuclease) and lead extraction on embedded cells.
Main Results:
- No morphological changes were observed during the latent period of infection.
- During rapid viral synthesis, a polar fibrillar lesion with ribonucleoprotein particles appeared.
- Late in infection, paracrystalline arrays of virions were found in over 90% of cells.
- Chloramphenicol treatment led to a dense fibrillar area, likely representing virus-specific RNA, which was ribonuclease-sensitive.
Conclusions:
- Bacteriophage R17 infection induces specific ultrastructural changes in Escherichia coli.
- Paracrystalline arrays represent assembled virions, while the chloramphenicol-induced fibrillar area is likely a pool of viral RNA.
- These findings provide insights into the replication cycle and assembly of RNA bacteriophages.