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The host-dependent restriction of growth of an RNA coliphage FI
Abstract:
Phage FIC is a spontaneous host-dependent mutant of phage FI which is classified into the fourth group of RNA Escherichia coli phages (RNA coliphages). The mutant phage (FIC) grows normally in E. coli strain Q13 (permissive host), but poorly in strain A/lambda (non-permissive host) (9). Attempts to elucidate the regulatory mechanism of growth of the mutant phage in the non-permissive host revealed the following: (a) growth of the mutant phage was specifically restricted in E. coli strains that have certain suppressor genes for amber mutation; (b) the mutant phage RNA (FIC-RNA) could not produce progeny in the spheroplasts of the non-permissive host; (c) adsorption of the mutant phage to, and penetration of the mutant phage RNA into, the non-permissive host were normal; and (d) biosynthesis of the phage-specific late protein and RNA did not occur in the non-permissive host. Based on these results we conclude that phage FIC is a spontaneous azure-type mutant of the fourth group of RNA coliphage FI.
Insights
Phage FIC, an RNA coliphage mutant, shows restricted growth in specific Escherichia coli strains. This restriction is linked to suppressor genes and prevents progeny production, protein, and RNA biosynthesis.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Phage FIC is a host-dependent mutant of RNA coliphage FI.
- It exhibits differential growth in Escherichia coli strains, growing poorly in non-permissive hosts.
Purpose of the Study:
- To investigate the regulatory mechanism behind the restricted growth of phage FIC in non-permissive E. coli hosts.
- To characterize the nature of the host-dependent mutation in phage FIC.
Main Methods:
- Comparative growth studies of phage FIC in permissive (E. coli Q13) and non-permissive (E. coli A/lambda) hosts.
- Analysis of phage FIC replication in spheroplasts of non-permissive hosts.
- Investigation of phage adsorption and RNA penetration.
- Examination of phage-specific protein and RNA biosynthesis.
Main Results:
- Phage FIC growth is specifically restricted in E. coli strains possessing suppressor genes for amber mutations.
- Progeny phage RNA production is inhibited in spheroplasts of the non-permissive host.
- Adsorption and RNA penetration into the non-permissive host are not impaired.
- Biosynthesis of phage-specific late proteins and RNA is blocked in the non-permissive host.
Conclusions:
- Phage FIC is identified as a spontaneous azure-type mutant of RNA coliphage FI.
- The restriction mechanism involves a block in late gene expression, likely due to interaction with host suppressor gene products.
- The mutation affects a critical step in viral replication within specific E. coli genetic backgrounds.