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Understanding the Impact of Temperate Bacteriophages on Their Lysogens Through Transcriptomics
Published on: January 5, 2024
Identification of tail genes in the temperate phage 16-3 of Sinorhizobium meliloti 41
Veronika Deák1, Rita Lukács, Zsuzsanna Buzás
1Department of Genetics and Molecular Biology, Faculty of Sciences, University of Pécs, H-7601 Pécs, Hungary.
Abstract:
Genes encoding the tail proteins of the temperate phage 16-3 of the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti 41 have been identified. First, a new host range gene, designated hII, was localized by using missense mutations. The corresponding protein was shown to be identical to the 85-kDa tail protein by determining its N-terminal sequence. Electron microscopic analysis showed that phage 16-3 possesses an icosahedral head and a long, noncontractile tail characteristic of the Siphoviridae. By using a lysogenic S. meliloti 41 strain, mutants with insertions in the putative tail region of the genome were constructed and virion morphology was examined after induction of the lytic cycle. Insertions in ORF017, ORF018a, ORF020, ORF021, the previously described h gene, and hII resulted in uninfectious head particles lacking tail structures, suggesting that the majority of the genes in this region are essential for tail formation. By using different bacterial mutants, it was also shown that not only the RkpM and RkpY proteins but also the RkpZ protein of the host takes part in the formation of the phage receptor. Results for the host range phage mutants and the receptor mutant bacteria suggest that the HII tail protein interacts with the capsular polysaccharide of the host and that the tail protein encoded by the original h gene recognizes a proteinaceous receptor.
Insights
Researchers identified genes for tail proteins in Sinorhizobium meliloti phage 16-3. The HII tail protein interacts with host capsular polysaccharide, while another tail protein recognizes a protein receptor, crucial for phage infection.
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Temperate phage 16-3 infects the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti.
- Understanding phage-host interactions is crucial for microbial ecology and biotechnology.
Purpose of the Study:
- Identify genes responsible for the tail structure and host interaction of phage 16-3.
- Elucidate the roles of specific tail proteins in phage assembly and receptor recognition.
Main Methods:
- Genetic analysis using missense mutations and insertion mutagenesis in S. meliloti.
- N-terminal sequencing of phage tail proteins.
- Electron microscopy for virion morphology analysis.
- Construction and analysis of bacterial receptor mutants.
Main Results:
- Identified host range gene hII encoding an 85-kDa tail protein.
- Demonstrated that genes ORF017, ORF018a, ORF020, ORF021, h, and hII are essential for tail formation.
- Showed that host proteins RkpM, RkpY, and RkpZ are involved in phage receptor formation.
- Proposed that HII tail protein interacts with capsular polysaccharide, and the 'h' gene product recognizes a protein receptor.
Conclusions:
- The majority of genes in the identified region are essential for phage 16-3 tail assembly.
- Specific tail proteins mediate interactions with distinct components of the S. meliloti cell surface, influencing host range and infection.
