Sequence relations among the IncY plasmid p15B, P1, and P7 prophages

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• Plasmids and bacteriophages are crucial genetic elements in microbial systems.
• Understanding the genomic relationship between plasmids and phages is essential for molecular biology research.
• Plasmid p15B, phage P1, and phage P7 are significant entities in microbial genetics.

Purpose of the Study:

• To analyze the structural and homologous relationships between plasmid p15B and the genomes of phage P1 and phage P7.
• To identify regions of nonhomology, substitution, and insertion in the heteroduplex molecules.
• To investigate the presence and significance of unique structural features, such as stem-loop structures and invertible segments.

Main Methods:

• Electron microscopic analysis of heteroduplex DNA molecules formed between plasmid p15B and phage P1.
• Electron microscopic analysis of heteroduplex DNA molecules formed between plasmid p15B and phage P7.
• Quantification of homologous and nonhomologous DNA segments.

Main Results:

• Heteroduplex analysis between p15B and P1 revealed 83% homology, with nine nonhomologous regions, eight substitutions, and two insertions.
• Heteroduplex analysis between p15B and P7 showed 83% homology, with eight shared nonhomologous regions, additional nonhomologies, and a 5-kb insertion (Tn902) in P7.
• Plasmid p15B possesses two distinct stem-loop structures, one unique and another substituting invertible segments and the cin recombinase gene found in P1 and P7.

Conclusions:

• Significant genomic homology exists between plasmid p15B and phages P1 and P7, indicating shared ancestry or genetic exchange.
• Specific regions of nonhomology, insertions (like Tn902), and unique structural elements (stem-loops, invertible segments) define the distinct identities of these genetic elements.
• The findings provide insights into the evolutionary dynamics and structural organization of these important microbial genetic entities.