Complete nucleotide sequence and comparative genomic analysis of microcin B17 plasmid pMccB17

Area of Science:

• Microbiology
• Genomics
• Bioinformatics

Background:

• Microcin B17 (MccB17) is a peptide antibiotic produced by Escherichia coli that inhibits DNA gyrase.
• The genes responsible for MccB17 biosynthesis and export are located on the microcin operon (mcb).
• The mcb operon was previously found on the IncFII plasmid pMccB17 in E. coli LP17 and later transferred to E. coli K-12.

Purpose of the Study:

• To perform a comprehensive sequence and bioinformatic analysis of the microcin plasmid pMccB17.
• To obtain a definitive DNA sequence of the mcb operon.
• To characterize the genetic content and evolutionary context of pMccB17.

Main Methods:

• Plasmid DNA extraction from E. coli K-12 strain RYC1000 [pMccB17].
• High-throughput sequencing using Illumina short-read technology (two runs).
• Sequence assembly into a single contig, gap closure via Sanger sequencing, and gene prediction/annotation (Prokka, BLAST).

Main Results:

• A complete circular DNA sequence of pMccB17 (69,190 bp) with 81 predicted genes was determined.
• The definitive sequence of the seven-gene mcb operon was established.
• The plasmid belongs to the F2:A-:B- replicon type with a MOBF12 conjugation system and shares backbone genes with other IncFII plasmids.
• Notably, pMccB17 lacks transposable elements and antibiotic resistance genes, and contains 25 genes of unknown function.

Conclusions:

• The complete genome sequence of pMccB17 provides a reference for microcin biosynthesis and plasmid biology.
• pMccB17 represents a unique IncFII plasmid lacking common mobile genetic elements and antibiotic resistance genes.
• The identified genes of unknown function warrant further investigation to elucidate their roles in plasmid biology or host interaction.