Bringing them together: plasmid pMV158 rolling circle replication and conjugation under an evolutionary perspective

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Rolling circle-replicating plasmids are prevalent in Gram-positive bacteria, carrying essential genes for replication, control, mobilization, and DNA synthesis.
• The streptococcal plasmid pMV158 serves as a model for studying promiscuous plasmid families, particularly their mobilization mechanisms.

Purpose of the Study:

• To analyze the mobilization functions of the pMV158 plasmid family, focusing on the MOBV relaxase and its origin of transfer (oriT).
• To investigate the diversity of origin of transfer (oriT) and single-strand origin (sso) sequences within the MOBV1 plasmid subfamily.
• To explore the association between rolling-circle replication initiator families (Rep_1 and Rep_2) and their preferred bacterial hosts, as well as their link to MOBV1 relaxases.

Main Methods:

• Comparative analysis of plasmid sequences to identify and classify oriT and sso types.
• Phylogenetic analysis of MOBV1 relaxases and replication initiator proteins.
• Bioinformatic assessment of plasmid distribution across bacterial orders.

Main Results:

• Three distinct oriT sequence groups (pMV158, pT181, p1414) and four sso types (ssoA, ssoU, ssoW, ssoT) were identified within the MOBV1 subfamily.
• Plasmids with Rep_2 initiators are more common in Lactobacillales, while Rep_1 initiators favor Bacillales.
• MOBV1 relaxases associated with Rep_2 initiators show distinct clustering compared to those linked with Rep_1 plasmids.
• MOBV1 plasmids are mobilizable and exhibit broad host range plasticity by utilizing various conjugative systems.

Conclusions:

• The study clarifies the diversity of mobilization and replication origins in rolling circle plasmids.
• Host range plasticity is influenced by the promiscuous recognition of oriT sequences and replication origins.
• MOBV1 plasmids are exclusively mobilizable, relying on diverse conjugative apparatuses for transfer.