Construction of an Escherichia coli-Rhodococcus shuttle vector and plasmid transformation in Rhodococcus spp

Area of Science:

• Microbiology
• Molecular Biology
• Genetic Engineering

Background:

• Rhodococcus species are important in various industrial applications but lack efficient genetic manipulation tools.
• Existing methods for Rhodococcus transformation are limited, hindering molecular studies and strain improvement.
• Development of a robust plasmid transformation system is crucial for advancing research in Rhodococcus.

Purpose of the Study:

• To develop a functional plasmid transformation system for Rhodococcus sp. strain H13-A.
• To construct and characterize a novel Escherichia coli-Rhodococcus shuttle plasmid.
• To establish efficient transformation protocols and determine the host range for Rhodococcus species.

Main Methods:

• Construction of a shuttle plasmid (pMVS301) by cloning a Rhodococcus DNA fragment into an E. coli plasmid.
• Transformation of Rhodococcus protoplasts using polyethylene glycol (PEG) assistance.
• Selection of transformants based on antibiotic resistance (thiostrepton and ampicillin).
• Plasmid isolation, restriction analysis, and replication studies in both E. coli and Rhodococcus.

Main Results:

• A 10.1-kb shuttle plasmid, pMVS301, was successfully constructed and shown to replicate in both E. coli and Rhodococcus.
• High transformation frequencies (up to 10^5 transformants per microgram DNA) were achieved in Rhodococcus sp. strain H13-A.
• The plasmid demonstrated a stable, independent replication in Rhodococcus and a host range including R. erythropolis, R. globulerus, and R. equi.
• Restriction analysis confirmed plasmid stability, and 14 unique restriction sites were mapped, useful for cloning.

Conclusions:

• A reliable plasmid transformation system for Rhodococcus species has been established.
• This system enables stable maintenance and replication of foreign DNA in Rhodococcus.
• This work represents the first report of plasmid transformation and heterologous gene expression in Rhodococcus.