Replication and inheritance of Nocardia plasmid pC1

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Nocardia sp. C-14-1 efficiently degrades long-chain alkanes and succinonitrile.
• Characterization of indigenous plasmids is crucial for understanding microbial catabolic capabilities.

Purpose of the Study:

• To characterize the indigenous plasmid pC1 from Nocardia sp. C-14-1.
• To identify genes responsible for plasmid replication and stability.

Main Methods:

• Nucleotide sequencing of plasmid pC1.
• Bioinformatic analysis to predict open reading frames (ORFs).
• Functional analysis of the replication protein (Rep(pC1)) in heterologous hosts (E. coli, Nocardia, Rhodococcus).

Main Results:

• Plasmid pC1 is 5841 bp and contains five ORFs, including a DNA recombinase and Rep(pC1).
• Rep(pC1) shows homology to theta-type replication proteins from Rhodococcus.
• The rep(pC1) gene is essential for autonomous replication in Nocardia and Rhodococcus, but plasmids solely containing rep(pC1) exhibit unstable inheritance.

Conclusions:

• The rep(pC1) gene is a key determinant for plasmid replication in Nocardia and Rhodococcus.
• Additional genetic elements on pC1 are likely required for stable plasmid inheritance.
• Nocardia and Rhodococcus plasmids can be classified into four groups based on Rep protein comparison.