Comparative analysis of eight Arthrobacter plasmids.

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Arthrobacter species are widespread in diverse environments.
• The plasmids of Arthrobacter and their role in horizontal gene transfer remain largely uncharacterized.

Purpose of the Study:

• To identify core maintenance genes (replication, segregation, conjugation) in eight Arthrobacter plasmids.
• To investigate the potential for horizontal gene transfer mediated by Arthrobacter plasmids.

Main Methods:

• Comparative analysis of eight plasmids from five Arthrobacter strains.
• Identification of putative genes involved in plasmid maintenance using sequence similarity searches.
• Cluster analysis of identified genes.
• Phylogenetic comparison of concatenated maintenance genes.

Main Results:

• No typical replication origins or rep genes were found, though some iteron-like sequences were present.
• All eight plasmids possess putative conjugation systems, including relaxase, coupling proteins, and type IV secretion system components, potentially representing three distinct systems.
• Putative parA partitioning genes were identified in all plasmids, and parB genes were present in most strains.
• Gene cluster analysis indicated that Arthrobacter genes often branch within existing plasmid maintenance gene families.
• Comparative analysis of concatenated maintenance genes suggests multiple evolutionary origins for these plasmids.

Conclusions:

• Arthrobacter plasmids harbor conserved conjugation and partitioning systems, suggesting a capacity for horizontal gene transfer.
• The absence of canonical replication genes points to unique replication mechanisms.
• The genetic diversity and evolutionary pathways of Arthrobacter plasmids are extensive.