First report of linear megaplasmids in the genus Micrococcus

Area of Science:

• Microbiology
• Genetics
• Environmental Science

Background:

• High-altitude wetlands (above 4200m) in Argentina represent extreme, pristine environments.
• Micrococcus species are found in diverse environments, including extreme ones.

Purpose of the Study:

• To characterize linear megaplasmids found in Micrococcus strains from high-altitude wetlands.
• To investigate the genetic relationship of these strains and the function of their plasmids.

Main Methods:

• Isolation and characterization of linear megaplasmids (pLMA1, pLMH5, pLMV7).
• Lambda exonuclease treatment to assess terminal protein attachment.
• Electrophoretic mobility, Southern analysis, and restriction endonuclease digestion for plasmid comparison.
• 16S rDNA sequencing for phylogenetic analysis.
• BOX-PCR for strain typing.
• Generation of plasmid-deficient strains to study antibiotic resistance.

Main Results:

• Three linear megaplasmids (pLMA1, pLMH5, pLMV7) were identified in Micrococcus sp. A1, H5, and V7.
• All plasmids exhibited resistance to lambda exonuclease, indicating covalently attached terminal proteins.
• pLMA1 and pLMH5 were indistinguishable despite isolation from different locations.
• Phylogenetic analysis suggested a close relationship to Micrococcus luteus.
• Plasmid-deficient strains showed reduced erythromycin resistance.

Conclusions:

• The identified linear megaplasmids are stable and potentially widespread in high-altitude Micrococcus populations.
• These plasmids play a role in conferring antibiotic resistance, specifically to erythromycin.
• The study provides insights into the genetic makeup and adaptive strategies of microorganisms in extreme environments.