Optical mapping reveals a large genetic inversion between two methicillin-resistant Staphylococcus aureus strains

Area of Science:

• Microbiology
• Genomics
• Bacterial Evolution

Background:

• Staphylococcus aureus is a clinically significant bacterium known for its adaptability and evolution through genetic changes.
• Identifying novel genomic elements and rearrangements in bacteria is challenging without whole-genome sequencing.
• Optical mapping offers a high-resolution method for creating in situ ordered restriction maps of bacterial genomes.

Purpose of the Study:

• To utilize optical mapping for identifying and characterizing genomic rearrangements in Staphylococcus aureus.
• To specifically identify and locate a large genetic inversion between two S. aureus strains, NRS387 (USA800) and FPR3757 (USA300).

Main Methods:

• Employed optical mapping to generate high-resolution genomic restriction maps.
• Performed comparative genomics by comparing optical maps to in silico restriction maps of known genome sequences.
• Confirmed identified genomic inversions and junction sites using site-specific PCR and DNA sequencing.

Main Results:

• Successfully identified and characterized a genetic inversion of approximately 500 kb between S. aureus strains NRS387 and FPR3757.
• Located the approximate positions of the inversion within the bacterial genome.
• Discovered IS1181 elements and 73-bp inverted repeat sequences at the junction sites in the NRS387 strain, suggesting a mechanism for the inversion.

Conclusions:

• Optical mapping is an effective tool for detecting large-scale genomic rearrangements like inversions in bacteria.
• The identified inversion and its associated repeat sequences provide insights into the mechanisms driving Staphylococcus aureus genome evolution.
• This study demonstrates the utility of optical mapping in comparative genomics and understanding bacterial plasticity.