Epitranscriptional m6A modification of rRNA negatively impacts translation and host colonization in Staphylococcus...

Area of Science:

• Microbiology
• Molecular Biology
• Epitranscriptomics

Background:

• Macrolides, lincosamides, and streptogramin B (MLS) are crucial antibiotics, but bacterial resistance, often mediated by Erm methyltransferases, limits their efficacy.
• Erm enzymes methylate bacterial 23S rRNA at nucleotide A2058 (m6A2058), conferring resistance to MLS antibiotics.
• The functional consequences of this m6A epitranscriptomic mark on ribosome function and bacterial physiology remain largely unknown.

Purpose of the Study:

• To investigate the impact of m6A2058 modification on Staphylococcus aureus ribosome function, translational fidelity, and competitive fitness.
• To elucidate the physiological trade-offs associated with Erm-mediated MLS resistance beyond antibiotic resistance.

Main Methods:

• Utilized ribosome profiling (Ribo-Seq) to analyze global translation patterns in bacteria with m6A2058-modified versus unmodified ribosomes.
• Employed a dual-fluorescence reporter system to quantify ribosome occupancy and translational fidelity.
• Conducted competitive infection and colonization assays in vivo.

Main Results:

• Staphylococcus aureus strains with m6A2058-modified ribosomes exhibit impaired colonization and are outcompeted by strains with unmodified ribosomes during infection.
• The competitive disadvantage of m6A2058 ribosomes is evident primarily under antibiotic pressure.
• Ribosome profiling revealed disproportionate deregulation of genes involved in host interactions, metabolism, and information processing, linked to reduced translational capacity and fidelity.

Conclusions:

• The m6A2058 epitranscriptomic mark, while conferring MLS resistance, leads to a general "inefficient translation" phenotype.
• This inefficient translation impacts bacterial fitness and competitiveness, highlighting a significant trade-off for multidrug-resistant bacteria.
• Findings provide novel insights into the physiological costs of antibiotic resistance mechanisms.