Simplification of Ribosomes in Bacteria with Tiny Genomes

Area of Science:

• Molecular Biology
• Genomics
• Microbiology

Background:

• Ribosomes are essential for protein synthesis and highly conserved across species.
• Some bacteria exhibit incomplete ribosomal protein sets, particularly in reduced genomes.

Purpose of the Study:

• To analyze ribosomal protein composition in small bacterial genomes.
• To identify frequently lost ribosomal proteins and their characteristics.
• To investigate the relationship between genome reduction, ribosomal protein loss, and ribosomal RNA reduction.

Main Methods:

• Analysis of ribosomal protein composition in 214 small bacterial genomes (<1 Mb).
• Identification of frequently lost ribosomal proteins and their location/contacts within the ribosome.
• Correlation analysis of protein loss and ribosomal RNA deletions.

Main Results:

• Ribosome composition is generally stable but shows variability in bacteria with reduced genomes.
• The large ribosomal subunit's protein composition is less conserved than the small subunit's.
• Frequently lost ribosomal proteins are surface-exposed with fewer interactions.
• Ribosomal RNA reduction is common, with deletions in free loops.
• Loss of the anti-Shine-Dalgarno sequence correlates with higher ribosomal protein loss.

Conclusions:

• Genome reduction in bacteria can lead to the loss of specific ribosomal proteins and RNA.
• Surface-exposed ribosomal proteins with fewer interactions are more prone to loss.
• Evolutionary correlated loss of ribosomal components occurs.
• The anti-Shine-Dalgarno sequence plays a role in maintaining ribosomal protein integrity.