Variability of Inverted Repeats in All Available Genomes of Bacteria.

Area of Science:

• Genomics and Bioinformatics
• Molecular Biology
• Evolutionary Biology

Background:

• Noncanonical nucleic acid secondary structures, particularly cruciforms from inverted repeats (IRs), play crucial biological roles.
• Previous studies highlighted the significance of IRs in various organisms, including humans.

Purpose of the Study:

• To comprehensively analyze the frequencies, lengths, and genomic localizations of IRs across all accessible bacterial genomes.
• To investigate the correlation between IR abundance and bacterial lifestyle or environmental adaptation.

Main Methods:

• Utilized the Palindrome analyser tool to systematically identify and quantify IRs in 1,565 bacterial genome sequences.
• Performed statistical analysis to determine IR frequencies, distribution patterns, and associations with genomic features and organism characteristics.

Main Results:

• Identified over 242 million IRs across all analyzed bacterial genomes, confirming their genomic ubiquity.
• Observed significant variations in IR frequencies among different bacterial evolutionary groups, with highest in Tenericutes and lowest in Alphaproteobacteria.
• Found IRs are enriched near genes, regulatory elements, tRNA, tmRNA, and rRNA, indicating roles in genome maintenance, replication, and transcription; high IR frequency correlated with endosymbiotic, antibiotic-producing, or pathogenic lifestyles, while low frequency associated with thermophilic organisms.

Conclusions:

• This study provides the first complete analysis of IRs in all sequenced bacterial genomes, revealing their widespread presence and nonrandom distribution.
• The enrichment of IRs in regulatory regions underscores their importance in fundamental cellular processes and bacterial adaptation.
• The findings offer a valuable resource for researchers studying bacterial genomics and manipulating these regulatory sequences.