Compositional biases of bacterial genomes and evolutionary implications

Area of Science:

• Genomics
• Bioinformatics
• Evolutionary Biology

Background:

• Genome composition exhibits biases in short oligonucleotide frequencies.
• These biases can be characteristic of specific species or groups.
• Understanding these patterns is crucial for phylogenetic analysis and evolutionary studies.

Purpose of the Study:

• To compare genome-wide compositional biases and oligonucleotide distributions across diverse prokaryotes.
• To define and analyze the concept of a "genome signature" based on dinucleotide relative abundance profiles.
• To investigate the evolutionary and phylogenetic implications of these genomic signatures.

Main Methods:

• Analysis of complete and partial genomic sequences from 15 diverse prokaryotes.
• Calculation of dinucleotide relative abundance profiles (rhoXY*) for 50-kb contigs.
• Comparison of genome signatures between different species and within the same genome.
• Identification and quantification of specific di- and tetranucleotide biases.

Main Results:

• A consistent dinucleotide relative abundance profile, termed the "genome signature," was observed within individual prokaryotic genomes.
• Differences between genome signatures of different species consistently exceeded differences within the same genome.
• Specific biases were identified, such as CpG underrepresentation in thermophiles and TA underrepresentation across many prokaryotes.
• Methanococcus jannaschii exhibited extreme underrepresentation of CTAG tetranucleotides.

Conclusions:

• The genome signature serves as a reliable marker for distinguishing between prokaryotic species and can highlight evolutionary relationships.
• Observed biases provide insights into genome compositional flux and potential evolutionary pressures.
• Genome signatures have potential applications as a chronometer for molecular phylogeny and understanding the early evolution of life.