Molecular phylogenetics before sequences: oligonucleotide catalogs as k-mer spectra

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Bioinformatics

Background:

• Carl Woese's pioneering work from 1971-1985 utilized oligonucleotide catalogs of 16S/18S ribosomal RNAs (rRNAs) from over 400 organisms.
• These data, despite imperfections, yielded crucial insights into the structure, function, and evolution of rRNA, leading to the recognition of a third domain of life and the bacterial phylogenetic backbone.

Purpose of the Study:

• To re-examine the phylogenetic signal within historical oligonucleotide catalogs in the context of modern alignment-free k-mer phylogenetics.
• To assess the aims, successes, and limitations of this early phase of molecular phylogenetics and computational biology.

Main Methods:

• Computationally generated oligonucleotide sets (e-catalogs) from 16S/18S rRNA sequences.
• Calculated pairwise distances using D 2 statistics.
• Constructed distance trees and compared them with alignment-based and k-mer trees.

Main Results:

• Demonstrated that oligonucleotide catalogs retain significant phylogenetic signal, validating Woese's early discoveries.
• The re-analysis provides a comparative performance assessment against contemporary phylogenetic methods.
• Highlighted the instructive value of this historical approach for modern computational molecular biology.

Conclusions:

• Early oligonucleotide catalog data possess substantial phylogenetic information, supporting foundational discoveries in microbial evolution and taxonomy.
• Modern computational approaches, including k-mer analysis, can effectively re-evaluate historical molecular data.
• This study underscores the enduring relevance of early molecular phylogenetics for understanding evolutionary history.