Establishing the phylogeny of Prochlorococcus with a new alignment-free method

Area of Science:

• Marine microbiology
• Evolutionary biology
• Bioinformatics

Background:

• Prochlorococcus marinus is a globally abundant marine cyanobacterium with distinct low-light (LL) and high-light (HL) adapted ecotypes.
• Understanding the evolutionary relationships and phylogeny within Prochlorococcus is crucial for marine microbial ecology.
• The monophyletic status of strains SS120 and MIT9211 within Prochlorococcus phylogeny requires clarification.

Purpose of the Study:

• To develop and apply an alignment-free Natural Vector (NV) method, incorporating amino acid covariances, for robust phylogenetic analysis of Prochlorococcus.
• To systematically reconstruct the phylogeny of Prochlorococcus using both ribosomal proteome and 16S-23S rRNA sequence datasets.
• To investigate the evolutionary relationship between Prochlorococcus strains SS120 and MIT9211 and determine if they form a monophyletic group.

Main Methods:

• The study employed the Natural Vector (NV) method, an alignment-free approach, to represent biological sequences.
• Amino acid covariances were integrated into the NV method to enhance sequence representation and phylogenetic inference.
• Hausdorff distance was computed between clades using the new NV method to quantify sequence dissimilarity.
• Phylogenetic trees were reconstructed using both ribosomal proteome and 16S-23S rRNA datasets.
• Classification methods were applied to further inspect the relationship between strains SS120 and MIT9211.

Main Results:

• The enhanced Natural Vector method successfully reconstructed phylogenetic trees for Prochlorococcus.
• Analysis of ribosomal proteome and 16S-23S rRNA sequences using the NV method provided insights into Prochlorococcus phylogeny.
• Phylogenetic and classification results demonstrated that strain SS120 does not cluster with strain MIT9211.

Conclusions:

• The study presents a novel and effective Natural Vector-based method for phylogenetic analysis of microbial populations.
• The findings confirm that Prochlorococcus strains SS120 and MIT9211 do not constitute a monophyletic clade.
• This research contributes to a clearer understanding of Prochlorococcus evolutionary history and microbial phylogeny.