Horizontal gene transfers underpin ribose heterotrophy and central carbon metabolism remodeling in Gloeobacteraceae (Cyanobacteria)

Public genomic repositories enable large-scale reanalysis of evolutionary processes across deeply branching lineages. Using comparative genomics and phylogenetic analyses of publicly available cyanobacterial genomes, we investigate the evolutionary history of Gloeobacterales, an early-diverging cyanobacterial order distinguished by the absence of thylakoid membranes. We show that horizontal gene transfer has played a major role in shaping the central carbon metabolism of this lineage.
In Gloeobacteraceae, one of the two families within the order, we identify a complete ribose ABC importer and associated metabolic enzymes enabling ribose uptake and assimilation alongside photosynthesis, consistent with a photomixotrophic lifestyle. More broadly, core metabolic pathways—including the Calvin–Benson–Bassham cycle, the pentose phosphate pathway, and the Embden–Meyerhof–Parnas pathway—exhibit a mosaic structure resulting from the integration of foreign genes. Phylogenetic analyses indicate multiple independent transfer events from diverse bacterial donors, including other cyanobacteria and Pseudomonadota, with transferred genes dispersed across the genome.
These results reveal Gloeobacterales as a metabolically dynamic lineage shaped by recurrent gene acquisition and demonstrate how systematic reuse of public genomic data can uncover previously unrecognized patterns of metabolic evolution.