Viral satellites and related MGEs shape the genomic plasticity of abundant open-ocean microbes

Activity: Talk and presentationAcademic presentationAcademic


Horizontal gene transfer is a key accelerant of microbial evolution promoting rapid diversification and adaptation through genomic plasticity. Highly abundant open ocean microbes such as Prochlorococcus and Pelagibacter possess heavily streamlined genomes and extensive pangenomes reflecting extensive gene exchange. Surprisingly, these streamlined organisms lack the capacity for conjugation and transformation, two of the most common modes of horizontal gene transfer.

Leveraging over 600 genomes - mostly of single cells - we revealed that Prochlorococcus harbors a diverse system of mobile genetic elements that appear to shape its considerable genomic plasticity. 70% of its flexible genes are predominantly organized within distinct genomic islands that have formed around a small set of tRNAs. The latter serve as integration hotspots for the majority of the mobile genetic elements. The elements themselves exhibit a high degree of mosaicism, and their hallmark genes suggest that they are integrative, self-replicating and regulated through stress signals. Moreover, many of the elements carry additional cargo including operons for the acquisition of nutrients and genes associated with viral defense underpinning their potential role in niche adaptation. We also found that many of these elements are highly enriched in either extracellular vesicle and viral fraction metagenomes, indicating that they can be efficiently transmitted between cells through these extracellular particles. As evidence of gene mobilization via these elements grows and if their dispersal through viral capsids and vesicles is found to be prevalent among free-living marine microbes, it could add a significant piece to the puzzle of what governs microbial evolution in the planet's largest habitat.
Event titleViruses of Microbes 2023
Event typeConference
LocationTbilisi, GeorgiaShow on map